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Thread-Level Parallelism

1. int opta 1 int optr 0 int optR 0 int optc 0 int optC 0 int optF 0 timespec_t sample res int c while 1 c getopt argc argv arRcCF switch c case a opta 1 break case r optr 1 opta 0 break case R optR 1 opta 0 break case c optc 1 opta 0 break case C optC 1 opta 0 break case F optF 1 opta 0 break default return 1 if opta optr if clock_gettime CLOCK_REALTIME amp sample showtime sample CLOCK_REALTIME value else perror clock_gettime CLOCK_REALTIME if opta optR if clock_getres CLOCK_REALTIME amp res showtime res CLOCK_REALTIME units else perror clock_getres CLOCK_REALTIME if opta optc if clock_gettime CLOCK_SGI_CYCLE sample showtime sample CLOCK_SGI_CYCLE value else perror clock_gettime CLOCK_SGI_CYCLE if opta optc Timer Facilities if clock_getres CLOCK_SGI_CYCLE amp res showtime res CLOCK_SGI_CYCLE units else perror clock_getres CLOCK_SGI_CYCLE if opta optF if clock_getres CLOCK_SGI_FAST res showtime res CLOCK_SGI_FAST units else perror clock_get res CLOCK_SGI_FAST The real time clock CLOCK_REALTIME can shift backward or jump forward under the influence of adj
2. The program sends Program to Demonstrate msgsnd Program to test msgsnd 2 msgsnd k lt key gt i lt id gt t lt type gt b lt bytes gt c lt count gt n k lt key gt the key to use or i lt id gt the mq id t lt type gt th type of each message default 1 b lt bytes gt th c lt count gt th n us size of each message default 64 min 32 number of messages to send default 1 max 99999 e IPC_NOWAIT flag lt count gt messages of lt type gt lt bytes gt each on the queue Each message is an ASCII string containing the time and date and a serial number 1 lt count gt minimum message is 32 bytes ay include lt sys msg h gt msg queue stuff ipc h types h include lt unistd h gt for getopt include lt errno h gt errno and perror include lt time h gt time 2 and ctime_r 3 include lt stdio h gt int main int argc char argv key_t key key for msgget int msgid 1 specified or received msg queue id int msgflg 0 flag 0 or IPC_NOWAIT long type 1 message type 0 is not valid to msgsnd size_t bytes 64 message text size int count 1 number to send int c struct msgspace long type char text 32 msg while 1 c getopt argc argv k i t b c n switch c case k key strtoul optarg NULL 0 key key_t break
3. xy void resignArena usptr_t arena arenaStuff_t stuff arenaStuff_t usgetinfo arena ussetlock stuff gt updateLock stuff gt joinedProcs usunsetlock stuff gt updateLock It might seem that when the function resignArena in Example 3 4 finds that it has reduced the joinedProcs count to 0 it could deinitialize the arena for example unlinking the file on which the arena is based This is not a good idea because of the remote chance of the following sequence of events 1 Process A executes joinArena initializing the arena 2 Unrelated process B executes joinArena through the usinit call but is suspended for a higher priority process before executing usgetinfo 3 Process A detects some error unrelated to arena use and as part of termination calls resignArena 4 Process B resumes execution with the call to usgetinfo If the resignArena function did something irrevocable such as unlinking or truncating the arena file it would leave process B in an unexpected state System V Shared Memory Functions System V Shared Memory Functions The System V shared memory functions allow two or more processes to share memory Unlike the IRIX method in which the external name of a shared arena is also the name of a file the external name of an SVR4 shared segment is an integer held in an IPC name table see SVR4 IPC Name Space on page 50 The functions and commands used with SVR
4. This function takes a file descriptor and prints a report showing all locks currently set on that file The loop variable is the l_ustart field of the flock structure The function asks fcntl for the first lock that would block a lock from l_start to the end of the fil 1_len 0 When no lock would block such a lock the returned l_type contains F_UNLCK and the loop ends Otherwise the contending lock is displayed l_start is set to the end point of that lock and the loop repeats a void printAllLocksOn int fd struct flock Feki Find and print write lock blocked segments of file void printf sysid pid type start length n lck l_whence 0 lck l_start OL lck l_len OL for lck l_type 0 lck 1l_type F_UNLCK lck l_type F_WRLCK void fentl fd F_GETLK amp lck if lck l_type F_UNLCK void printf 5d 5d c 8d S8d n ick l_sysid lck 1l_pid lck 1l_type F_WRLCK W R lck l start lck l_len if lck l_len 0 break this lock goes to end of file stop lck l_start l1ck l_len fentl with the F_GETLK command always returns correctly that is it will not sleep or fail if the values passed to it as arguments are valid 188 Using Record Locking The lockf function with the F_LTEST command can also be used to test if there is a process blocking a lock This function does not however return the information about where
5. Describes two different facilities for creating and using message queues Chapter 2 Interprocess Communication The term interprocess communication IPC describes any method of coordinating the actions of multiple processes or sending data from one process to another IPC is commonly used to allow processes to coordinate the use of shared data objects for instance to let two programs update the same data in memory without interfering with each other or to make data acquired by one process available to others This chapter provides an overview of the IPC implementations available including e Types of Interprocess Communication Available on page 46 e Using POSIX IPC on page 48 e Using IRIX IPC on page 49 e Using System V IPC on page 49 e Using 4 2 BSD IPC on page 52 The following chapters in this Part provide details as follows e Chapter 3 Sharing Memory Between Processes covers shared memory e Chapter 4 Mutual Exclusion covers semaphores locks and similar facilities e Chapter 5 Signalling Events covers the different signal facilities e Chapter 6 Message Queues describes two varieties of message queue 45 Chapter 2 Interprocess Communication Types of Interprocess Communication Available IRIX is compatible with a broad variety of IPC mechanisms IRIX conforms to the POSIX standards for real time extensions IEEE standard 1003 1b and thre
6. Example Uses of semctl for Query 106 Example Uses of semop 108 Using the Examples 110 Contents 5 Signalling Events 113 Signals 113 Signal Numbers 114 Signal Implementations 116 Signal Blocking and Signal Masks 117 Multiple Signals 117 Signal Handling Policies 118 Default Handling 118 Ignoring Signals 118 Catching Signals 118 Synchronous Signal Handling 119 Signal Latency 119 Signals Under X Windows 120 POSIX Signal Facility 120 Signal Masking 122 Using Synchronous Handling 122 Using Asynchronous Handling 123 System V Signal Facility 124 BSD Signal Facility 126 Timer Facilities 127 Timed Pauses and Schedule Cession 127 Time Data Structures 128 Time Signal Latency 128 How Timers Are Managed 129 POSIX Timers 129 Getting Program Execution Time 130 Creating Timestamps 131 Using Interval Timers 133 BSD Timers 134 Hardware Cycle Counter 135 6 Message Queues 137 Overview of Message Queues 138 Implementation Differences 138 Contents Uses of Message Queues 140 POSIX Message Queues 140 Managing Message Queues 141 Creating a Message Queue 141 Opening an Existing Queue 142 Specifying Blocking or Nonblocking Access 142 Using Message Queues 143 Sending a Message 143 Receiving a Message 143 Using Asynchronous Notification 143 Example Programs 144 Example of mq_getattr 145 Example of mq_open 147 Example of mq_send 149 Example of mg_receive 152 System V Message Queues 155 Managing SVR4 Message Queues 155
7. if bsize gt dio d_maxiosz fprintf stderr bsize d too large n bsize return 4 else set a default alignment rule dio d_mem 8 Get a buffer aligned the way we need it ey buffer memalign dio d_mem bsize if buffer fprintf stderr could not allocate buffer n return 5 bzero buffer bsize Write the number of records requested as fast as we can xf for c 0 c lt nwrites c if bsize write ofd buffer bsize char msg 80 sprintf msg d th write d buffer d ct 1l ofd bsize perror msg break To level the playing field sync the file if not sync d already KY if 0 oflag amp O_DIRECT O_SYNC fdatasync ofd close ofd return 0 235 Chapter 9 High Performance File I O Using a Delayed System Buffer Flush When your application has both clearly defined times when all unplanned disk activity should be prevented and clearly defined times when disk activity can be tolerated you can use the syssgi function to control the kernel s automatic disk writes Prior to a critical section of length s seconds that must not be interrupted by unplanned disk writes use syssgi as follows syssgi SGI_BDFLUSHCNT S The kernel will not initiate any deferred disk writes for s seconds At the start of a period when disk activity can be tolerated initiate a flush of the kernel s buffe
8. return errno The following points should be noted about Example 7 3 e The type of lock is not specified because lockf only supports exclusive locks e The operation code F_TLOCK specifies that the function should return if the lock cannot be placed The F_LLOCK operation would request that the function suspend until the lock could be placed e The start of the record is set implicitly by the current file position That is why Iseek is called to ensure the correct file position before lockf is called Whole File Lock With flock Example 7 4 displays a third example of the lockWholeFile subroutine this one using flock Using Record Locking Example 7 4 Setting a Whole File Lock With flock define _BSD_COMPAT include lt sys file h gt includes fcentl h include lt errno h gt for EAGAIN define MAX_TRY 10 int lockWholeFile int fd int tries int limit tries tries MAX_TRY int try for try 0 try lt limit try if 0 flock fd LOCK_EX LOCK_NB break mission accomplished if errno EWOULDBLOCK break mission impossible sginap 1 let lock holder run return errno The following points should be noted about Example 7 4 e The compiler variable BSD_COMPAT is defined in order to get BSD compatible definitions from standard header files e The only use of flock is to lock an entire file so there is no attemp
9. styleWeWillUse is set which is what we were after IC Values There are several pieces of information an input method may require depending on the input context and style chosen by the application The input method can acquire any such information it needs from the input context ignoring any information that does not affect the style or IM A full description of every item of information available to the IM is supplied in X Window System Third Edition The following is a brief list XNClient Window Specifies to the IM which client window it can display data in or create child windows in Set once and cannot be changed XNFilterEvents An additional event mask for event selection on the client window XNFocusWindow The window to receive processed composed Key events XNGeometryCallback A geometry handler that is called if the client allows an IM to change the geometry of the window XNInputStyle Specifies the style for this IC 401 Chapter 16 Internationalizing Your Application 402 XNResourceClass XNResourceName XNStatusAttributes XNPreeditAttributes The resource class and name to use when the IM looks up resources that vary by IC The attributes to be used for any status and pre edit areas nested variable length lists Pre Edit and Status Attributes When an IM is going to provide state it needs some simple X information with which to do its work For example if an IM is going to draw status in
10. Mapping A process can ask IRIX to map associate byte for byte a segment of address space to one of a number of special objects for example the contents of a file This is covered further under Mapping Segments of Memory on page 12 Allocation The brk function extends the heap the segment devoted to data toa specific virtual address The malloc function allocates memory for use calling brk as required See the brk 2 malloc 3 and malloc 3x reference pages An address is defined by an entry in the page tables A defined address is always related to a backing store a source from which its contents can be refreshed A page in a text segment is related to the executable file A page of a data or stack segment is related to a page in a swap partition on disk The total size of the defined pages in an address space is its virtual size displayed by the ps command under the heading SZ see the ps 1 reference page Once addresses have been defined in the address space by allocation there is no way to undefine them except to terminate the process To free allocated memory makes the freed memory available for reuse within the process but the pages are still defined in the page tables and the swap space is still allocated Address Space Limits The segments of the address space have maximum sizes that are set as resource limits on the process Hard limits are set by these variables rlimit_umem_max Total size of the addre
11. Send a signal to a specified thread Examine or change the mask of signals allowed and blocked You must use pthread_sigmask in a program that is linked with libpthread Specify or query the signal handling policy for a specified signal Specify or query an alternate stack area to be used by a signal handler Return the set of signals pending for the calling process or thread Manipulate signal mask objects in memory Unblock selected signals for the calling process or thread and wait for a signal to be received asynchronously Wait for and receive specified signals in a synchronous manner In addition to the reference pages listed in Table 5 3 the following have important information about signal handling signal 5 siginfo 5 ucontext 5 Detailed overview of signals and signal handling Description of the information structure passed to a POSIX signal handler Description of machine context structure passed to a POSIX signal handler 121 Chapter 5 Signalling Events 122 Signal Masking Each process and thread has an active signal mask A single thread program sets or queries its signal mask using sigprocmask A multithreaded program any program that linked libpthread which provides the pthread version of the standard library should use pthread_sigmask Besides the active signal mask you may have other signal mask objects type sigset_t in memory The sigsetops 3 reference page documents a
12. There are three bands of nondegrading priorities designated by symbolic names declared in sys schedctl h e A real time band from NDPHIMAX to NDPHIMIN System daemons and real time programs run in this band which has higher priority than any interactive process e Anormal band from NDPNORMMAX to NDPNORMMIN These values have the same priority as interactive programs Processes at these priorities compete with interactive processes but their priorities do not degrade with time e Abatch band from NDPLOMAX to NDPLOMIN Processes at these priorities receive available CPU time and are scheduled from a batch queue Tip The IRIX priority numbers are inverted in the sense that numerically smaller values have superior priority For example NDPHIMAX is 30 and NDPHIMIN is 39 However as long as you declare priority values using symbolic expressions the numbers work out correctly For example the statement define NDPHIMIDDLE NDPHIMIN NDPHIMAX NDPHIMIN 2 produces a middle value of 35 as it should When you create a cooperating group of processes it is important that they all execute at the same time provided there are enough CPUs to handle all the members of the group that are ready to run This minimizes the time that members of the share group spend waiting for each other to release locks or semaphores Use schedctl to initiate gang scheduling for the share group IRIX attempts to schedule all processes to ex
13. This chapter covers the following major topics Overview of Mutual Exclusion on page 78 defines such terms as lock mutex semaphore and barrier POSIX Facilities for Mutual Exclusion on page 82 covers the POSIX functions for semaphores and mutexes TRIX Facilities for Mutual Exclusion on page 87 covers IRIX locks barriers and semaphores and the test and set facility Using Compiler Intrinsics for Test and Set on page 96 covers System V semaphores 77 Chapter 4 Mutual Exclusion Overview of Mutual Exclusion 78 IRIX offers five kinds of mutual exclusion each kind with its limits and advantages e Test and set instructions use special instructions in the MIPS CPU to update a memory location in a predictable way e The lock or mutex enables processes to enforce serial use of data or code e The condition variable lets a thread give up a lock and sleep until an event happens then reclaim the lock and continue all in a single operation e The semaphore lets independent processes manage a countable resource in an orderly way e The barrier lets processes coordinate their initialization There is a hierarchy of complexity Test and set instructions are a primitive facility that could be used to implement the others The lock is a simple object that could be used to implement semaphores and barriers The semaphore is the most flexible and general facility Test and Set Instructions T
14. When a program deals with internationalized input text it is important to extend regular expression facilities to cover internationalized strings and coded character sets It is difficult to write regular expressions that apply to more than one language or to languages with accented multi character collating elements because of limitations in syntax Application programs can use the wsregexp function library documented in the wsregexp 3W reference page to support internationalized regular expression behavior ANSI X3 159 198X Standard for C The American National Standards Committee X3J11 standard for the C programming language includes a number of library functions that are defined to operate internationally that is they modify their operation in a manner appropriate to the user s native language and cultural environment Locale Specific Behavior The X Open definition includes the international functions in Table 16 4 as defined in Draft ANSI X3 159 Programming Language C ANSI functions that are enhanced by the X Open definition are marked with an asterisk Table 16 4 ANSI Compatible Functions Function Function continued atof scanf fprintf setlocale fscanf sprintf isalnum sscanf isalpha strcoll isgraph sterror islower strftime isprint strtod ispunct strxfrm isspace tolower isupper toupper printf Draft ANSI X3 159 Programming Language C also
15. compress utopR10 pef But you could combine both steps simply as follows bdftopcf UTRG_10 bdf compress c gt utopR10 pcf Z 323 Chapter 15 Working With Fonts 4 324 Move the bitmap font files to the appropriate directory usr lib X11 fonts 100dpi or usr lib X11 fonts 75dpi You can of course combine this step with the format conversion step as follows bdftopcf UTRG_10 bdf compress c gt usr 1lib X11 fonts 100dpi utopR10 pcf Z You can tell the resolution for which a font was designed by the name of the directory in which the font designer stored the font files or by the information in the header of a bitmap font file In a BDF 2 1 font file the horizontal and vertical resolution are specified in the X font name They are also specified after the point size as the second and third numeric values in a SIZE entry For example the entry SIZE 8 100 100 within the file indicates an 8 point font that was designed for the horizontal and vertical resolution of 100 dpi For Type 1 PostScript font families there is one entry per font family in the file usr lib X11 fonts ps2xlfd_map For each Japanese font family shipped by Silicon Graphics there is an entry in the file usr lib X11 fonts ps2xIfd_map japanese When adding a new Type 1 font insert an entry in the appropriate file for each style variation in the font family It is not necessary to have an entry for each bitmap size For example the entries in ps
16. e Recode this part of the program to derive the maximum memory size in some more reasonable and portable way for instance from an environment variable or the size of an input file e Using setrlimit set a lower maximum for rlimit_data_max so that malloc returns NULL at a reasonable allocation size independent of the swap disk allocation see the getrlimit 2 reference page e Restore the conventional UNIX behavior for the whole system Use chkconfig to turn off the variable vswap and reboot see the chkconfig 1 reference page Note The function calloc touches all allocated pages in the course of filling them with zeros Hence memory allocated by calloc is defined as soon as it is allocated However you should not rely on this behavior It is possible to implement calloc in such a way that it like malloc does not define allocated pages until they are used This might be done in a future version of IRIX Page Validation Although an address is defined the corresponding page is not necessarily loaded in physical memory The sum of the defined address spaces of all processes is normally far larger than available real memory IRIX keeps selected pages in real memory A page that is not present in real memory is marked as invalid in the page tables When the program refers to an address on an invalid page the CPU traps to the kernel which supplies the page The contents of invalid pages can be supplied in one of t
17. permissions segment size POSIX Shared Memory Operations int oflags 0 open flags receives c x t int ropt 0 r option seen int wopt 0 w option seen int shm_fd file descriptor int mprot PROT_READ protection flags to mmap int mflags MAP_SHARED mmap flags void attach assigned memory adddress char path gt first non option argument Tat ce whil Co tA c getopt argc argv p s cxrtw switch c case p permissions perms int strtoul optarg NULL 0 break case s segment size size size_t strtoul optarg NULL 0 break case c use O_CREAT oflags O_CREAT break case x use O_EXCL oflags O_EXCL break case t use O_TRUNC oflags O_TRUNC break case r use O_RDONLY ropt 1 break case w wait after attaching wopt 1 break default unknown or missing argument return 1 switch while if optind lt argc path argv optind first non option argument else printf Segment pathname required n return 1 if 0 ropt read write access reflect in mprot and mflags oflags O_RDWR ay 59 Chapter 3 Sharing Memory Between Processes 60 else mprot PROT_WRITE mflags MAP_AUTOGROW MAP_AUTORESRV read only access mprot and mf
18. No access You can make pages inaccessible while retaining them as part of the address space Note The mprotect function changes the access rights only to the memory image of a mapped file You can apply it to the pages of a mapped file in order to control access to the file image in memory However mprotect does not affect the access rights to the file itself nor does it prevent other processes from opening and using the file as a file Synchronizing the Backing Store IRIX writes modified pages to the backing store as infrequently as possible in order to save time When pages are locked they are never written to backing store This does not matter when the pages are ordinary data When the pages represent a file mapped into memory you may want to force IRIX to write any modifications into the file This creates a checkpoint a known good file state from which the program could resume Using Origin2000 Nonuniform Memory The msync function see the msync 2 reference page asks IRIX to write a specified segment to backing store The segment must be a whole multiple of pages You can optionally request e synchronous writes so the call does not return until the disk I O is complete ensuring that the data has been written e page invalidation so that the memory pages are released and will have to be reloaded from backing store if they are referenced again Releasing Unneeded Pages Using the madvise function see the
19. There are three key differences between a thread and a process A UNIX process has its own set of UNIX state information for example its own effective user ID and set of open file descriptors Threads exist within a process and do not have distinct copies of these UNIX state values Threads share the single state belonging to their process Normally each UNIX process has a unique address space of memory segments that are accessible only to that process lightweight processes created with sproc share all or part of an address space Threads within a process always share the single address space belonging to their process Processes are scheduled by the IRIX kernel A change of process requires two context changes one to enter the kernel domain and one to return to the user domain of the next process The change from the context of one process to the context of another can entail many instructions In contrast threads are scheduled by code that operates largely in the user address space without kernel assistance Thread scheduling can be faster than process scheduling The POSIX standard for multithreaded programs is supported by IRIX 6 2 with patches 1361 1367 and 1389 installed and in all subsequent releases of IRIX In addition the Silicon Graphics implementation of the Ada95 language includes support for multitasking Ada programs using what are essentially threads although not implemented using the POSIX library For
20. XVaNestedList arglist XIC ic arglist XVaCreateNestedList 0 XNFontSet fontset XNForeground WhitePixel dpy screen XNBackground BlackPixel dpy screen NULL ic XCreateIC im XNInputStyle styleWeWillUse XNClientWindow window XNFocusWindow window XNStatusAttributes arglist XNPreeditAttributes arglist NULL XFree arglist if ic NULL exit_with_error Using the IC A multi window application may choose to use several input contexts But for simplicity assume that the application just wants to get to the internationalized input using one method in one window Using the IC is a matter of making sure you check events the IC wants and of setting IC focus If you are setting up a window for the first time you know the event mask you want and you can use it directly If you are attaching an IC to a previously configured window you should query the window and add in the new event mask 403 Chapter 16 Internationalizing Your Application Example 16 11 Using the IC unsigned long imEventMask XGetWindowAttributes dpy win amp winAtts XGetICValues ic XNFilterEvents amp imEventMask NULL imEventMask winAtts your_event_mask XSelectInput dpy window imEventMask XSetICFocus ic At this point the window is ready to be used Events Under IM Control Processing events under input method control is almost the same in X11R6 as it was under R4 an
21. bzero void array MAX_INFILES sizeof child_t Loop over the arguments setting up child structs and counting input files Quit if a file won t open or seek or if we can t get a buffer or semaphor for nfiles 0 argno l argno lt argc targno if 0 strcemp argv argno o is the o argument argno if argno lt argc ofName argv argno else fprintf stderr o must have a filename after n return 1 else if 0 stremp argv argno a is the a argument char c argv ttargno 0 switch c 214 Asynchronous I O Example case 0 method inProc0O break case 1 method inProcl break case 2 method inProc2 break case 3 method inProc3 break default fprintf stderr unknown method a c n c return 1 lse if argv argno 0 is unknown option fprintf stderr aiocat o outfile a 0 1 2 3 infiles n return 1 else neither o nor a assume input file if nfiles lt MAX_INFILES save the filenam E pc amp array nfiles strcpy pc gt fname argv argno allocate a buffer and a semaphore Not all child procs use the semaphore but so what Ef pc gt buffer usmalloc BLOCKSIZE arena QUITIFNULL pc gt buffer usmalloc buffer pc gt sema usnewsema arena 0 QUITIFNULL pc gt sema usnewsema
22. fprintf stderr m c n optarg return 1 break case b blocksize bsize strtol optarg NULL 0 break case n number of writes nwrites strtol optarg NULL break case i i info 1 break default return 1 end switch end while 0 233 Chapter 9 High Performance File I O Ensure a file path if ofile strcpy outpath ofile else tmpdir getenv TMPDIR if tmpdir tmpdir var tmp strcpy outpath tmpdir strcat outpath dirio out Open the file for output truncating or creating it AY oflag O_WRONLY O_CREAT O_TRUNC ofd open outpath oflag 0644 if 1 ofd char msg 256 sprintf msg open s 0x x 0644 outpath oflag perror msg return 1 If applicable m d get the DIOINFO for the file and display EA if oflag amp O_DIRECT void fentl ofd F_DIOINFO amp dio if info printf dioattr d_mem 8d 0x 08x n dio d_mem dio d_mem printf dioattr d_miniosz 8d 0x 08x n dio d_miniosz dio d_miniosz printf dioattr d_maxiosz 8d 0x 08x n dio d_maxiosz dio d_maxiosz if bsize lt dio d_miniosz fprintf stderr bsize d too small n bsize return 2 if bsize dio d_miniosz fprintf stderr bsize d is not a miniosz multiple n bsize 234 Using Direct I O return 3
23. isascii char argv System V Message Queues key for msgget specified or received msg queue id key_t key int msqid 1 J int msgflg 0 eo flag long type 0 F size_t bytes 64 fe int count 1 int quiet int c struct msgspace long type 0 0 IPC_NOWAIT message type message size limit number to receive quiet flag char text 321 MSG_NOERROR msg whil 1 1 c getopt argc argv k i t b c enq switch c case k key key key_t strtoul optarg NULL 0 break case i l id msqid int strtoul optarg NULL 0 break case t typ can be negative type strtol optarg NULL 0 break case b bytes no minimum bytes strtoul optarg ULL 0 break case c count no maximum count strtoul optarg ULL 0 break case n nowait msgflg IPC_NOWAIT break case e noerror allow truncation of msgs msgflg MSG_NOERROR break case q quiet quiet 1 break default unknown or missing argument return 1 171 Chapter 6 Message Queues if 1 msqid no id given try key msqid msgget key 0 msg struct msgspace calloc 1 sizeof long bytes if 1 msqid for c 1 c lt count c int ret msgrcv msqid msg bytes type msgflg if
24. MQ str gettxt 10 Hello world n 377 Chapter 16 Internationalizing Your Application 378 Using pfmt pfmt is one of the most important routines dealing with MNLS catalogs because it is used to produce most system diagnostic messages pfmt formats like printf and produces standard error message formats see the pfmt 3 reference page for the function or pfmt 1 for shell use It can usually be used in place of perror For example pfmt stderr MM_ERROR MQ 64 Permission denied would produce by default such as when the Mozambique locale is unavailable ERROR Permission denied The syntax of pfmt is include lt pfmt h gt int pfmt FILE stream long flags char format The flags are used to indicate severity type or control details to pfmt The format string includes information specifying which message from which catalog to look for Flag details are discussed in the following section The format is discussed in the Format Strings for pfmt on page 379 Labels Severity and Flags pfmt flags are composed of several groups specify no more than one from each group Specify multiple flags by using OR The groups are as follows output format control MM_NOSTD MM_STD catalog access control MM_NOGET MM_GET severity MM_HALT MM_ERROR MM_WARNING MM_INFO action message specification MM ACTION pfmt prints messages in the form Iabel severity text Severi
25. Resigning From an Arena 70 shmget System Call Example 73 shmat System Call Example 75 Dynamic Allocation of POSIX Unnamed Semaphore 83 Using Compare and Swap on a LIFO Queue 94 Program to Demonstrate semget 102 Program to Demonstrate semctl for Management 104 Program to Demonstrate semctl for Sampling 106 Program to Demonstrate semop 108 Example of POSIX Time Functions 131 Program to Demonstrate mq_getattr and mq_setattr 146 Program to Demonstrate mq_open 148 Program to Demonstrate mq_send 150 Program to Demonstrate mq_receive 153 Program to Demonstrate msgget 161 Program to Demonstrate msgctl 164 Program to Demonstrate msgsnd 167 Program to Demonstrate msgrcv 170 Opening a File for Locked Use 179 Setting a Whole File Lock With fentl 181 Setting a Whole File Lock With lockf 182 Setting a Whole File Lock With flock 183 XXV List of Examples xxvi Example 7 5 Example 7 6 Example 7 7 Example 7 8 Example 7 9 Example 8 1 Example 8 2 Example 8 3 Example 8 4 Example 9 1 Example 9 2 Example 12 1 Example 13 1 Example 13 2 Example 13 3 Example 16 1 Example 16 2 Example 16 3 Example 16 4 Example 16 5 Example 16 6 Example 16 7 Example 16 8 Example 16 9 Example 16 10 Example 16 11 Example 16 12 Example 16 13 Record Locking With Promotion Using fentl 184 Record Locking Using lockf 186 Detecting Contending Locks Using fentl 188 Testing for Contending Lock Using lo
26. Set up the aiocb for a read pab gt aio_fildes pch gt fd pab gt aio_offset pch gt inbase pab gt aio_nbytes BLOCKSIZE queue it SA_SIGINFO sigHandler2 parent will shut down ASAP ey and wait for it if ret aio_read pab ret inWait2 pch if ret break could not start read or it ended badly get the result of the read call the count of bytes read Since aio_error returned 0 the count is nonnegative It could be 0 or less than BLOCKSIZE indicating EOF bytes aio_return pab actual read result if bytes break no need to write a last block of 0 pch gt inbase bytes where to read next time Set up the aiocb for a write queue it and wait for it x pab gt aio_fildes outFD pab gt aio_nbytes bytes pab gt aio_offset pch gt outbase if ret aio_write pab ret inWait2 pch if ret break 225 Chapter 8 Using Asynchronous I O pch gt outbase bytes where to write next time while ret amp amp bytes BLOCKSIZE The loop is complete If no errors so far use aio_fsync to ensure that output is complete This requires waiting yet again xy if ret if ret aio_fsync O_SYNC pab ret inWait2 pch Flag any errors for the parent proc If none count elapsed time rd if ret terrors lse pch gt etime clock
27. We have a valid status Check that switch status case XLookupKeysym DealWithKeysym keysym break case XLookupBoth DealWithKeysym keysym FALL INTO charcter case case XLookupChars DealWithString buf buflength case XLookupNone break end switch status nd case KeyPress segment break we are in a switch event type statement GUI Concerns GUI Concerns It shouldn t be significantly more difficult to internationalize an application with a graphical user interface than an application without such an interface but there are a few further issues that must be addressed e X Resources for Strings on page 407 covers labeling objects using X resources e Layout on page 408 describes creating layouts that are usable after localization e Icons on page 409 explains some concerns for localizing icons X Resources for Strings Resource lookup mechanisms in Xlib as well as in toolkits monitor locale environment variables when locating resource files For string constants that are used within toolkit objects resources provide a simpler solution than do message catalogs These are some common objects that should definitely get their text from resources e Labels e Buttons e Menu items e Dialog notices and questions Any object that employs some sort of text label should be labeled via resources Since the localizer wants to provide strings for the lo
28. amp lck lt 0 return 1 Lock this with write lock lck l_ustart this if fcntl fd F_SETLKW amp lck lt 0 Failed to lock this return here to read lock lck l_type F_RDLCK lck l_start here void fentl fd F_SETLKW amp lck return 1 Promote lock on next to write lock lck l_start next if fcntl fd F_SETLKW amp lck lt 0 Failed to promote next return here to read lock lck l_type F_RDLCK lck l_start here void fentl fd F_SETLK amp lck and remove lock on this lck l_type F_UNLCK lck l_start this void fentl fd F_SETLK amp lck return 1 return this Example 7 5 uses the FSSETLKW command to fentl with the result that the calling process will sleep if there are conflicting locks at any of the three points If the F_LSETLK command was used instead the fentl system calls would fail if blocked The program would then have to be changed to handle the blocked condition in each of the error return sections as in Example 7 2 185 Chapter 7 File and Record Locking 186 It is possible to unlock or change the type of lock on a subsection of a previously set lock this may cause an additional lock two locks for one system call to be used by the operating system This occurs if the subsection is from the middle of the previously set lock Example 7 6 shows a similar ex
29. b bytes Maximum size of a message for example b 0x200 n Use the IPC_NOWAIT flag with msgrev e Use the MSG_NOERROR flag with msgrcv to truncate messages longer than bytes q Be quiet do not display the received message Use for performance testing As each message is received it is displayed A sequence number and the message type are always displayed the first 32 bytes of the text are displayed if it begins with ASCII 169 Chapter 6 Message Queues 170 Example 6 8 ar include include include include include int main int argc Program to Demonstrate msgrcv Program to test msgrcv 2 lt sys msg h gt lt unistd h gt lt errno h gt lt ctype h gt lt stdio h gt msgrcv k lt key gt i lt id gt t lt type gt b lt bytes gt c lt count gt n e q k lt key gt the key to use or i lt id gt the mq id t lt type gt the type of message default 0 any msg b lt bytes gt the max size to receive default 64 c lt count gt the number of messages to receive default 1 f use IPC_NOWAIT flag e use MSG_NOERROR flag truncate long msg q quiet do not display received messag The program calls msgrcv lt count gt times or until an error occurs each time requesting a message of type lt type gt and max size lt bytes gt msg queue stuff ipc h types h for getopt errno and perror
30. e However if you map a large file and then try to lock memory the attempt to lock could fail because there is not enough physical memory to hold the entire address space including the mapped file One alternative is to map an entire file perhaps hundreds of megabytes into the address space but to lock only the portion or portions that are of interest at any moment For example a visual simulator could lock the parts of a scenery file that the simulated vehicle is approaching When the vehicle moves away from a segment of scenery the simulator could unlock those parts of the file and possibly use madvise to release them see Releasing Unneeded Pages on page 29 Additional Memory Features Unlocking Memory The function summarized in Table 1 3 are used to unlock memory Table 1 3 Functions for Unlocking Memory Function Name Compatibility Purpose and Operation munlock 3C POSIX Unlock a specified range of locked addresses mlockall 3C POSIX Unlock the entire address space of the calling process munpin 3C IRIX Unlock a specified range of addresses punlock SVR4 Unlock addresses locked by plock You should avoid mixing function families for example if you lock memory with the POSIX function mlock do not unlock the memory using munpin The mpin function maintains a counter for each locked page showing how many times it has been locked You must call munpin the same number of times before the pag
31. is the ID number of the segment It is used to identify the segment to other functions Attaching a Shared Segment The shmget function creates the segment or verifies that it exists but does not actually make it a part of the process address space That remains to be done with a call to shmat attach passing the identifier returned by shmget You can pass a desired base address to shmat or you can pass NULL to have the system select the base address It is best to let the system choose the base this ensures that all processes have the same base address for the segment A process can detach a segment from its address space by calling shmdt Managing a Shared Segment The shmctl function gives you the ability to get information about a segment or to modify its attributes These operations are summarized in Table 3 7 Table 3 7 SVR4 Shared Segment Management Operations Keyword Operation Can Be Used By IPC_STAT Get information about the segment Any process having read access IPC_SET Set owner UID owner GID or access Creator UID owner UID or permissions superuser IPC_RMID Remove the segment from the IPC Creator UID owner UID or name space superuser SHM_LOCK Lock the segment pages in memory Superuser process only SHM_UNLOCK Unlock a locked segment Superuser process only System V Shared Memory Functions Information About Shared Memory The information structure returned by shmctl
32. lower any lower case letter 367 Chapter 16 Internationalizing Your Application 368 Cultural Data The items of cultural data listed in Table 16 9 are defined in the C locale Table 16 9 Cultural Data Names Categories and Settings Item Category Setting for the C Locale D_T_FMT LC_TIME a Yob Yor H M S Y D_FMT LC_TIME Yom d oy T_FMT LC_TIME H M S AM_STR LC_TIME AM PM_STR LC_TIME PM DAY_1 LC_TIME Sunday DAY_2 LC_TIME Monday DAY_3 LC_TIME Tuesday DAY _4 LC_TIME Wednesday DAY_5 LC_TIME Thursday DAY_6 LC_TIME Friday DAY_7 LC_TIME Saturday ABDAY_1 LC_TIME Sun ABDAY_2 LC_TIME Mon ABDAY_3 LC_TIME Tue ABDAY_4 LC_TIME Wed ABDAY_5 LC_TIME Thu ABDAY_6 LC_TIME Fri ABDAY_7 LC_TIME Sat MON_1 LC_TIME January MON_2 LC_TIME February Locale Specific Behavior Table 16 9 Cultural Data Names Categories and Settings continued Item Category Setting for the C Locale MON_3 LC_TIME March MON_4 LC_TIME April MON_5 LC_TIME May MON_6 LC_TIME June MON_7 LC_TIME July MON_8 LC_TIME August MON_9 LC_TIME September MON_10 LC_TIME October MON_11 LC_TIME November MON_12 LC_TIME December ABMON_1 LC_TIME Jan ABMON_2 LC_TIME Feb ABMON_3 LC_TIME Mar ABMON_4 LC_TIME Apr ABMON_5 LC_TIME May ABMON_6 LC_TIME Jun ABMON_7 LC_TIME Jul ABMON_8 LC_TIME Aug ABMON_9 LC_TIME Sep ABMON_10 LC_TIME Oct ABMON_11 LC_
33. new old gt next while 0O uscas lifo ptrdiff_t old ptrdiff_t new u return old include lt stdio h gt main usptr_t arena usinit var tmp cas arena item_t lifo NULL item_t tl t2 item_t pl p2 IRIX Facilities for Mutual Exclusion push_item amp lifo amp tl push_item amp lifo amp t2 p2 pull_item amp lifo pl pull_item amp lifo printf Sx printf Sx x n Sx n arena arena arena arena amp tl amp t2 r jes p1 p2 In Example 4 2 the push_item function pushes an item_t onto a LIFO queue and pull_item removes and returns the first item_t from a queue Both use uscas to update the queue anchor The main function contains a unit test of the functions first pushing two items then pulling them off finally displaying the addresses to verify that what was pushed could be pulled Using Compiler Intrinsics for Test and Set The MIPSpro C and C compilers version 7 0 introduce the intrinsic functions summarized in Table 4 10 Table 4 10 Compiler Intrinsics for Atomic Operations Intrinsic Prototype _ _op_and_fetch p v _ _fetch_and_op p v _ _lock_test_and_set p v _ _lock_release p ___compare_and_swap p w v _ _synchronize Purpose Barrier Atomically execute p op v p The op canbe Full add sub or and xor and nand Atomically execute t p p op
34. open the file as pc gt fd open pc gt fname O_RDONLY QUITIFMONE pc gt fd open get the size of the fil This leaves the fil positioned at end but there is no need to reposition NOTE is a valid and interesting test I I because all aio_read calls have an implied lseek 1 there is no check for zero length file Ix that case 215 Chapter 8 Using Asynchronous I O 216 xy pce gt fsize lseek pc gt fd 0 SEEK_END QUITIFMONE pc gt fsize lseek set the starting base address of this input file in the output file The first file starts at 0 Each one after starts at prior base prior size l EJ f nfiles not first pc gt outbase array nfiles 1 fsize array nfiles 1 outbase nfiles else printf Too many files s ignored n argv argno end for argce If there was no o argument construct an output file name Kof if ofName strcpy outPath tmpdir strcat outPath aiocat out ofName outPath Open creating or truncating the output file Do not use O_APPEND which would constrain aio to doing operations in sequence outFD open ofName O_WRONLY O_CREAT O_TRUNC 0666 QUITIFMONE outFD open output If there were no input files just quit leaving empty output ef if nfiles return 0 Note the nu
35. ret 67 Chapter 3 Sharing Memory Between Processes 68 if stuff arenaStuff_t usgetinfo arena Another process has created the arena and either has initialized it or is initializing it right now Acquire the lock which will block us until initializing is done Ef ussetlock stuff gt updateLock here do anything needing exclusive use of arena stuff gt joinedProcs another process has joined usunsetlock stuff gt updateLock release arena ret 1 end the loop else This process appears to be first to call usinit Allocate an arenaStuff structure with its updateLock already held and 1 process joined and try to swap it into place as the active one W xpect no errors in setting up arenaStuff If one occurs the arena is simply unusable and we return a NULL to the caller Kf if stuff usmalloc sizeof arenaStuff_t arena return stuff should never occur if stuff gt updateLock usnewlock arena return usptr_t 0 should never occur if uscsetlock stuff gt updateLock 1 return usptr_t 0 should never occur stuff gt joinedProcs 1 if ret uscasinfo arena 0 stuff Our arenaStuff is now installed Initialize it We hold the lock in arenaStuff as setUpArena expects The loop ends because ret is now nonzero setUpArena arena stuff usunsetlock stuff gt updateLock
36. their image of the file will be consistent But when two or more processes in different systems map the same NFS mounted file there is no way to coordinate their updates and the file can be corrupted File Integrity Any change to a file is immediately visible in the mapped segment This is always true when flags contains MAP_SHARED and initially true when flags contains MAP_PRIVATE A change to the file can be made by another process that has mapped the same file A mapped file can also be changed by a process that opens the file for output and then applies either write to update the file or ftruncate to shorten it see the write 2 and ftruncate 3 reference pages In particular if any process truncates a mapped file an attempt to access a mapped memory page that corresponds to a now deleted portion of the file causes a bus error signal SIGBUS to be sent When MAP_PRIVATE is specified a private copy of a page of memory is created whenever the process stores into the page copy on write This prevents the change from being seen by any other process that uses or maps the same file and it protects the process from detecting any change made to that page by another process However this applies only to pages that have been written into Frequently you cannot use MAP_PRIVATE because it is important to see data changes and to share them with other processes that map the same file However it is also important to prevent an unrelated
37. to query and set priorities These commands and functions use priority numbers ranging from 20 through 0 to 20 with lower arithmetic values having superior access to the CPU Only the IRIX schedctl function gives you complete access to a variety of operations related to process scheduling Some of the key operations are as follows NDPRI Set a nondegrading priority for the calling process see text GETNDPRI Query the nondegrading priority of the calling process SETMASTER Set the master process of a share group By default the parent process is the master process but it can transfer that honor SCHEDMODE SGS_SINGLE Cause all processes in the share group to be suspended except the master process set with SETMASTER Using Multiple Processes SCHEDMODE SGS_GANG Cause all processes in the share group to be scheduled as a gang with all running concurrently SCHEDMODE SGS_FREE Schedule the share group in the default fashion A program started interactively inherits a scheduling discipline based on degrading priorities That is the longer the process executes without voluntarily suspending the lower its dispatching priority becomes This strategy keeps a runaway process from monopolizing the hardware However you may have a CPU intensive application that needs a predictable execution rate This is the purpose of nondegrading priorities set with schedctl NDPRIJ or with the npri command see the npri 1 reference page
38. vals 1 1 0 0 nent 0 0 0 0 zent 1 0 0 0 Semaphore 0 is decremented and semsnap reveals that there is no longer a process waiting for zero in that semaphore but that now a process is waiting for semaphore 2 to be incremented semop i 130 p 0 semsnap i 130 vals 0 1 0 0 nents 206 0 oly 30 zent O 0 0 O 111 Chapter 4 Mutual Exclusion 112 Semaphore 2 is incremented and now there are no processes waiting semop i 130 v 2 semsnap i 130 vals 0 0 0 0 nents 10 0 0 0 zente lt 0 0 0 0 Another process is put in the background waiting on semaphore 0 Then the semaphore set is removed with ipcrm The waiting instance of semop ends displaying the error code from semop semop i 130 p 0 amp 9962 iperm s 130 semop Identifier removed Chapter 5 Signals Signalling Events Processes can receive signals in order to respond to asynchronous requests from software or to unexpected hardware events There are three different programming interfaces for receiving signals you must select one and use it consistently throughout a program Many programs need access to time data for one of two purposes to produce timestamps so that data can be ordered by its time of origin and to define intervals so the program can take action at regular times Intervals are presented to the program as signals These two issues are covered in the following topics e Signals on p
39. Creating a Message Queue 155 Accessing an Existing Queue 156 Modifying a Message Queue 156 Removing a Message Queue 156 Using SVR4 Message Queues 157 Sending a Message 157 Receiving a Message 157 Example Programs 158 Example of msgget 160 Example of msgctl 163 Example of msgsnd 166 Example of msgrcv 169 xi Contents 7 File and Record Locking 175 Overview of File and Record Locking 176 Terminology 176 Record 176 Read Shared Lock 177 Write Exclusive Lock 177 Advisory Locking 177 Mandatory Locking 177 Lock Promotion and Demotion 178 Controlling File Access With File Permissions 178 Using Record Locking 179 Opening a File for Record Locking 179 Setting a File Lock 180 Whole File Lock With fentl 181 Whole File Lock With lockf 182 Whole File Lock With flock 182 Setting and Removing Record Locks 183 Getting Lock Information 187 Deadlock Handling 190 Enforcing Mandatory Locking 190 xii Contents 8 Record Locking Across Multiple Systems 192 NFS File Locking 192 Configuring NFS Locking 193 Performance Impact 193 Using Asynchronous I O 195 About Synchronous and Asynchronous I O 195 About Synchronous Input 195 About Synchronous Output 196 About Asynchronous I O 196 Asynchronous I O Functions 197 Asynchronous I O Control Block 198 Initializing Asynchronous I O 198 Implicit Initialization 198 Initializing with aio_sgi_init 199 When to Initialize 200 Scheduling Asynchronous I O 200 Assuring Data Integrit
40. Hebrew see ISO 8859 8 specification Danish Dutch English Finnish French German Irish Italian Norwegian Portuguese Spanish Swedish Turkish Popular Encodings IRIX contains over 500 Latin 1 fonts as well as a few fonts for each of the other 8859 encoded character sets except 8859 6 and 8859 8 Currently IRIX contains no fonts for use with the 8859 6 or 8859 8 character sets To get the list of ISO 8859 fonts enter the following xlsfonts Or you can restrict the amount of output for example by typing xlsfonts 8859 2 To see the encoding use the xfd command For example xfd fn sgi screen medium r normal 9 90 72 72 m 60 is08859 1 For more information on x sfonts and xfd and installing and using fonts refer to Chapter 15 Working With Fonts Asian Languages Asian languages are commonly ideographic and employ large numbers of characters for their representation For example Japanese and Korean can be practically encoded in 16 bits Daily use Chinese can be also but archives and scholars frequently need more so Chinese is often encoded with up to four bytes per character 411 Chapter 16 Internationalizing Your Application 412 Some Standards Various Asian character sets have been developed some of which are considered standard Encodings for these sets are less standardized Asian character sets usually require larger than byte character types like those describe
41. MIPSpro Fortran 77 Refer to http www apri com for more information Creating Parallel Programs In each of the three languages the language compiler supports explicit statements that command parallel execution pragma lines for C directives and assertions for Fortran However placing these statements can be a demanding error prone task It is easy to create a suboptimal program or worse a program that is incorrect in subtle ways Furthermore small changes in program logic can invalidate parallel directives in ways that are hard to foresee so it is difficult to modify a program that has been manually made parallel For each language there is a source level program analyzer that is sold as a separate product IRIS POWER C MIPSpro Power Fortran 77 MIPSpro Power Fortran 90 The analyzer identifies sections of the program that can safely be executed in parallel and automatically inserts the parallelizing directives After any logic change you can run the analysis again so that maintenance is easier The source analyzer makes conservative assumptions about the way the program uses data As a result it often is unable to find all the potential parallelism However the analyzer produces a detailed listing of the program source showing each segment that could or could not be parallelized and why Directed by this listing you insert source assertions that give the analyzer more information about the program The method of creating
42. That way your entries do not disappear when you upgrade your system software Adding Font and Font Metric Files When you purchase a font or obtain a font that is in the public domain you need to add that font to your system and possibly to your printer in order to use it Adobe Systems donated bitmap outline and font metric files for the Utopia font family to the X Consortium This section shows how the font and font metric files for Utopia Regular were added to the IRIX operating system Other font and font metric files can be added in a similar way You need superuser privilege to make changes to X font directories Before you make any changes to any IRIX directory make a copy of its contents so that you can restore that directory if anything goes wrong For example your font files may not be in the right format and they may interfere with the access of Silicon Graphics font files Keep a log of the changes you make and mention those changes when you report a problem with font files to Silicon Graphics otherwise it may be very difficult or impossible for other people to reproduce any problems that you might report Adding a Bitmap Font The procedure in this section shows how to add Utopia Regular bitmap fonts to IRIX Other fonts can be added in a similar way Installing and Adding Font and Font Metric Files To add the Utopia bitmap fonts to the system follow these steps 1 2 Log in as root Choose names for the i
43. Whenever another process or thread needs a unit of work of that type it sends the unit to that queue as a message Another use of a message queue is to regulate the use of a scarce resource such as the buffers in a pool of buffers Each resource unit is represented by a message In order to obtain a unit you receive one message from the queue To release a unit for other processes to use you send the unit message back to the queue The latter scheme can be used to compensate for a performance problem The speed of communication through a queue is limited by the fact that every message is copied twice when a message is sent it is copied from the sender s buffer to some reserved memory space when the message is received it is copied into the buffer supplied by the receiving process or thread When messages are small or few in number copying is not a serious problem When messages are large copying can be avoided as follows Allocate a pool of message buffers Set up a queue of small messages each message representing a ticket to use a particular buffer In order to obtain a buffer a process receives a message from this queue The process fills the buffer then it sends the buffer without copying by sending only the ticket on another message queue The process that receives the ticket uses the data in the buffer without needing to copy it and releases the buffer by sending the ticket to the original queue P
44. and release it with pthread_rwlock_unlock A read lock is acquired by calling pthread_rwlock_rdlock and released with pthread_rwlock_unlock When a thread must not be blocked it can use pthread_rwlock_trywrlock or pthread_rwlock_tryrdlock to test the lock and apply it only if it is available 299 Chapter 14 Message Passing Parallelism Ina message passing model your parallel application consists of multiple independent processes each with its own address space Each process shares data and coordinates with the others by passing messages using a formal interface The formal interface makes the program independent of the medium over which the message go The processes of the program can be in a single computer with messages moving via memory to memory copy but it is possible to distribute the program in different machines with messages passing over a network The Message Passing Toolkit package supports three libraries on which you can build a message passing application The Cray Shared Memory SHMEM library supports message passing in a single system Message Passing Interface MPI and Parallel Virtual Machine PVM models support distribution High level overviews of these are given under Message Passing Models on page 251 301 Chapter 14 Message Passing Parallelism Choosing a Message Passing Model 302 There are five considerations in choosing among the three message passing models compatibil
45. different sizes or both 311 Chapter 15 Working With Fonts 312 How Resolution Affects Font Size The images on most output devices such as laser printers and video monitors are created by coloring a rectangular array of small dots or pixels picture elements The number of dots or pixels that can be drawn per unit of length in a horizontal direction is called the horizontal resolution while the number of pixels that can be drawn per unit of length in a vertical direction is called the vertical resolution The most commonly used unit of measure for resolution is the number of dots per inch dpi Resolution is a device dependent unit of measure To display the resolution of your video monitor enter this command xdpyinfo grep resol You should get a response similar to this resolution 93x93 dots per inch The first number is the horizontal resolution the second the vertical resolution If you draw a single character at a given resolution the bounding box of the character is the smallest rectangle that enclose that character If you display all of the characters in a font in the same place without advancing you get a composite image of those characters If you then draw the smallest rectangle that encloses that composite image you have the bounding box for the font The size of a font is usually measured in the vertical direction That size is usually not smaller than the height of the font bounding box but it can
46. interrupt validity fault 10 IPC arenas 49 BSD style 46 IRIX arenas 49 IRIX style 46 49 parallel programming 49 portability 47 POSIX style 46 48 SVR4 style 46 types 47 423 Index Iran country code 416 Ireland country code 416 IRIX and IPC 46 ISO 3166 Country Codes 415 418 Israel country code 416 Italy country code 416 J Japan country code 416 K Kenya country code 416 kernel address space limits in 6 kernel address space 3 Korea country code 416 L 110n See localization languages ISO See internationalization encodings languages Latin See internationalization encodings Laos country code 417 latency of signal 119 latency of time signal 128 LC_ALL 341 LC_COLLATE 341 LC_CTYPE 341 LC_MESSAGES 341 LC_MONETARY 341 LC_NUMERIC 341 LC_TIME 341 424 LEGEND 380 lightweight process and mapped segments 15 limits command 6 lio_listioQ 201 Load Linked instruction 78 locale Motif 390 locales 340 346 categories 341 C locale value 344 collation 355 cultural data 368 data location 343 date formats 357 368 defined 335 empty strings 342 encoding 344 languages 343 location of data 343 modifiers 344 monetary formats 355 naming conventions 343 nonempty strings 343 numerical formats 355 setlocale 340 setting current 340 sorting rules 354 territories 343 time formats 357 locale specific behavior date 368 t
47. pch gt etime if DO_SPROCS Rendezvous with the rest of the family then quit E barrier convene nprocs endif end inProc2 BRK KK KR KR RR RRR RR RAR RR RA RA AA A A A A A A A A A A A A I inProc3 uses a callback and a semaphore It waits with a P operation The callback function executes a V operation This may come before or after the P operation Ay void callBack3 union sigval usv The callback function receives the pointer to the child_t struct as prepared in aio_sigevent sigev_value sival_ptr Use this to post the semaphore in the child_t struct Aap child_t pch usv sival_ptr usvsema pch gt sema return int inWait3 child_t pch 226 Asynchronous I O Example Suspend if necessary by polling the semaphore The callback function might b ntered before we reach this point or after Kp uspsema pch gt sema Return the status of the aio operation associated with the sema E return aio_error amp pch gt acb void inProc3 void arg size_t stk child_t pch arg starting arg is gt child_t for my file aiocb_t pab amp pch gt acb base address of the aiocb_t in child t int ret as long as this is 0 all is ok int bytes bytes read on each input Initialize request a callback in aio_sigevent The address of the child_t struct is passed as the siginf
48. persist until the system is rebooted or until they are removed manually Using System V IPC You can list all the components of the IPC name space using the ipcs command You can remove an object with the ipcrm command If you remove an object that is in use unpredictable results will follow Access Permissions IPC objects are not part of any filesystem but access to IPC objects is controlled by rules like the rules that govern file access For example if the access permissions of a shared memory segment are set to 640 the segment can be read write for processes that have the same UID as the segment owner but the segment is read only to processes that have only the GID of the owner and is inaccessible to other processes Choosing and Communicating Key Values The name of an IPC object is an integer Two small problems are how a program can select a unique key to use when making an IPC object and how to communicate the key to all the processes that need access to the object The ftok library function can be used to create a predictable key based on a file pathname For example unrelated but cooperating programs can agree to use ftok with a designated project file and project code so that each program will arrive at the same key Using ID Numbers When an IPC object is created it has the key it is given by the creating process but it is also assigned a second integer the ID The key number is chosen by the applicatio
49. process and causes more overhead in common group related operations Other differences are found in the design details of the two interfaces MPI for example supports asynchronous and multiple message traffic so that a process can wait for any of a list of message receive calls to complete and can initiate concurrent sending and receiving MPI provides for a context qualifier as part of the envelope of each message This permits you to build encapsulated libraries that exchange data independently of the data exchanged by the client modules MPI also provides several elegant data exchange functions for use by a program that is emulating an SPMD parallel architecture PVM is possibly more suitable for distributing a program across a heterogeneous network that includes both uniprocessors and multiprocessors and includes computers from multiple vendors When the application runs in the environment of a Silicon Graphics Array system MPI is the recommended interface 303 Chapter 14 Message Passing Parallelism 304 Differences Between PVM and MPI This section discusses the main differences between PVM and MPI from the programmer s perspective focusing mainly on PVM functions that are not available in MPI Although to a large extent the library calls of MPI and PVM provide similar functionality some PVM calls do not have a counterpart in MPI and vice versa Additionally the semantics of some of the equivalent calls ar
50. ret struct mq_attr obuf output of mq_getattr mq_msgsize whil 1 J c getopt argc argv c nq switch c case c count count strtoul optarg NULL 0 break case q quiet quiet 1 break case n nonblock oflags O_NONBLOCK break default unknown or missing argument return 1 153 Chapter 6 Message Queues 154 if optind lt argc path argv optind first non option argument else printf Queue pathname required n return 1 mqd mq_open path oflags if 1 mqd if mq_getattr mqd amp obuf get max message size msgptr calloc 1 obuf mq msgsize for c 1 c lt count c ret mq receive mqd msgptr obuf mq_msgsize amp msg_prio if ret gt 0 got a message if quiet if isascii msgptr printf d priority ld len d text 32 32s n c msg_prio ret msgptr else printf d priority ld len d nonascii n c msg_prio ret else an error on receive stop perror mq_receive break for c lt count if getattr else perror mq_getattr return 1 if open else perror mq_open O_WRONLY System V Message Queues System V Message Queues IRIX contains an implementation of message queues compatible with UNIX System V Release 4 SVR4 These message queue functions are demonst
51. shared memory semaphores mutexes condition variables and message queues The implementation is highly tuned and has low system overhead POSIX facilities are usable from POSIX threads see Chapter 13 Thread Level Parallelism IRIX unique library calls are provided for shared memory semaphores locks and barriers The implementation has slightly more overhead than POSIX operations but sometimes takes advantage of concurrent hardware in multiprocessors and has a number of special features such as the ability to apply poll to semaphores System function calls compatible with AT amp T System V Release 4 are provided for signal handling shared memory semaphores message queues and file locking The implementation is provided for ease of porting software but is not particularly efficient Library functions compatible with BSD UNIX are provided for signal handling file locking and socket support Select your IPC mechanisms based on these guidelines Never mix the implementations of a given mechanism in a single program For example unpredictable results can follow when a single program mixes POSIX and System V signal handling functions or mixes both BSD and System V file locking calls The POSIX libraries are the newest implementations and in many cases they are the most efficient A program based on POSIX threads should use POSIX synchronization mechanisms because they are optimized for pthreads use Use System V
52. system file permissions e Advisory locking is more efficient because a record lock check does not have to be performed for every I O request Record Locking Across Multiple Systems 192 Record locking is always effective within a single copy of the IRIX kernel Locking is effective within a multiprocessor because processes running in different CPUs of the multiprocessor share a single copy of the IRIX kernel Record locking can be effective on processes that execute in different systems that access a filesystem mounted through NFS However there are these drawbacks e Deadlock detection is not possible between processes in different systems e You must make sure that the NFS locking daemon is running in both the NFS client application and server systems e Using record locking on NFS files has a strong impact on performance NFS File Locking When a process running in an NFS client system requests a file or record lock a complex sequence of events begins For details consult the lockd 1M reference page First the kernel in the client system receives the lock request and determines that the file resides on a filesystem mounted using NFS The kernel sends the lock request to a daemon called rpc lockd This daemon is responsible for communicating lock requests to other systems Record Locking Across Multiple Systems The rpc lockd process sends the lock request to the rpc lockd daemon running on the NFS server where the t
53. 18 G Germany country code 416 getpagesize 5 getrlimit 6 421 Index Ghostscript 319 325 327 328 GRIO See guaranteed rate I O guaranteed rate I O 236 240 creating a real time file 238 requesting a guarantee 239 H hardware timer 135 heap segment 4 6 Hong Kong country code 416 i18n See internationalization input methods See internationalization input methods internationalization 333 413 ANSI compatible functions 361 character classification 357 character classification tables 363 character expressions 366 character sets and X 384 defined 346 codesets ASCII 347 349 defined 346 collating sequence tables 363 composing characters 393 configuration data 362 ctype 357 cultural data 368 customs 360 date formats 357 defined 335 eight bit cleanliness 347 encodings 422 about 344 and filesystem 346 Asian languages 411 defined 346 EUC 412 European languages 410 ISO 10646 413 ISO 8859 410 Latin 1 410 multibyte 348 Unicode 413 wehar 348 352 file I O 353 file typing rules 380 fimtmsg 379 GL input 392 GUIs 407 409 composition 408 editres 409 icons 409 layout 408 localized layout 409 object labels 407 text labels 407 icons 409 initializing Xlib 385 input contexts 400 404 creating 403 styles 400 using 403 values 401 input methods 395 406 about 391 event handling 404 Off the Spot style 398 On the Spot style 399
54. 4 1 allocates and initializes an unnamed semaphore and returns its address It returns NULL if there is a failure of either malloc or sem_init Example 4 1 Dynamic Allocation of POSIX Unnamed Semaphore sem_t allocUnnSem unsigned initVal sem_t psem sem_t malloc sizeof sem_t if psem malloc worked if sem_init psem 0 initVal free psem psem NULL return psem The function in Example 4 1 passes the second argument of sem_init pshared as 0 meaning the semaphore can only be used within the current process A semaphore of this kind can be used to coordinate pthreads in a threaded program 83 Chapter 4 Mutual Exclusion 84 If you want to use a semaphore to coordinate between IRIX processes with separate address spaces you must create the semaphore with a nonzero pshared and place the semaphore in a memory segment that is shared among all processes This feature is fully supported However you should specify pshared as 0 when possible because nonshared semaphores have higher performance Managing Named Semaphores A named semaphore is named in the filesystem so it can be opened by any process subject to access permissions even when the process does not share address space with the creator of the semaphore The functions used to create and manage named semaphores are summarized in Table 4 2 Table 4 2 POSIX Functions to Manage Named Semaphores Function Name Purpose a
55. 4th argument C7 om c getopt argc argv k i switch c case k key key key_t strtoul optarg NULL 0 break case i semid semid int strtoul optarg NULL 0 break default unknown or missing argument return 1 1 semid i not given must have k semid semget key 0 0 1 semid arg4 buf amp ds if 0 semctl semid 0 IPC_STAT arg4 nsems ds sem_nsems arg4 array semvals semctl semid 0 GETALL arg4 for j 0 j lt nsems j semns j semct1 semid j GETNCNT semzs j semct1 semid j GETZCNT printi varsi for j 0 j lt nsems j printf 2d semvals j Printf nnent for j 0 j lt nsems j printf 2d semns j printf AZent for j 0 j lt nsems j printf 2d semzs j putc n stdout else perror semctl IPC_STAT perror semget properly aligned 107 Chapter 4 Mutual Exclusion Example Uses of semop The program in Example 4 6 semop performs one or more semaphore operations ona set you specify You can use it to specify any sequence of operations including nonsensical sequences from the command line The command arguments are k key Numeric key to identify the semaphore set for example k 99 iid Semaphore ID number alternative to specifying the key n Apply IPC_NOWAIT to all following operations u Apply SEM_UNDO to all foll
56. A semaphore initialized to n represents the population of the buffer pool The pool itself might be implemented as a LIFO queue The right to update the queue anchor either to remove a buffer or to return one is a separate resource that is guarded by a lock The procedure for obtaining a buffer from the pool is as follows 1 Perform P on the pool semaphore When the operation completes you are assured there is at least one buffer in the pool and you are also assured that the count representing the buffer you need has been decremented from the semaphore 2 Claim the lock that guards the buffer queue anchor This ensures that there will be no conflict with another process taking or returning a buffer at the same time 3 Remove one buffer from the queue updating the queue anchor Step 1 assures that the queue is not empty 4 Release the lock on the queue anchor Overview of Mutual Exclusion The procedure for returning a buffer to the pool is as follows 1 Claim the lock that guards the buffer queue anchor This ensures that there will be no conflict with another process taking or returning a buffer at the same time 2 Put the returned buffer back on the queue updating the queue anchor The queue could be empty at this time 3 Release the lock on the queue anchor 4 Perform V on the pool semaphore This announces that at least one additional buffer is now free and may unblock some process waiting for a buffer The sa
57. But in order to inform the localizer as to what strings to translate and how they should comprise a catalog the application developer should provide a catalog for the developer s locale Opening and Closing XPG 4 Catalogs catopen locates and opens a message catalog file include lt nl_types h gt nl_catd catopen char name int unused Strings and Message Catalogs The argument name is used to locate the catalog Usually this is a simple relative pathname that is combined with environment variables to indicate the path to the catalog see XPG 4 Catalog Location for details However the catalog assumes names that begin with are absolute pathnames Use of a hard coded pathname like this is strongly discouraged it doesn t allow the user to specify the catalog s locale through environment variables When an application is finished using a message catalog it should close the catalog and free the descriptor using catclose int catclose nl_catd Using an XPG 4 Catalog Catalogs contain sets of numbered messages The application developer must know the contents of the catalog in order to specify the set and number of a message to be obtained catgets is used to retrieve strings from a message catalog see the catopen 3 and catgets 3 reference pages Example 16 3 shows a program that reads the first message from the first message set in the appropriate catalog and displays the result Example 16
58. Creating a Fontset Creating fontsets in X is simply a matter of providing a string that names the fonts as described above Example 16 6 Creating a Fontset XFontSet fontset char base_name should get from resource char missingCharsetList int missingCharsetCount char defaultStringForMissingCharsets base_name fixed medium r 150 use resources fontset XCreateFontSet display base_name missingCharsetList missingCharsetCount amp defaultStringForMissingCharsets The locale in effect at create time is bound to the fontset Fontsets are freed with XFreeFontSet Using a Fontset Fontsets are used when rendering text with X11R6 Xmb or Xwe text rendering routines These routines are described in Text Rendering Routines 387 Chapter 16 Internationalizing Your Application 388 Text Rendering Routines X11R6 includes text rendering routines that understand multibyte and wide character strings These routines are analogous to the X11R4 text rendering routines XDrawText XDrawString and XDrawImageString The old routines continue to operate but do not take fontsets and don t know how to handle characters longer than one byte e XmbDrawText and XwcDrawText take lists of TextItems each of which contains among other things a string The strings are rendered using fontsets These routines allow complex spacing and fontset shifts between strings e XmbDrawStrin
59. DPS AFM there is one font metric file per typeface When you install a font module such as the Japanese Font Module metric files for CID keyed fonts are stored in the directory usr lib X11 fonts CID character collection AFM Font metric files are primarily used by text processing and desktop publishing programs to for example generate PostScript code for a specified document Creating Font Aliases If you do not want to use long X font names you can specify shorter aliases for those names Silicon Graphics uses a file called fonts alias to specify short aliases for fonts There can be a fonts alias file in an X font directory For example see the file fonts alias in the directory usr lib X11 fonts 100dpi 321 Chapter 15 Working With Fonts 322 A typical font alias looks like this fixed misc fixed medium r semicondensed 13 120 75 75 c 60 is08859 1 This associates the short alias fixed to the longer name that follows it The alias file can also be used to specify alternate conventions for the component parts of a 14 part font name For example the following entry creates an alias that uses regular instead of medium for the weight component adobe utopia regular i normal 14 100 100 100 p 74 iso08859 1 adobe utopia medium i normal 14 100 100 100 p 74 1is08859 1 To specify your own font aliases in a font directory store them in a file called fonts alias local in that directory
60. Expressions 366 Cultural Data 368 NLS Interfaces 370 NLS Utilities 370 NLS Library Functions 371 XSI Curses Interface 371 Strings and Message Catalogs 372 XPG 4 Message Catalogs 372 Opening and Closing XPG 4 Catalogs 372 Using an XPG 4 Catalog 373 XPG 4 Catalog Location 374 Creating XPG 4 Message Catalogs 374 Compiling XPG 4 Message Catalogs 375 SVR4 MNLS Message Catalogs 376 Putting MNLS Strings Into a Catalog 376 Using MNLS in Shell Scripts 376 Specifying MNLS Catalogs 377 Getting Strings From MNLS Message Catalogs 377 Using pfmt 378 Labels Severity and Flags 378 Format Strings for pfmt 379 Using fmtmsg 379 Internationalizing File Typing Rule Strings With MNLS 380 Variably Ordered Referencing of printf Arguments 381 Internationalization Support in X11R6 383 Limitations of X11R6 in Supporting Internationalization 383 Vertical Text 384 Character Sets 384 Xlib Interface Change 384 Resource Names 385 XX Contents Getting X Internationalization Started 385 Initialization for Toolkit Programming 385 Initialization for Xlib Programming 385 Fontsets 386 Example EUC in Japanese 386 Specifying a Fontset 386 Creating a Fontset 387 Using a Fontset 387 Text Rendering Routines 388 New Text Extents Functions 388 Internationalization Support in Motif 390 xxi Contents Translating User Input 391 About User Input and Input Methods 391 Reuse Sample Code 392 GLInput 392 About X Keyboard Support 392 Keys Keycod
61. Fixed Offsets In rare cases you may need to create two or more mapped segments with a fixed relationship between their base addresses This would be the case when there are offset values in one segment that refer to the other segment as diagrammed in Figure 1 1 21 Chapter 1 Process Address Space 22 Offset A Y Offset S Figure 1 1 Segments With a Fixed Offset Relationship In Figure 1 1 a word in one segment contains an offset value A giving the distance in bytes to an object in a different mapped segment Offset A is accurate only when the two segments are separated by a known distance offset S You can create segments in such a relationship using the following procedure 1 Map a single segment large enough to encompass the lengths of all segments that need fixed offsets Use 0 for addr allowing IRIX to pick the base address Let this base address be B 2 Map the smaller segments over the larger one For the first the one at the lowest relative position specify B for addr and MAP_FIXED in flags 3 For the remaining segments specify B S for addr and MAP_FIXED in flags The initial large segment establishes a known base address and reserves enough address space to hold the other segments The later mappings replace the first one which cannot be used for its own sake Segments at a Fixed Address You can specify any value for addr IRIX creates the mapping if there is no
62. IPC_STAT is declared in the sys shm h header file The first field shm_perm is an ipc_perm structure This structure is declared in the sys ipc h header file Shared Memory Examples The example programs in this section illustrate the use of some of the SVR4 shared memory system functions Example of Creating a Shared Segment The program in Example 3 5 illustrates the use of shmget You can specify command parameters to exercise any combination of shmget function arguments Example 3 5 shmget System Call Example Program to test shmget 2 for creating a segment shmget k lt key gt s lt size gt p lt perms gt c x k lt key gt the key to use default 0 IPC_PRIVATE s lt size gt size of segment default is 64KB p lt perms gt permissions to use default is 0600 x use IPC_EXCL C use IPC_CREAT A include lt unistd h gt for getopt include lt sys shm h gt for shmget etc include lt errno h gt errno and perror include lt stdio h gt int main int argc char argv key_t key IPC_PRIVATE key size_t size 65536 size int perms 0600 permissions int shmflg 0 flag values struct shmid_ds ds info struct int c shmid whil 1 1 c getopt argc argv k s p cx switch c 73 Chapter 3 Sharing Memory Between Processes case k key key
63. IRIX Admin Disks and Documents the administration of XFS and XLV in general and Filesystems GRIO volumes in particular grio 5 Reference page giving an overview of GRIO use grio 1M Reference page for the administrator command for querying the state of the GRIO system ggd 1M Reference page for the GRIO grant daemon grio_disks 4 Reference page for the configuration files prepared by the administrator to name GRIO devices About Types of Guarantees GRIO offers two types of guarantee a real time sometimes called hard guarantee and a non real time or soft guarantee The real time guarantee promises to subordinate every other consideration including especially data integrity to on time delivery The two types of guarantee are effectively the same as long as no I O read errors occur When a read error occurs under a real time guarantee no error recovery is attempted the read function simply returns an error indication Under a non real time guarantee I O error recovery is attempted and this can cause a temporary failure to keep up to the guaranteed bandwidth You can qualify either type of guarantee as being Rotor scheduling also known as Video On Demand VOD This indicates a particular special use of a striped volume These three types of guarantee and several other options are described in detail in IRIX Admin Disks and Filesystems and in the grio 5 reference page About Device Configuration GRI
64. Initially a timer is disarmed inactive You start a timer by calling timer_settime The principal argument to this function is an itimerspec_t object which contains two times One it_value specifies when the timer next expires The other it_interval is the value to be loaded into the timer when it expires You can call timer_settime to accomplish any of three different operations e With it_value nonzero and it_interval zero arm the timer and initiate a one time interval e With it_value nonzero and it_interval nonzero arm and initiate a repeating timer e With it_value zero disarm the timer preventing it from expiring if it has not expired already You can also use timer_settime to reprogram the intervals in a timer while it runs A timer can be programmed in terms of relative time you pass an it_value that represents increments past the present time or absolute time you pass an it_value that represents actual future times when the timer should expire You can interrogate the time remaining in a timer by calling timer_gettime After a timer has expired for example in the signal handling function you can call timer_getoverrun to find out how many additional intervals it would have signalled but could not signal because the first signal was pending BSD Timers IRIX supports the BSD UNIX feature of interval timers or itimers Table 5 10 summarizes the functions you use to manage itimers Table 5 10
65. Locale Specific Behavior on page 359 which describes native language support regular expressions and cultural data Setting the Current Locale Applications begin in the C locale C is the name used to indicate the system default locale it usually corresponds to American English Applications should therefore call setlocale as soon as possible to put the process into the desired locale The syntax for setlocale is include lt locale h gt char setlocale int category const char locale The call almost always looks either like this if setlocale LC_ALL NULL exit_with_error Using Locales or like this if setlocale LC_ALL NULL setlocale LC_ALL C Details of the two parameters are given in the next two sections Using Locale Categories Applications need not perform every aspect of their work in the same locale Although this approach is not recommended an application could for example perform most of its activities in the English locale but use French sorting rules You can use locale categories to do this kind of locale mixing Mixing locale categories is not the same as multilingual support see Multilingual Support The category argument is a symbolic constant that tells setlocale which items in a locale to change Table 16 1 lists the available category choices Table 16 1 Locale Categories Category Affects LC_ALL All categories below L
66. NLSPATH 374 opening 373 reading 373 specifying MNLS 377 XPG 3 about 372 compiling 375 creating 374 using 373 message queue 137 172 comparing POSIX SVR4 138 overview of 138 140 POSIX facilities 140 154 SVR4 facilities 155 172 use of 140 425 Index Mexico country code 417 MIPS ABI reserved address space 23 mmap 12 23 and file permissions 17 and NFS mounted files 17 in place of lseek 17 of dev mem 20 of dev mmem 20 of dev vme 20 of zero segment 19 parameters of 13 19 POSIX use 55 using specified addresses 22 when swap is allocated 15 MNLS Also see message catalogs message catalogs 376 381 monitor resolution 312 Motif internationalization 390 MPI 253 differences from PVM 304 306 msync 15 29 multibyte characters See internationalization multibyte characters multilingual support 345 multithreading See parallel computation pthreads mutex 79 mutual exclusion 78 112 289 299 barrier 82 condition variable 81 292 297 IRIX facilities 87 96 lock 79 mutex 79 289 292 POSIX facilities 82 86 read write locks 298 299 semaphore 80 SVR4 facilities 96 112 test and set 78 426 N names country 415 nationalized software 336 New Zealand country code 417 NFS and file locking 192 NFS and memory mapped files 17 Nigeria country code 417 NLSPATH 374 0 Off the Spot style 398 On the Spot style 399 open 13 example code 239 of de
67. Read or write to broken pipe see pipe 2 read 2 write 2 SIGALRM 14 Terminate Interval timer elapsed see Timer Facilities on page 127 SIGTERM 15 Terminate Process terminated SIGUSR1 16 Terminate Programmer defined see also text below SIGUSR2 17 Terminate Programmer defined SIGCHLD or 18 Terminate Child process status change see wait 2 and SIGCLD Process Reaping on page 265 SIGPWR 19 Ignore Power fail restart SIGWINCH 20 Ignore Change in size of window see xterm 1 SIGURG 21 Ignore Urgent socket condition see socket 2 SIGPOLL 22 Terminate Pollable event from a STREAMS device see streamio 7 SIGIO 22 Terminate Input output possible SIGSTOP 23 Suspend Stopped SIGTSTP 24 Suspend Stop key signal from controlling terminal see termio 7 SIGCONT 25 Ignore Continued SIGTTIN 26 Suspend Attempt to read terminal from background process see termio 7 SIGTTOU 27 Suspend Attempt to write terminal from background process see termio 7 SIGVTALRM 28 Terminate Virtual timer expired see getitimer 2 SIGPROF 29 Terminate Profiling timer expired see getitimer 2 115 Chapter 5 Signalling Events 116 Table 5 1 Signal Numbers and Default Actions continued Symbolic Numeric Name Value Default Action Normal Meaning SIGXCPU 30 SIGXFSZ 31 no symbol 32 48 SIGRTMIN 49 64 SIGRTMAX Terminate and dump CPU time limit exceeded see getrlimit 2 Terminate and dump File size
68. Scheduling Priority on page 288 Table 13 6 Functions for Schedule Management Function Purpose pthread_getschedparam 3P Get a thread s policy and priority pthread_setschedparam 3P Set a thread s policy and priority sched_get_priority_max 3C Return the maximum priority value sched_get_priority_min 3C Return the minimum priority value sched_yield 2 Relinquish the processor pthread_setconcurrency 3P Modify concurrency level pthread_getconcurrency 3P Check the concurrency level pthread_setrunon_np 3P Select a CPU to run a system scope thread pthread_getrunon_np 3P Query a named CPU s affinity Scheduling Policy There are two scheduling policies in this implementation first in first out SCHED_FIFO and the default round robin GSCHED_RR SCHED_FIFO and SCHED_RR are similar The round robin scheduler ensures that after a thread has used a certain maximum amount of time it is moved to the end of the queue of threads of the same priority and can be preempted by other threads The details of scheduling are discussed in the pthread_attr_setschedpolicy 3P reference page 287 Chapter 13 Thread Level Parallelism Scheduling Priority Threads are ordered by priority values with a small number representing a low priority and a larger number representing a higher priority Threads with higher priorities are chosen to execute before threads with lower priorities The sched_get_priority_max and sch
69. Signal Numbers and Default Actions 114 Signal Handling Interfaces 116 Functions for POSIX Signal Handling 121 Functions for SVR4 Signal Handling 125 Functions for BSD Signal Handling 126 Functions for Timed Suspensions 127 Time Data Structures and Usage 128 POSIX Time Management Functions 130 POSIX Time Management Functions 130 BSD Functions for Interval Timers 134 Types of itimer 135 Abstract Operations on a Message Queue 138 POSIX Functions for Managing Message Queues 141 POSIX Functions for Using Message Queues 143 SVR4 Functions for Managing Message Queues 155 SVR4 Functions for Using Message Queues 157 Functions for File and Record Locking 176 Comparing Parallel Models 248 Documentation for Statement Level Parallel Products 256 Loop Scheduling Types 259 Commands and System Functions for Process Management 262 Functions for Child Process Management 265 Commands and Functions for Scheduling Control 266 POSIX Functions for Scheduling 268 Comparison of Pthreads and Processes 274 Header Files Related to Pthreads 276 Functions for Creating Pthreads 277 Functions for Managing Thread Execution 280 Functions for Thread Unique Data 284 Functions for Schedule Management 287 Functions for Preparing Mutex Objects 290 Functions for Using Mutexes 292 Functions for Preparing Condition Variables 293 List of Tables Table 13 10 Table 13 11 Table 13 12 Table 15 1 Table 16 1 Table 16 2 Table 16 3 Table 16 4 Table 16 5 Tab
70. Table 3 5 IRIX Shared Memory First Datum Functions Function Name Purpose and Operation usputinfo 3 Set the shared pointer field of an arena to a value usgetinfo 3 Retrieve the value of the shared pointer field of an arena uscasinfo 3 Change the shared pointer field using a compare and swap Note The precision of the usgetinfo field in an arena 32 or 64 bits depends on the execution model of the program that creates the arena This is one reason that processes compiled to different models cannot share one arena see Sharing Memory Between 32 Bit and 64 Bit Processes on page 54 Often the parent process creates and initializes the arena before it creates any of the child processes that will share the arena In this case you expect no race conditions The parent can set the shared pointer using usputinfo because no other process is using the arena at that time Each child process can fetch the value with usgetinfo The purpose of uscasinfo is to change the contents of the field in an atomic fashion avoiding any race condition between concurrent processes in a multiprocessor All three functions are discussed in detail in the usputinfo P reference page Tip The data type of the shared pointer field is void a 64 bit value when the program is compiled to the 64 bit model If you need to cast the value to an integer use the type __psint_t a pointer sized integer in any model IRIX Shared Memory Arenas In the le
71. Table i Books for Further Reading in IRIX Development Topic Document Title Number Overview of the IRIX library of Programming on Silicon Graphics Systems An 007 2476 nnn manuals for developers Overview Compiling linking and tuning MIPSpro Compiling and Performance Tuning Guide 007 2360 nnn programs in C C or Fortran Writing modules in assembly MIPSpro Assembly Language Programmer s Guide 007 2418 nnn language C language C Language Reference Manual 007 0701 nnn C language C Language System Overview 007 1621 nnn Fortran language MIPSpro Fortran 77 Programmer s Guide 007 2361 nnn MIPSpro Fortran 90 Programmer s Guide 007 2761 nnn System Configuration IRIX Admin System Configuration and Tuning 007 2859 nnn Writing real time applications REACT Pro Real Time Programmer s Guide 007 2499 nnn Controlling devices directly IRIX Device Driver Programmer s Guide 007 0911 nnn Details of the MIPS processor MIPS R4000 Microprocessor User s Manual hardware xxxiv About This Manual You can find additional information about internationalization from X Open Company Limited X Open Portability Guide Volume 1 XSI Commands and Utilities Volume 2 XSI System Interface and Volume 3 XSI Supplementary Definitions Berkshire United Kingdom Prentice Hall Inc Obtaining Manuals Silicon Graphics manuals are usually read online using IRIS InSight This manual and many of the books in Table i are installed as part of the I
72. Then the thread calls deleteInList This function changes the list so it begins by acquiring the list mutex Then it can safely modify the list pointers It scans up the list looking for the pointer that points to the target element It removes the target element from the list by copying its next field to replace the pointer to the target element With the element removed from the list deleteInList calls pthread_cond_broadcast to wake up all threads not just the first thread that might be waiting for the element to become nonbusy Each of these threads resumes execution at point A by attempting to re acquire the list mutex However deleteInList is still holding the list mutex The mutex is released then the other threads can resume execution following point A but this time when they search the list the desired key is no longer found Meanwhile deleteInList uses pthread_cond_destroy to release any memory that the pthreads library might have associated with the condition variable before releasing the list element object itself 297 Chapter 13 Thread Level Parallelism 298 Read Write Locks A read write lock is a software object that gives one thread the right to modify some data or multiple threads the right to read that data A read write lock can be owned for write or for read If acquired for write only one thread can own it and other threads must wait If acquired for read other threads wishi
73. a File for Record Locking The first requirement for locking a file or segment of a file is having a valid open file descriptor If read locks are to be used then the file must be opened with at least read access likewise for write locks and write access Example 7 1 opens a file for both read and write access Example 7 1 Opening a File for Locked Use include lt stdio h gt include lt errno h gt include lt fcntl h gt int fd file descriptor char filename main argc argv int argc char argv 179 Chapter 7 File and Record Locking 180 extern void exit perror get database file name from command line and open the file for read and write access Ef if argc lt 2 void fprintf stderr usage s filename n argv 0 exit 2 filename argv 1 fd open filename O_RDWR if fd lt 0 perror filename exit 2 The file is now open to perform both locking and I O functions The next step is to set a lock Setting a File Lock Several ways exist to set a lock on a file These methods depend upon how the lock interacts with the rest of the program Issues of portability and performance need to be considered Three methods for setting a lock are given here using the fentl system call using the usr group standards compatible lockf library function and using the BSD compatible flock library function Locking an entire file is just a special case of
74. ability to create intelligible text An internationalized version of the above code appears in Example 16 4 Example 16 4 Internationalized Code internationalized XPG 4 version char form catgets msgd set formNum At 1 s I bought 2 s n char store catgets msgd set storeNum Macy s char obj catgets msgd set ob jNum a cup printf form store obj The unlocalized default version would produce At Macy s I bought a cup A localized version might produce Compr una tasa en Macy s In practice variably ordered format strings are found only in message catalogs and not in default strings The default string usually simply uses the parameters in the order they re given without the new variable order format strings Internationalization Support in X11R6 Internationalization Support in X11R6 X11R6 internationalization support is provided on the X client side that is the application must take care of such support instead of relying on the X server No server changes are necessary and the protocol is unchanged Full backward compatibility is preserved so a new internationalized application can run on an old server Note X11R6 internationalization refers to features in X11R5 and X11R6 X uses existing internationalization standards to do its internationalization support there are no X specific interfaces to set and change locale Internationalized X applications receive no he
75. access Using Record Locking discusses the use of file and record locks to get exclusive data access Enforcing Mandatory Locking describes how file locks can be made mandatory on programs that do not use locking Record Locking Across Multiple Systems discusses how file locking can be extended to NFS mounted files 175 Chapter 7 File and Record Locking Overview of File and Record Locking 176 Simultaneous access to file data is characteristic of many multiprocess multithreaded or real time applications The purpose of the file and record locking facility is to provide a way for programs to synchronize their use of common file data Advisory file and record locking can be used to coordinate independent unrelated processes In mandatory locking on the other hand the standard I O subroutines and I O system calls enforce the locking protocol Mandatory locking keeps unrelated programs from accessing data out of sequence at some cost of access speed The system functions used in file and record locking are summarized in Table 7 1 Table 7 1 Functions for File and Record Locking Function Name Purpose and Operation fentl 2 fentl 5 General function for modifying an open file descriptor can be used to set file and record locks lockf 3C lockf 3F Library function to set and remove file and record locks on open files SVR4 compatible flock 3B Library function to set and remove file and record l
76. allocated in the node where the program that first defines that page is executing When that is not possible the memory is allocated as close as possible in router hops to the CPU that first accessed the page e The IRIX scheduler maintains process affinity to CPUs based on both cache affinity as in previous versions and on memory affinity When a process is ready to run it is dispatched to The CPU where it last ran if possible The other CPU in the same node if possible A CPU ina nearby node The great majority of commands and user programs have memory requirements that fit comfortably in a single node and most execute at least as well usually faster than in any previous Silicon Graphics system 33 Chapter 1 Process Address Space 34 About Large Memory Use Only one memory performance issue arises with a single threaded program When the program allocates much more virtual memory than is physically available in its node at least some of its virtual address space is allocated in other nodes The program pays an access time penalty on some segments of its address space When this occurs the penalty is usually unnoticeable as long as the program has good cache behavior Typically IRIX allocates the first requested memory in the requester s node When the first requested memory is also the most used average access time still remains low When this is not the case there are tools you can use to ensure that specific
77. also vary Even though we assume that decimal numbers are universal there are some eighteen varying aspects of numeric formatting defined by a locale Many of these are details of monetary formatting 355 Chapter 16 Internationalizing Your Application 356 For example Germany uses a comma to denote a decimal radix and a period to denote a group separator English reverses these India groups digits by two except for the last three digits before the decimal radix Many locales have particular formats used for money some of which are shown in Table 16 3 Table 16 3 Some Monetary Formats Country Positive Format Negative Format India Rs1 02 34 567 89 Rs 1 02 34 567 89 Italy L 10 234 567 L 10 234 567 Japan 10 234 567 10 234 567 Netherlands F10 234 567 89 F 10 234 567 89 Norway Kr10 234 567 89 Kr10 234 567 89 Switzerland SFr10 234 567 89 SFr10 234 567 89C Using printf printf function detailed in the printf 3S reference page examines LC_NUMERIC and chooses the appropriate decimal radix If none is available it tries to use ASCII period No further locale specific formatting is done directly by printf However see Variably Ordered Referencing of printf Arguments for a way to handle locale specific ordering of syntactic elements in messages Using localeconv The localeconv function detailed in the localeconv 3C reference page can be called to find out about numeric formatting data inclu
78. an internationalized program is one that can be easily localized without changing the program itself See Localization 110n below for an explanation of the term localization Note The word internationalization consists of ani followed by 18 letters followed by an n It is thus often abbreviated i18n in informal writing On similar principles localization is often abbreviated 110n A program written for a specific locale may be difficult to run in a different environment Rewriting such a program to operate in each desired environment would be tedious and costly Your goal as a developer should thus be to write locale independent programs programs that make no assumptions about languages local customs or coded character sets Such internationalized applications can run in a user s native environment following native conventions with native messages without recompiling or relinking A single copy of an internationalized program can be used by a world of different users Localization 110n Localization is the act of providing an internationalized application with the environment and data it needs to operate in a particular locale For example adding German system messages to IRIX is a part of localizing IRIX for the German locale 335 Chapter 16 Internationalizing Your Application 336 Nationalized Software Nationalized programs run in only one language and are governed by one set o
79. an optimized parallel program is as follows 1 Write a complete application that runs on a single processor Completely debug and verify the correctness of the program in serial execution 2 3 Apply the source analyzer and study the listing it produces 4 Add assertions to the source program These are not explicit commands to parallelize but high level statements that describe the program s use of data g Repeat steps 3 and 4 until the analyzer finds as much parallelism as possible Run the program on a single memory multiprocessor 257 Chapter 11 Statement Level Parallelism When the program requires maintenance you make the necessary logic changes and simultaneously remove any assertions about the changed code unless you are certain that the assertions are still true of the modified logic Then repeat the preceding procedure from step 2 Managing Statement Parallel Execution 258 The run time library for all three languages is the same libmp It is documented in the mp 3 reference page libmp uses IRIX lightweight processes to implement parallel execution see Chapter 12 Process Level Parallelism When a parallel program starts the run time support creates a pool of lightweight processes using the sproc function Initially the extra processes are blocked while one process executes the opening passage of the program When execution reaches a parallel section the run time library code unblocks as m
80. and makes it legitimate for the function to change the busy flag in an element When it finds the element the function might discover that the element is already busy In this case it must wait for the event element is no longer busy which is represented by the condition variable notBusy in the element In order to wait for this event getFromList calls pthread_cond_wait passing its list mutex and the condition variable point A in the code This releases the list mutex so that other threads can acquire the list and do their work on other elements When any thread wants to release the use of a list element it calls freeInList After clearing the busy flag in the list element freeInList announces that the event element is no longer busy has occurred by calling pthread_cond_signal This call releases a thread that is waiting at point A If there is more than one thread waiting for the same element the first in priority order is released The released thread re acquires the list mutex and resumes execution The first thing it does is repeat its search of the list for the desired key and on finding the element again test it again for busyness This repetition is needed because it is possible to get spurious returns from a condition variable When a thread wants to delete a list element it gets the list element by calling getFromList This ensures that the element is busy so no other thread is using it
81. and stack segments and any mapped segments made with MAP_PRIVATE as they are defined at the time of the call If you extend these segments after locking them the newly defined pages are also locked as they are defined Although new pages are locked when they are defined you still should extend these segments to their maximum size while initializing the program The reason is that it takes time to extend a segment the kernel must process a page fault and create a new page frame possibly writing other pages to backing store to make space One way to ensure that the full stack is created before it is locked is to call plock from a function like the function in Example 1 2 Example 1 2 Function to Lock Maximum Stack Size define MAX_STACK_DEPTH 100000 your best guess int call_plock char dummy MAX_STACK_DEPTH return plock PROCLOCK The large local variable forces the call stack to what you expect will be its maximum size before plock is entered The plock function does not lock mapped segments you create with MAP_SHARED You must lock them individually using mpin You need to do this from only one of the processes that shares the segment Locking Mapped Segments It may be better for your program to not lock the entire address space but to lock only a particular mapped segment Immediately after calling mmap you have the address and length of the mapped segment This is a convenient time to
82. are satisfied from the secondary cache which is connected directly to the CPU e The CrayLink interconnection fabric has an extremely high bandwidth in excess of 600MB sec sustained bidirectionally on every link so each router hop adds only a small fraction of a microsecond to the access time Performance problems only arise when multithreaded programs defeat the caching algorithms or place high bandwidth memory demands from multiple CPUs to a single node Cache Coherency Each CPU in an Origin system has an independent secondary cache organized as a set of 128 byte cache lines The memory lines that were most recently used by the CPU are stored here for high speed access When two or more CPUs access the same memory each has an independent copy of that data There can be as many copies of a data item as there are CPUs and for some important tables in the IRIX kernel this may often be the case 31 Chapter 1 Process Address Space 32 Cache coherency means that the system hardware ensures that every cached copy remains a true reflection of the memory data without software intervention Cache coherency requires no effort as long as all CPUs merely read the memory data The hardware must intervene when a CPU attempts to modify memory Then that CPU must be given exclusive ownership of the modified cache line and all other copies of the same data must be marked invalid so that when the other CPUs need this data they will f
83. bandwidth e The program has a high CPU utilization so it is not being delayed for I O or by synchronization with other threads e The program has no other performance problems that can be detected with perfex of the Speedshop tools see the speedshop 1 reference page Using Origin2000 Nonuniform Memory There are two issues to make sure that each thread concentrates memory access on some definable subset of the data and second to make sure that this data is allocated on or near the node where the thread executes The first issue is algorithmic It is not possible for a page of data to be in two nodes at once When data is used simultaneously by two or more threads that data must be closer to some threads than to others and it must be delivered to all threads from a single hub chip Parenthetically what is true of data is not necessarily true of program text which is read only The kernel can and does replicate the pages of common DSOs in every node so that there is no time penalty for fetching instructions from common DSOs like the C or Fortran runtime libraries Programming Desired Memory Placement When you have a clear separation of data between parallel threads there are several tools for placing pages near the threads that use them The tool you use depends on the model of parallel computation you use e Using the Fortran compiler specify how array elements are distributed among the threads of a parallelized loop usin
84. be greater than that height It may include additional vertical spacing that is considered part of the font design Typographers use small units of measure called points to specify font size A point is approximately equal to 1 72 of an inch The exact value is 1 72 27 0 013837 of an inch or 0 351 mm A point is a device independent unit of measure Its size does not depend on the resolution of an output device A 12 point font should have approximately the same size on different output devices regardless of the resolution of those devices Font Basics If the resolution of an output device is equal to 72 dots per inch dpi the size of a dot or pixel is approximately equal to the size of a point If the resolution of an output device is greater than 72 dpi the size of a dot or pixel is smaller than the size of a point and vice versa You can use the following formula to calculate a pixel size from a point size pixel siz point size x device resolution 72 27 A bitmap font is usually designed for a particular resolution Such a font has the point size specified by its designer only when it is used on an output device whose resolution matches the resolution for which that font was designed This is because a font designer specifies a fixed bitmap for each character If a pixel is smaller than a point characters will be smaller than intended and vice versa Font Names When a font is designed it is assigned a name such as C
85. call either mpin Q or mlock to lock the mapped segment 25 Chapter 1 Process Address Space 26 The mmap flags MAP_AUTOGROW and MAP_AUTORESRYV are unique to IRIX and not defined by POSIX However the POSIX mlock function for IRIX does recognize autogrow segments If you lock an autogrow segment with mpin mlock or mlockall with the MCL_FUTURE flag additional pages are locked as they are added to the segment If you lock the segment with mlockall with the MCL_CURRENT flag the segment is locked for its current size only and added pages are not locked Locking Mapped Files If you map a file before you use mlockall MCL_CURRENT or plock to lock the data segment into memory see Mapping a File for I O on page 15 the mapped file is read into the locked pages during the lock operation If you lock the program with mlockall MCL_FUTURE and then map a file into memory the mapped file is read into memory and the pages locked If you map a file after locking the data segment with plock or mlockall MCL_CURRENT the new mapped segment is not locked Pages of file data are read on demand as the program accesses them From these facts you can conclude the following e You should map small files before locking memory thus getting fast access to their contents without paging delays e Conversely if you map a file after locking memory your program could be delayed for input on any access to the mapped segment
86. case i id msqid int break strtoul optarg NULL 0 case t type case b bytes bytes strtoul optarg NULL 0 break type strtoul optarg NULL 0 167 Chapter 6 Message Queues if bytes lt 32 bytes 32 break case c count count strtoul optarg NULL 0 if count gt 99999 count 99999 break case n nowait msgflg IPC_NOWAIT break default unknown or missing argument return 1 msg struct msgspace calloc 1 sizeof long bytes if 1 msqid no id given try key msqid msgget key 0 if 1 msqid const time_t tm time NULL char stime 26 void ctime_r amp tm stime format timestamp for msg stime 24 0 drop annoying n for c 1 c lt count c msg gt type type sprintf msg gt text S05d s c stime if 1 msgsnd msqid msg bytes msgflg else 168 perror msgsnd break perror msgget System V Message Queues Example of msgrcv The program msgrcv in Example 6 8 allows you to receive messages from a specified queue The following arguments are used in more than one program k key Numeric identifier of a message queue for example k 99 iid Message queue ID alternative to specifying the key for example i 80 c count Number of messages to attempt to receive
87. chapter provides information on how to make your applications more widely accessible This section presents the following topics e Some Definitions of Internationalization covers locales internationalization localization nationalized software and multilingual software e Areas of Concern in Internationalizing Software points out a few concerns to watch for when internationalizing your software e Standards covers standard compliant features e Internationalizing Your Application The Basic Steps lists the procedures to use when internationalizing an icon e Additional Reading on Internationalization provides references you can consult for additional information about internationalization Overview of Internationalization Some Definitions of Internationalization This section defines some of the terms used in this chapter Locale Locale refers to a set of local customs that determine many aspects of software input and output formatting including natural language culture character sets and encodings and formatting and sorting rules The locale of a program is the set of such parameters that are currently selected For information on the method for selecting locales see Additional Reading on Internationalization below Internationalization i18n Internationalization is the process of making a program capable of running in multiple locales without recompiling To put it another way
88. conflict with an existing segment or returns an error if the mapping is impossible However you cannot normally tell what virtual addresses will be available for mapping in any particular installation or version of the operating system There are three exceptions First after IRIX has chosen an address for you you can always map anew segment of the same or shorter length at the same address This allows you to map different parts of a file into the same segment at different times see Mapping Portions of a File on page 17 Locking and Unlocking Pages in Memory Second the low 4 MB of the address space are unused see Address Space Boundaries on page 4 It is a very bad idea to map anything into the 0 page because that makes it hard to trap the use of uninitialized pointers But you can use other parts of the initial 4 MB for mapping Third the MIPS Application Binary Interface ABI specification an extension of the System V ABI published by AT amp T states that addresses from 0x3000 0000 through Ox3ffc 0000 are reserved for user defined segment base addresses You may specify values in this range as addr with MAP_FIXED in flags When you map two or more segments into this region no two segments can occupy the same 256 KB unit This rule ensures that segments always start in different pages even when the maximum possible page size is in use For example if you want to create two segments each of 4096 bytes you can pla
89. creates many processes can quickly run into the rlimit_vumem_max boundary Delayed and Immediate Space Definition IRIX supports two radically different ways of defining segments of address space The conventional behavior of UNIX systems and the default behavior of current releases of IRIX is that space created using brk or malloc is immediately defined Page table entries are created to define the addresses and swap space is allocated as a backing store Three results follow from the conventional method e A program can detect immediately when swap space is exhausted A call to malloc returns NULL when memory cannot be allocated A program can test the limits of swap space by making repeated calls to malloc Chapter 1 Process Address Space A large memory allocation by one program can fill the swap disk partition causing other programs to see out of memory errors whether the program ever uses its allocated memory or not A fork or exec call fails unless there is free space in swap equal to the data and stack sizes of the new process By default in IRIX 5 2 and optionally in later releases IRIX uses a different method sometimes called virtual swap In this method the definition of new segments is delayed until the space is actually used Functions like brk and malloc merely test the new size of the data segment against the resource limits They do not actually define the new addresses and they do not cause
90. defines a number of multi byte functions and an additional function for manipulating monetary values At this stage the X Open definition is only guaranteed to work correctly for single byte 8 bit characters and thus does not include the multi byte functions 361 Chapter 16 Internationalizing Your Application 362 In addition X Open defines internationalized regular expression compile and match functions native language message handling functions and native language versions of the error handling functions see Table 16 5 Table 16 5 X Open Additional Functions Function Function continued catclose regexp catgets vfprintf catopen vprintf nl_langinfo vsprintf perror Native Language Support and the NLS Database The X Open NLS interface defines the functional capabilities of a generic database that holds various language dependent entities This section describes those entities e Configuration Data e Collating Sequence Tables e Character Classification Tables e Shift Tables e Language Information Configuration Data Configuration data identify the languages supported on a system in terms of the recognized settings of language territory and codeset Each valid combination of these settings has its own set of collating sequence character classification and shift tables language information data and message catalogs Locale Specific Behavior Co
91. dependent applications should not use it for I O strings or communication Multibyte Characters A multibyte character is a series of bytes The character itself contains information on how many bytes long it is Multibyte characters are referenced as strings and are therefore of type char before parsing a string is indistinguishable from a multibyte character The zero byte is still used as a string and MB character terminator A string of MB characters can be considered a null terminated array of bytes exactly like a traditional string A multibyte string may contain characters from multiple codesets Usually this is done by incorporating special bytes that indicate that the next character and only the next character will be in a different codeset Very little application code should ever need to be aware of that though you should use the available library routines to find out information about multibyte strings rather than look at the underlying byte structure because that structure varies from one encoding to another For one example of an encoding that allows characters from multiple codesets see EUC on page 412 349 Chapter 16 Internationalizing Your Application 350 Use of Multibyte Strings Multibyte strings are very easy to pass around They efficiently use space both data and disk space since extra bytes are used only for characters that require them MB strings can be read and written without
92. dir This file is created by mkfontdir see the mkfontdir 1 reference page e The files usr lib X11 fonts ps2xlfd_map are used by the X Window System and the IRIS Font Manager to map PostScript names or short font names to 14 part X font names and vice versa The IRIS Font Manager does not use any bitmap fonts that do not have an entry in those files In IRIX 6 5 the twelve bitmap and outline fonts appear in the install directories e Dutch 801 Roman Dutch 801 Italic Dutch 801 Bold Dutch 801 Bold Italic e Swiss 721 Roman Swiss 721 Italic Swiss 721 Bold Swiss 721 Bold Italic e Courier 10 Pitch Roman Courier 10 Pitch Italic Courier 10 Pitch Bold and Courier 10 Pitch Bold Italic Each font contains 1015 characters Those characters adhere to the International Organization for Standardization IS08859 1 through ISO8859 10 and the Minimum European Subset MES of ISO10646 1 or Unicode 2 0 For more information about MES use a web browser to open http www mi uni koeln de c mirror www kostis net charsets isol10646 mes html from the source http www indigo ie egt standards mes html Swiss 721 fonts are installed when you install the subsystem x_eoe sw Xfonts The rest of the fonts are in the subsystem x_eoe sw Xunicodefonts The subsystem x_eoe sw Xfonts is installed by default while the subsystem x_eoe sw Xunicodefonts is optional The new fonts are sometimes referred to as Unicode fonts because they include Unicode character
93. does not contain input code but leaves that to the operating environment which in IRIX means X In short support for internationalized input means a departure from qread Under IRIX that means using mixed model input all the more reason to use a toolkit About X Keyboard Support This section provides some background that may help make the following sections easier to understand Translating User Input Keys Keycodes and Keysyms When a client connects to the X server the server announces its range of keycodes and exports a table of keysyms Each key event the client receives has a single byte keycode which directly represents a physical key and a single byte state which represents currently engaged modifier keys such as Shift or Alt Note The mapping of state bits to modifiers is done by another table acquired from the server Keysyms are well defined and there has been an attempt to have a keysym for every engraving one might possibly find on any keyboard anywhere An engraving is the image imprinted on a physical key These are contained in usr include X11 keysymdef h Keysyms represent the engravings on the actual keys but not their meanings The server s idea of the keysym table can be changed by clients and clients may receive KeyMap events when this remapping happens but such events don t happen often When a client receives a Key event it asks Xlib to use the keycode to index into its keysym table to fi
94. errno and perror include lt stdio h gt int main int argc char argv key_t key key int semid 1 object ID int nsops 0 setsize short flg 0 Le struct semid_ds ds int Gr s struct sembuf sops 25 while 1 c switch c and loop variable flag to use on all ops getopt argc argv k i p v z nu case k key key key_t strtoul optarg NUL 0 break case i semid semid int strtoul optarg NUL 0 break case n use nowait flg IPC_NOWAIT break case u use undo flg SEM_UNDO break case p do the P sops nsops sem_num ushort_t strtoul optarg NULL 0 sops nsops sem_op 1 sops nsopst sem_flg flg break case v do the V sops nsops sem_num ushort_t strtoul optarg NULL 0 sops nsops sem_op 1 sops nsopst sem_flg flg break case z do the wait for zero sops nsops sem_num ushort_t strtoul optarg NULL 0 sops nsops sem_op 0 sops nsopst sem_flg flg break 109 Chapter 4 Mutual Exclusion default unknown or missing argument return 1 if 1 semid i not given must have k semid semget key 0 0 if 1 semid if 0 semop semid sops nsops perror semop else perror semget Using the Examples The following commands demonstrate the use of the
95. file Mapping Physical Memory You can use mmap to create a segment that is a window on physical memory To do so you create a file descriptor by opening the special file dev mem For more information see the mem 7 reference page Obviously the use of such a segment is nonportable hardware dependent and dependent on the OS release Mapping Kernel Virtual Memory You can use mmap to create a segment that is a window on the kernel s virtual address space To do so you create a file descriptor by opening the special file dev mmem note the double m For more information see the mem 7 single m reference page The acceptable off and len values you can use when mapping dev mmem are defined by the contents of var sysgen master d mem Normally this file restricts possible mappings to specific hardware registers such as the high precision clock For an example of mapping dev mmem see the example code in the syssgi 2 reference page under the SGI_QUERY_CYCLECNTR argument Mapping a VME Device You can use mmap to create a segment that is a window on the bus address space of a particular VME bus adapter This allows you to do programmed I O PIO to VME devices Mapping Segments of Memory To do PIO you create a file descriptor by opening one of the special devices in dev ume These files correspond to VME devices For details on the naming of these files see the usrvme 7 reference page The name of th
96. file descriptor 2 Use lseek fd 0 SEEK_END to discover the size of the file see the lseek 2 reference page 3 Map the file with an off of 0 and len of the file size Apparent Process Size When you map a large file into memory the space is counted as part of the virtual size of the process This can lead to very large apparent sizes For example under IRIX 5 3 and 6 2 the Object Server maps a large database into memory with the result that a typical result of ps l looks like this 70 S 0 566 10 26 20 33481 225 80272230 0 45 objectser The total virtual size of 33481 certainly gets your attention However note the more modest real storage size of 225 Most of the mapped pages are not in physical memory Also realize that the backing store for pages of a mapped file is the file itself no swap space is used Mapping Segments of Memory Mapping Portions of a File You do not have to map the entire file you can map any portion of it from one page to the file size Simply specify the desired length as len and the starting offset as off You can remap a file to a different segment by calling mmap again In this way you can use the off parameter of mmap as the logical equivalent of lseek That is to map a different segment of the file specify e the same file descriptor e the new offset in off e the current segment base address as addr e MAP FIXED in flags to force the use of addr as the base address otherwis
97. function sproc which creates a lightweight process A process created with sproc shares some of its process state values with its parent process the sproc 2 reference page details how this sharing is specified In particular a process made with sproc does not have its own address space It continues to execute in the address space of the original process In this respect a lightweight process is like a thread see Thread Level Parallelism on page 249 However a lightweight process differs from a thread in two significant ways e A lightweight process still has a full set of UNIX state values Some of these for example the table of open file descriptors can be shared with the parent process but in general a lightweight process carries most of the state information of a process e Dispatch of lightweight processes is done in the kernel and has the same overhead as dispatching any process The library support for statement level parallelism is based on the use of lightweight processes see Statement Level Parallelism on page 251 Thread Level Parallelism A thread is an independent execution state within the context of a larger program The concept of a thread is well known but the most common formal definition of threads and their operation is provided by POSIX standard 1003 1c System Application Program Interface Amendment 2 Threads Extension 249 Chapter 10 Models of Parallel Computation 250
98. given aiocb for only one operation at a time and to not modify an aiocb until its operation is complete You can schedule a list of operations using lio_listio see the lio_listio 3 reference page The advantage of this function is that you can request a single notification either a signal or a callback when all of the operations in the list are complete Alternatively you can be notified of the completion of each one as it happens When an asynchronous I O thread is free it takes a queued aiocb and performs the equivalent function to Iseek if a file position is specified then the equivalent of read or write The asynchronous process may be blocked for some time That depends on the file or device and on the options that were specified when it was opened When the operation is complete the asynchronous process notifies the initiating process using the method requested in the aiocb You can cancel a started operation or all pending operations for a given file descriptor using aio_cancel see the aio_cancel 3 reference page Assuring Data Integrity With sequential output you call fsync to ensure that all buffered data has been written However you cannot use fsyne with asynchronous I O since you are not sure when the write calls will execute The aio_fsync function queues the equivalent of an fsync call for asynchronous execution see the aio_fsync 3 reference page This function takes an aiocb The file d
99. is far smaller than the cost of communicating over a socket and a network link e Peripherals are accessible from any node but there is a time penalty for access to a peripheral from a node other than the one to which the peripheral is attached The implications of these features are explored at more length under Using Origin2000 Nonuniform Memory on page 29 Parallel Execution Models You can compare the available models for parallel programming on two features granularity The relative size of the unit of computation that executes in parallel a single statement a function or an entire process communication The basic mechanism by which the independent concurrent units channel of the program exchange data and synchronize their activity 247 Chapter 10 Models of Parallel Computation 248 A summary comparison of the available models is shown in Table 10 1 Table 10 1 Comparing Parallel Models Model Granularity Communication Power Fortran Looping statement DO or for Shared variables in a single user IRIS POWER C statement address space Ada95 tasks Ada Procedure Shared variables in a single user address space POSIX threads C function Shared variables in a single user address space Lightweight UNIX processes C function Arena memory segment in a sproc single user address space General UNIX processes Process Arena segment mapped to fork exec multiple address spaces Shared Memory SHME
100. is the normal setting when a memory arena is shared among multiple processes When a mapped segment is writable any changes to the segment in memory are also written to the file that is mapped The mapped file is the backing store for the segment When MAP_AUTOGROW is specified also a store beyond the end of the segment lengthens the segment and also the file to which it is mapped MAP_PRIVATE specifies that changes to shared pages are private to the process that makes the changes The pages of a private segment are shared on a copy on write basis there is only one copy as long as they are unmodified When the process that specifies MAP_PRIVATE stores into the segment that page is copied The process has a private copy of the modified page from then on The backing store for unmodified pages is the file while the backing store for modified pages is the system swap space When MAP_AUTOGROW is specified also a store beyond the end of the segment lengthens only the private copy of the segment the file is unchanged Mapping Segments of Memory The difference between MAP_SHARED and MAP_PRIVATE is important only when the segment can be modified When the prot argument does not include PROT_WRITE there is no question of modifying or extending the segment so the backing store is always the mapped object However the choice of MAP_SHARED or MAP_PRIVATE does affect how you lock the mapped segment into memory if you do see Locking P
101. localized size of the objects involved Most use some hints provided by the developer that can regulate this layout For example some IRIS IM widgets providing these services are XmForm XmPanedWindow and XmRowColumn Dynamic layout is probably the simplest way to prevent localization difficulties Note The IRIS IM product is the Silicon Graphics port of the OSF Motif product and should not be confused with IM the abbreviation for Input Methods Constant Layout Under certain circumstances an application may insist on having a predefined layout When this is so the application must provide objects that are constructed to allow localization A Quit button that just barely allows room for the Latin 1 string Quit is not likely to suffice when localizers attempt to fit their translations into that small space In order to enforce constant layout the developer incurs the heavy responsibility of making sure the objects are localizable This means a lot of investigation the there that ought to be enough approach is chancy at best Popular Encodings Popular Encodings Localized Layout Some toolkits provide for layout control by run time reading of strings or other data files Applications that use such toolkits can easily finesse the layout issue by providing the capability for localization of the layout as well as localization of the contents of the layout This provides each localizer maximum freedom in presentin
102. lock is available usunsetlock 3P Release a lock making it available for other processes uscsetlock 3P Seize a lock if it is available otherwise return a 1 uswsetlock 3P Seize a lock suspending the caller if necessary takes a specified number of spins as an argument ustestlock 3P Test a lock returning 0 if it is instantaneously available and 1 if it is not available Tip When reading the reference pages cited above notice that usnewlock returns a ulock_t object which is simply a pointer All the functions that operate on locks take a ulock_t object not a pointer to a ulock_t That is the ulock_t type represents a handle or reference to a lock not a lock itself This differs from the treatment of semaphores which is described under Creating Normal Semaphores on page 87 On uniprocessors none of the functions us c w setlock spin if the lock is available they return immediately and if it is not they suspend the calling process and give up the CPU On multiprocessors ussettlock spins for a default number of times before it suspends the process The function uswsetlock is the same but you can specify the number of spins to take before suspending A process can call usunsetlock on a lock that is either not locked or locked by another process In either case the lock is unlocked Double tripping calling a set lock function twice with the same lock is also permissible The caller blocks until anot
103. madvise 2 reference page you can tell IRIX that a range of pages is not needed by your process The pages remain defined in the address space so this is not a means of reducing the need for swap space However IRIX puts the pages at the top of its list of pages to be reclaimed when another process or the calling process suffers a page fault The madvise function is rarely needed by real time programs which are usually more concerned with keeping pages in memory than with letting them leave memory However there could be a use for it in special cases Using Origin2000 Nonuniform Memory In the Origin2000 systems which include the Origin200 and Onyx2 product lines physical memory is implemented using a cache coherent nonuniform memory architecture abbreviated CC NUMA or sometimes simply NUMA For almost all programs the CC NUMA hardware makes no difference at all The virtual address space as described in this chapter is implemented exactly the same in all versions of IRIX Your program cannot tell whether the memory hardware is bus based as ina CHALLENGE system or uses CC NUMA as in the Origin2000 except that in a heavily loaded multiprocessor your program will run faster in an Origin than in a CHALLENGE However when you implement a program that has critical performance requirements uses multithreading and needs a large memory space all three conditions must be present you may need to control the placement of virtual pa
104. memory segments are located next to specific CPUs About Multithreaded Memory Use IRIX supports parallel processing under several different models see Chapter 10 Models of Parallel Computation When a program uses multiple parallel threads of execution additional performance issues can arise e Cache contention can occur as multiple threads running in different CPUs invalidate each other s cached data e Default allocation policies can place memory segments in different nodes from the CPUs the threads that use the data e Default allocation to a single node when threads are running in many nodes can saturate the node with memory requests slowing access These issues are discussed in the following topics Dealing With Cache Contention When one CPU updates a cache line all other CPUs that refer to the same data must fetch a fresh copy When a line is used often from multiple CPUs and is also updated frequently the data is effectively not cached but accessed at memory speeds In addition when more than one CPU updates the same cache line the CPUs are forced to execute in turn Each waits until it can have exclusive ownership of the line When multiple CPUs update the same line concurrently the data is accessed at a fraction of memory speeds and all the CPUs are forced to idle for many cycles Using Origin2000 Nonuniform Memory An update of one 64 bit word invalidates the 15 other words in the same cache lin
105. message priority to use size_t msglen 64 message size int count 1 number of messages to send char msgptr gt allocated message space int c while 1 c getopt argc argv p b c n switch c case p priority msg_prio strtoul optarg NULL 0 break case b bytes msglen strtoul optarg NULL 0 if msglen lt 32 msglen 32 break case c count count strtoul optarg NULL 0 if count gt 99999 count 99999 break case n use nonblock oflags O_NONBLOCK break default unknown or missing argument return 1 if optind lt argc path argv optind else printf Queue pathname required n msgptr calloc 1l msglen mqd mq_open path oflags if 1 mqd char stime 26 const time_t tm void ctime_r stime 24 0O for c 1 c lt count time NULL amp tm stime FFE first non option argument return 1 current time value formatted time string drop annoying n 151 Chapter 6 Message Queues 152 sprintf msgptr 05d s c stime if mq_send mqd msgptr msglen msg_prio perror mq_send break else perror mq_open O_WRONLY Example of mq_receive The mq_receive program in Example 6 4 allows you to receive and display messages from a queue These command line arguments are accepted path The file pathn
106. might know that the daemon responsible for reading and writing pages from disk was called vhand and its activity could be monitored However starting with IRIX 6 4 all such system daemons became kernel threads and are no longer visible to commands such as ps or gr_top Read Only Pages A page of memory can be marked as valid for reading but invalid for writing Program text is marked this way because program text is read only it is never changed If a process attempts to modify a read only page a hardware interrupt occurs When the page is truly read only the kernel turns this into a SIGSEGV signal to the program Unless the program is handling this signal the result is to terminate the program witha segmentation fault Copy on Write Pages When fork is executed the new process shares the pages of the parent process under a rule of copy on write The pages in the new address space are marked read only When the new process attempts to modify a page a hardware interrupt occurs The kernel makes acopy of that page and changes the new address space to point to the copied page Then the process continues to execute modifying the page of which it now has a unique copy You can apply the copy on write discipline to the pages of an arena shared with other processes see Mapping a File for Shared Memory on page 19 Interrogating the Memory System Interrogating the Memory System You can get information about the state of
107. must be set before the file is opened a change has no effect on a file that is already open Example 7 9 shows a fragment of code that sets mandatory lock mode on a given filename Example 7 9 Setting Mandatory Locking Permission Bits include lt sys types h gt include lt sys stat h gt int setMandatoryLocking char filename int mode struct stat buf if stat filename amp buf lt 0 perror stat 2 return error mode buf st_mode ensure group execute permission 0010 bit is off mode amp S_IEXEC gt gt 3 turn on set group id bit in mode mode S_ISGID if chmod filename mode lt 0 perror chmod 2 return error return 0 When IRIX opens a file it checks to see whether both of two conditions are true e Set group ID bit is 1 e Group execute permission is 0 191 Chapter 7 File and Record Locking When both are true the file is marked for mandatory locking and each use of creat open read and write tests for contending locks Some points to remember about mandatory locking e Mandatory locking does not protect against file truncation with the truncate function see the truncate 2 reference page which does not look for locks on the truncated portion of the file e Mandatory locking protects only those portions of a file that are locked Other portions of the file that are not locked may be accessed according to normal UNIX
108. of available fonts by calling XListFonts or the function XListFontsWithInfo Viewing Fonts To see what a particular font looks like use the command xfd and specify a font name or font alias known to the X Window System by using the option fn For example to display the 14 point Adobe Courier Bold font enter xfd fn adobe courier bold r normal 14 140 75 75 m 90 is08859 1 To request a Utopia Regular font scaled to the size of 28 points enter xfd fn adobe utopia medium r normal 0 280 0 0 p 0 iso8859 1 You can use an asterisk to indicate that any value is acceptable for a part of an X font name However asterisks in a command must be protected from the shell with quotes For example enter xfd fn itc bookman demi i normal 11 80 100 100 p 63 iso8859 1 to indicate that xfd can use an ITC Bookman Demi Italic font from any foundry The xfd command displays all characters in a specified font as shown in Figure 15 2 Using Fonts With the X Window System Adobe Courier Bold R Normal 14 140 75 75 M 90 1IS808859 1 Select a character range 0x0000 0 0 thru Ox00ff 0 255 upper left 0x0000 0 0 Figure 15 2 Sample Display From xfd 317 Chapter 15 Working With Fonts 318 To open a shell window that uses a certain font enter xwsh fn font name Getting the Current X Font Path The X system locates font files along a path similar to the execution path used to find executab
109. opening 395 Over the Spot style 398 root window style 397 setting styles 399 status 397 Index strings 405 using styles 399 XFilterEvent 404 XLookupString 405 language information 364 languages Asian 411 412 in locale strings 343 Japanese 411 Latin library functions 360 localeconv 356 locale specific behavior 359 locales See locales message catalogs 372 MNLS fmtmsg 379 message catalogs See message catalogs MNLS pfmt 378 monetary formats 355 Motif 390 multibyte characters about converting 350 size of 350 string length 351 using 349 multilingual support 345 native language support 362 numerical formats 355 pfmt 378 printf 356 381 regular expressions 359 360 365 regular expressions examples 367 setlocal 342 setting locale 340 shift tables 364 signed chars 348 sorting rules 354 standards 337 strings 372 territories 343 time formats 357 Unicode 413 user input 391 application programming 391 text objects 391 toolkit text object 391 wide characters about 348 converting 353 XFontSetExtents 388 XPG 3 message catalogs See message catalogs regular expressions 359 X Window System about 383 changes 383 character sets 384 EUC encoding 386 fontsets 386 keyboard support 393 394 limitations 383 resource names 385 string resources 407 vertical text 384 XFontSetExtents 388 Xlib changes 384 Inter Process Communication See IPC
110. page 346 discusses codesets and encodings e modifiers are not actually part of the locale name definition they give more specific information about the desired localized behavior of an application For example under X11R5 or X11R6 a user can select an input method with modifiers To use the xwnmo Input Method server provided by Silicon Graphics for example add im _XWNMO to the locale string No standards exist for this part of a locale string Language data is implementation specific databases for the language en English might contain British cultural data in England and American cultural data in the United States If other than the default settings are required the territory field may be used For example the above cases could be more strictly defined by setting LANG to en_GB or en_US Full rigor might lead to en_GB ISO 8859 1 for England and en_US ISO 8859 1 for the USA ANSI C has defined a special locale value of C The C locale is guaranteed to work on all compliant systems and provides the user with the system s default locale This default is typically American English and ASCII but need not be POSIX has also defined a special locale value POSIX which is identical to the C locale The length of the locale string may not exceed NL_LLANGMAxX characters NL_LANGMAx is defined in usr include limits h However XPG 4 recommends that this string not counting modifiers not exceed 14 characters Using Locales Limitat
111. page for details 379 Chapter 16 Internationalizing Your Application 380 Internationalizing File Typing Rule Strings With MNLS You can internationalize the strings defined in the LEGEND and MENUCMD rules in the File Typing Rule FTR file To internationalize these rules precede the string with the following catalogname msgnumber catalogname is optional and should be a valid MNLS catalog msgnumber is the line number in catalogname If you omit catalogname the uxsgidesktop catalog is used by default You can use these rules to create your own FTR catalog For example an entry looks like this LEGEND mycatalog 7 Archive 8mm Tape Drive This entry uses line 7 from the catalog mycatalog as the LEGEND for this FTR If mycatalog is not available or line 7 is not accessible from mycatalog Archive 8mm Tape Drive is used as the LEGEND LEGEND 7 Archive 8mm Tape Drive This entry uses line 7 from the uxsgidesktop catalog if available Otherwise Archive 8mm Tape Drive is used The next example MENUCMD mycatalog 9 Eject Tape usr sbin eject dev tap displays line 9 from mycatalog if available Otherwise Eject Tape is displayed on the menu that pops up when you click an icon that uses this FTR You can internationalize strings in the command part of MENUCMD and CMD rules by using gettxt or any other convenient policy detailed in this section For
112. particular language assertion such as e upper case alphabetic character e lower case alphabetic character e punctuation character e control character e space character 363 Chapter 16 Internationalizing Your Application 364 Shift Tables Shift tables contain the corresponding upper and lower case combinations for each character defined in a coded character set Thus the upshifted or downshifted value of a character can be determined by accessing the relevant character entry in the shift table Language Information Language information or anginfo contains message text specific to a particular localization The library function nl_langinfo provides a procedural interface to this data allowing applications to discover cultural and language specific information at run time Individual items of langinfo data are identified by constants in Volume 2 XSI System Interfaces and Headers lt langinfo h gt Information specific to a culture or language includes the following Date and time formats Days of the week and months of the year Abbreviated names of days and months Radix character Separator for thousands Affirmative and negative responses to yes no questions Currency symbol and its position within a currency value Locale Specific Behavior Using Regular Expressions Regular expression are used widely throughout the services and are powerful mechanisms for locating and manipulating patterns in text I
113. process from truncating the file and so causing SIGBUS exceptions The one sure way to block changes to the file is to install a mandatory file lock You place a file lock with the lockf function see Chapter 7 File and Record Locking However a file lock is normally advisory that is it is effective only when every process that uses the file also calls lockf before changing it Mapping Segments of Memory You create a mandatory file lock by changing the protection mode of the file using the chmod function to set the mandatory file lock protection bit see the chmod 2 reference page When this is done a lock placed with lockf is recognized and enforced by open Mapping a File for Shared Memory You can use mmap simply to create a segment of memory that can be shared among unrelated processes e Inone process create a file or a POSIX shared memory object to represent the segment Typically a file is located in var tmp but it can be anywhere The permissions on the file or POSIX object determine the access permitted to other processes e Map the file or POSIX object into memory with mmap initialize the segment contents by writing into it e Inanother process get a file descriptor using open or the POSIX function shm_open specifying the same pathname e In that other process use mmap specifying the file descriptor of the file After this procedure both processes are using the identica
114. support provided by X11 Release 6 including features from X11R5 Internationalization Support in Motif points to information describing how to internationalize a Motif application Translating User Input discusses the translation of keyboard events into programmatic character strings for a variety of keyboards 333 Chapter 16 Internationalizing Your Application e GUI Concerns discusses internationalizing applications that use graphical user interfaces GUIs e Popular Encodings presents some common non ASCII encodings For a list of ISO 3166 country names and abbreviations see Appendix A ISO 3166 Country Names and Abbreviations You can find detailed information about fonts in Chapter 15 Working With Fonts Also you can find additional information about internationalizing an application in the IRIX Interactive Desktop Integration Guide Overview of Internationalization 334 Internationalized software can be made to produce output in a user s native language to format data such as dates and currency values according to the user s local customs and to otherwise make the software easier to use for users from a culture other than that of the original software developer As computers become more widely used in non American cultures it becomes increasingly important that developers stop relying on the conventions of American programming and the English language in their programs This
115. swap disk space to be allocated Addresses are reserved with brk or malloc but they are only defined and allocated in swap when your program references them When IRIX uses delayed definition virtual swap it has the following effects A program cannot find the limits of swap space using malloc it never returns NULL until the program exceeds its resource limit regardless of available swap Instead when a program finally accesses a new page of allocated space and there is at that time no room in the swap partition the program receives a SIGKILL signal A large memory allocation by one program cannot monopolize the swap disk until the program actually uses the allocated memory if it ever does Much less swap space is required for a successful fork call You can test whether the system uses virtual swap with the chkconfig command as described in the chkconfig 1 reference page chkconfig vswap echo S status 0 As you write a new program assume that virtual swap may be used Do not allocate memory merely to find out if you can Allocate no more memory than your program needs and use the memory immediately after allocating it Defining the Address Space If you are porting a program written for a conventional UNIX system you might discover that it tests the limits of allocatable memory by calling malloc until malloc returns a NULL and then does not use the memory In this case you have several choices
116. that is the compiled files containing the collation information monetary information and so on are located in usr lib locale lt locale gt lt category gt where lt locale gt and lt category gt are the names of the locale and category respectively For example the database for the LC_COLLATE category of the French locale fr would be in usr lib locale fr LC_COLLATE There will probably be multiple locales symbolically linked to each other usually in cases where a specific locale name points to the more general case For example usr libflocale POSIX might point to usr libflocale C Locale Naming Conventions A locale string is of the form language _territory encoding modifier where e language is the two letter ISO 639 abbreviation for the language name e territory is the two uppercase letter ISO 3166 abbreviation for the territory name For a list of these abbreviations see the table in Appendix A ISO 3166 Country Names and Abbreviations 343 Chapter 16 Internationalizing Your Application 344 e encoding is the name of the character encoding mapping between numbers and characters For western languages this is typically the codeset such as 8859 1 or ASCII For Asian languages where an encoding may encode multiple codesets the encodings themselves have names such as UJIS or EUC these encodings are described later in this section Character Sets Codesets and Encodings on
117. the int Character Representation Western languages usually require only one byte for each character Asian languages however often require two or even four bytes per character and some Asian encodings allow a variable number of bytes per character The two kinds of encodings that allow more than one byte per character are e multibyte MB characters are of variable size e wide characters WC or wchar characters are a fixed number of bytes long Character Sets Codesets and Encodings The application developer must decide where to use WC and MB characters and strings e Multibyte strings are almost the default string I O uses MB MB code works for ASCII and ISO 8859 and MB characters use less space than do wide characters However manipulating individual characters within a multibyte string is difficult Note Traditional strings are merely a special case of multibyte strings where every character happens to be one byte long and there is only one codeset All MB code including conversion to and from wchars works for traditional ASCII or ISO 8859 strings e Applications that do heavy string manipulation typically use WC strings for such activity because manipulating individual WC characters in a string is much simpler than doing the same thing with MB characters So wide characters are used as necessary to provide programming ease or runtime speed however they take up more space than MB characters Note WC is system
118. the lock It uses this exclusive control to increment the count of processes using the arena When usgetinfo returns 0 the calling process is probably the first to create the arena so it allocates an arenaStuff structure and also allocates the essential lock and puts it in a locked state Then it calls uscasinfo to swap the arenaStuff address for the expected value of 0 When the swap succeeds the process completes initializing the arena and releases the lock 69 Chapter 3 Sharing Memory Between Processes 70 The call to uscasinfo could fail if between the time the process receives a 0 from usgetinfo and the time it calls uscasinfo another process executes this same code and installs its own arenaStuff The process handles this unusual event by releasing the items it allocated and repeating the whole process When unrelated processes join an arena with code like that shown in Example 3 3 they should terminate their use of the arena with code similar to Example 3 4 Example 3 4 Resigning From an Arena The following function reverses the operation of joinArena Even if the calling process is the last one to hold the arena nothing drastic is done This is because it is impossible to perform usinit usgetinfo ussetlock as an atomic sequence Once an arena comes into being it must remain usable until the entire application shuts down Unlinking the arena file can be the last thing that main does
119. the lock actually is and which process owns the lock Example 7 8 shows a code fragment that uses lockf to test for a lock on a file Example 7 8 Testing for Contending Lock Using lockf find a blocked record seek to beginning of file void lseek fd 0 OL set the size of the test region to zero to test until the end of the file address space if lockf fd F_TEST OL lt 0 switch errno case EACCES case EAGAIN void printf file is locked by another process n break case EBADF bad argument passed to lockf perror lockf break default void printf lockf unknown error lt d gt n errno break When a process forks the child receives a copy of the file descriptors that the parent has opened The parent and child also share a common file pointer for each file If the parent seeks to a point in the file the child s file pointer is also set to that location Similarly when a share group of processes is created using sproc and the sproc flag PR_SFDS is used to keep the open file table synchronized for all processes see the sproc 2 reference page then there is a single file pointer for each file and it is shared by every process in the share group This feature has important implications when using record locking The current value of the file pointer is used as the reference for the offset of the beginning of the lock in lockf at all times and
120. to Demonstrate mq_getattr and mq_setattr Ay include include include include Program to test mq getattr 3 displaying queue information mq_attr lt path gt lt path gt pathname of the queue which must exist lt mqueue h gt message queue stuff lt errno h gt errno and perror lt fentl h gt O RDONLY lt stdio h gt int main int argc char argv mqd_t mqd queue descriptor struct mq_attr obuf output attr struct for getattr if argc lt 2 printf A pathname of a message queue is required n return 1 mqd mq_open argv 1 O_RDONLY if 1 mqd if mq_getattr mqd amp obuf printf flags Ox x maxmsg d msgsize d curmsgs d n obuf mq_flags obuf mq_maxmsg obuf mq_msgsize obuf mq_curmsgs else else perror mq_getattr perror mq_open POSIX Message Queues Example of mq_open The program mq_open in Example 6 2 allows you to create a message queue from the command line The following command line arguments are supported path p perms b bytes m msgs C X The file pathname of the queue must be given following all options Access permissions to set for example p 0664 The maximum message size this queue allows for example b 256 The maximum number of messages that can be pending on this queue for example m 64 Use the O_CREAT
121. value of one semaphores Any process having write access Examples of some of these uses can be seen under Example Uses of semctl for Query on page 106 Caution Some operations of the semctl function use only three arguments but some operations require a fourth argument see reference page semctl 2 for details When passing a fourth argument to semctl it is extremely important that you pass a union semun as specified in the reference page You might look at the contents of the union and think that since all its fields are addresses there is no effective difference between passing a union and passing a plain address of a buffer or array However if your program is compiled with the n32 or 64 options the alignment of the two kinds of arguments is different Always pass an address as shown in the example programs in this chapter union semun arg4 arg4 buffer amp ds_buffer semctl a b c arg4 If your program passes only the address as in semctl a b c amp ds_buffer the code will not work correctly when compiled n32 or 64 99 Chapter 4 Mutual Exclusion 100 Using Semaphore Sets You perform operations on the semaphores in a set by calling semop This function takes a semaphore set ID and an array of one or more semaphore operation structures Each of the operation structures specifies the following e The index of a semaphore in the set numbering the semaphores from 0 e Anumber s
122. 048 ES 10 DO_SPROCS 1 QUITIFNULL PTR MSG QUITIFMONE INT MSG s the Caveats section of sproc 2 for clock for perror for printf for getenv malloc 3c usinit amp friends for bzero for pretl get setrlimit for pretl required by lseek pretl ditto wanted by sproc ditto for signals gets sys signal and sys siginfo async I O input units play with this number max sprocs anything from 4 to 20 or so set 0 to do all I O in a single process if NULL PTR perror MSG return errno if 1 INT perror MSG return errno BORK KK KR RR RR RRR A RR AR RAR RR AAA A AAA A A A A A A A Ok The following structure contains the info needed by one child proc The main program builds an array of MAX_INFILES of these The reason for storing the actual filename here not a pointer is to force the struct to gt 128 bytes Then when the procs run in different CPUs on a CHALLENGE the info structs will be in different lines and a store by one proc will not invalidate a cache line input filename from argv n FD for this file buffer for this file process ID of child process size of this input file semaphore used by methods 2 amp 3 starting offset in output file current offset in input file sum of utime stime to read file aiocb used for reading
123. 2xlfd_map for the Utopia fonts are Utopia Bold adobe utopia bold r normal 0 0 0 0 p 0 1is08859 1 Utopia BoldItalic adobe utopia bold i normal 0 0 0 0 p 0 is08859 1 Utopia Italic adobe utopia medium i normal 0 0 0 0 p 0 is08859 1 Utopia Regular adobe utopia medium r normal 0 0 0 0 p 0 1is08859 1 The first field is the PostScript font name as specified in the outline font file see Adding an Outline Font on page 326 The second field is the X 14 part font name with 0 for all specific dimension values When you add your own bitmap or outline fonts put their entries in a file called usr lib X11 fonts ps2xlfd_map local That way your entries do not disappear when you upgrade your system software Make sure that there is no overlap between your entries and the entries in other ps2xlfd_map files If you want to establish alias names for any of the new fonts create or edit fonts alias files in the appropriate directories see Creating Font Aliases on page 321 Installing and Adding Font and Font Metric Files 7 Invoke the mkfontdir command to rebuild the fonts dir database in each directory where you added bitmap files Enter the command mkfontdir usr 1ibX11 fonts dpi 10 to create a new fonts dir fonts directory file in the 100dpi and 75dpi directories Use the xset command to notify the window system to rebuild its list of fonts xset fp rehash To check wh
124. 3 Reading an XPG 4 Catalog include lt stdio h gt include lt locale h gt include lt nl_types h gt define SET1 1 define WRLD_MSG 1 int main nl_catd msgd char message setlocale LC_ALL msgd catopen hw 0 message catgets msgd SET1 WRLD_MSG Hello world n printf message catclose msgd 373 Chapter 16 Internationalizing Your Application 374 The previous example uses printf instead of puts in order to make a point the format string of printf came from a catalog Note the crucial difference between these two statements printf catgets msgd set num defaultStr printf ss catgets msgd set num defaultStr In the first statement the catalog provides the printf formatting string possibly containing conversion specifications and escape sequences In the second statement the string from the catalog is treated as data and not interpreted for conversion specifications For further discussion of issues relating to this important distinction see NVariably Ordered Referencing of printf Arguments XPG 4 Catalog Location XPG 4 message catalogs are located using the environment variable NLSPATH The default NLSPATH is usr lib locale Y L LC_MESSAGES N where L is filled in by the LANG environment variable and N is filled in by the name argument to catopen NLSPATH can specify multiple pathnames in ordered precedence much like the PATH variable The f
125. 4 Reserved by the POSIX standard for system use Reserved by POSIX for real time programming Signals with smaller numbers have priority for delivery The low numbered BSD compatible signals which include all kernel produced signals are delivered ahead of real time signals and signal 49 takes precedence over signal 64 Table 5 1 is reproduced from the signal 5 reference page for convenience Table 5 1 Signal Numbers and Default Actions Symbolic Numeric Name Value Default Action Normal Meaning SIGHUP 1 Terminate Controlling terminal disconnect see termio 7 SIGINT 2 Terminate Interrupt key signal from controlling terminal see termio 7 SIGQUIT 3 Terminate and dump Quit key signal from controlling terminal see termio 7 SIGILL 4 Terminate and dump Attempt to execute illegal instruction SIGTRAP 5 Terminate and dump Trace breakpoint reached see proc 4 SIGABRT 6 Terminate and dump Abort SIGEMT 7 Terminate and dump Emulation trap SIGFPE 8 Terminate and dump Arithmetic exception see math 3M sigfpe 3C and matherr 3M SIGKILL 9 Terminate Kill request from software or user SIGBUS 10 Terminate and dump Bus error hardware exception SIGSEGV 11 Terminate and dump Segmentation fault illegal address Signals Table 5 1 Signal Numbers and Default Actions continued Symbolic Numeric Name Value Default Action Normal Meaning SIGSYS 12 Terminate and dump Invalid system call SIGPIPE 13 Terminate
126. 4 shared memory are discussed in the following topics and summarized in Table 3 6 Table 3 6 SVR4 Shared Memory Functions Function Name Purpose and Operation shmget 2 Create a shared memory IPC object or return the ID of one shmctl 2 Get the status of a shared memory segment change permissions or user IDs or lock or unlock a segment in memory shmat 2 Attach a shared memory segment to the address space shmdt 2 Detach a shared memory segment from the address space Creating or Finding a Shared Memory Segment A process creates a shared memory segment or locates an existing segment using the shmget system function When it creates a segment the arguments to this function establish e The numeric key of the segment e The size of the segment e The user ID and group ID of the segment creator and owner e The access permissions to the segment When the function locates an existing segment access to the segment is controlled by the access permissions and by the user ID and group ID of the calling process 71 Chapter 3 Sharing Memory Between Processes 72 Unlike an IRIX shared arena a shared segment does not grow automatically as it is used The size specified when it is created is fixed The shared segment is initialized to binary zero As implemented in IRIX the pages of the segment are created as they are first referenced see Mapping a Segment of Zeros on page 19 The value returned by shmget
127. 6 includes the definition of the X Portable Character Set which is required to exist in all locales supported by Xlib There is no encoding defined for this set it is only a character set The set which is similar to printable ASCII plus the newline and tab consists of these characters abcdefghijklmnogrstuvwxyz ABCDEFGHIJKLMNOPORS TUVWXYZ 0123456789 IUESSEl 27 lt gt 7 1 gt lt space gt lt tab gt lt newline gt The Host Portable Character Encoding is the encoding of the X Portable Character Set on the Xlib host This encoding is part of X and is thus independent of locale the coding remains the same for all locales supported by the host Strings used or returned by Xlib routines are either in the Host Portable Character Encoding or a locale specific encoding The Xlib reference pages specify which encodings are used where Some string constructs such as TextProperty contain information regarding their own encoding Xlib Interface Change Full use of X11R6 s internationalization features means calling some new routines supplied in the X11R6 Xlib While all old Xlib applications work with the new Xlib developers should change their code in places These are described below Internationalization Support in X11R6 Resource Names Resource names are compiled into programs Because of that their encoding must be known independent of locale Trying to add a level of indirection here results in a p
128. 7 Index file and record locking 175 194 across systems 192 deadlocks 190 efficiency comparative 192 F_GETLK 187 F_SETLK 185 F_TEST 189 F_ULOCK 187 F_UNLCK 187 failure 184 file permissions and 178 forking 190 lock information 187 locking a file 180 mandatore 190 multiple read locks 187 NFS with 192 opening files 179 order of lock removal 187 overview 176 178 removing locks 183 setting locks 183 file descriptor with asynchronous I O 198 with mmap 13 file typing rules 380 LEGEND 380 MENUCMD 380 Finland country code 416 fonts 309 330 accessing 314 adding 319 329 bitmap font 322 325 font files 322 font metric file 328 329 outline font 326 328 Utopia Regular font files 322 aliases 315 character defined 311 display characters 316 downloading 329 images 312 installing 319 329 missing fonts 329 names 313 315 opening a shell window 318 path 318 pixels 312 point size 312 PostScript printers 329 programming access 314 resolution and size 312 scaling 316 Speedo format 319 Type 1 font 319 329 330 typeface defined 311 using APIs 314 Utopia fonts 329 viewing 316 virtual memory 330 xfd command 316 X Window System 313 315 329 fontsets 386 387 creating 387 specifying 386 using 387 fork defines address space 5 new address space copy on write 10 forking 190 France country code 416 fsync 196 ftruncate on memory mapped file
129. Attributes 61 Creating an Arena 63 Joining an Arena 63 Restricting Access to an Arena 64 Arena Access From Processes in a Share Group 64 Allocating in an Arena 65 Exchanging the First Datum 66 System V Shared Memory Functions 71 Creating or Finding a Shared Memory Segment 71 Attaching a Shared Segment 72 Managing a Shared Segment 72 Information About Shared Memory 73 Shared Memory Examples 73 Example of Creating a Shared Segment 73 Example of Attaching a Shared Segment 74 vii Contents viii Mutual Exclusion 77 Overview of Mutual Exclusion 78 Test and Set Instructions 78 Locks 79 Semaphores 80 Condition Variables 81 Barriers 82 POSIX Facilities for Mutual Exclusion 82 Managing Unnamed Semaphores_ 83 Managing Named Semaphores 84 Creating a Named Semaphore 84 Closing and Removing a Named Semaphore 85 Using Semaphores 85 Using Mutexes and Condition Variables 86 IRIX Facilities for Mutual Exclusion 87 Using IRIX Semaphores 87 Creating Normal Semaphores 87 Creating Polled Semaphores 88 Operating on Semaphores 89 Using Locks 90 Creating and Managing Locks 90 Claiming and Releasing Locks 91 Using Barriers 92 Using Test and Set Functions 92 Using Test and Set 93 Using Compare and Swap 93 Using Compiler Intrinsics for Test and Set 95 Creating or Finding a Semaphore Set 97 Managing Semaphore Sets 98 Using Semaphore Sets 100 Example Programs 101 Example Uses of semget 102 Example Uses of semctl for Management 104 Contents
130. BJ Bermuda BM Bhutan BT Bolivia BO Botswana BW Bouvet Island BV Brazil BR British Indian IO Ocean Territory Brunei BN Bulgaria BG Burkina Faso BF Darussalam Burma BU Burundi BI Byelorussia BY Cameroon CM Canada CA Cape Verde CV Cayman Islands KY Central African CF Chad TD Republic Chile CL China CN Christmas Island CX Cocos Islands CC Colombia CO Comoros KM 415 Appendix A ISO 3166 Country Names and Abbreviations 416 Table A 1 ISO 3166 Country Codes continued Country Name Code Country Name Code Country Name Code Congo CG Cook Islands CK Costa Rica CR Cote D Ivoire CI Cuba CU Cyprus CY Czech Republic CS Denmark DK Djibouti DJ Dominica DM Dominican DO East Timor TP Republic Ecuador EC Egypt EG El Salvador SV Equatorial GQ Ethiopia ET Falkland Islands FK Guinea Faroe Islands FO Fiji FJ Finland FI France FR French Guiana GF French Polynesia PF French Southern TF Gabon GA Gambia GM Territories Germany DE Ghana GH Gibraltar GI Greece GR Greenland GL Grenada GD Guadalupe GP Guam GU Guatemala GT Guinea GN Guinea Bissau GW Guyana GY Haiti HT Heard and HM Honduras HN McDonald Islands Hong Kong HK Hungary HU Iceland IS India IN Indonesia ID Iran IR Iraq IQ Ireland IE Israel IL Italy IT Jamaica JM Japan JP Jordan JO Kampuchea KH Kenya KE Kiribati KI Korea KPor Kuwait KW KR Table A 1 ISO 3166 Country Codes continued Country Name Code Country Name Code Country Name Cod
131. BSD Functions for Interval Timers Function Name Purpose and Operation setitimer 2 Set the expiration and repeat interval of a timer getitimer 2 Return the current value of a timer Timer Facilities Each process has three itimers available to it as summarized in Table 5 11 Table 5 11 Types of itimer Kind of itimer Interval Measured Resolution Signal Sent ITIMER_ REAL Elapsed clock time 1 millisecond or less SIGALRM ITIMER_VIRTUAL User time process 1 second SIGVTALRM execution time ITIMER_PROF User system time 1 second SIGPROF The ITIMER_VIRTUAL and ITIMER_PROF have a relatively coarse precision Their intervals vary depending on when and how often the process is dispatched The ITIMER_REAL timer is comparable to the POSIX time base CLOCK_SGI_FAST In order to use an itimer you establish a signal handler for the appropriate signal as shown in Table 5 11 then issue the setitimer call The principal argument to this function is a struct itimerval an object containing two incremental time values The it_value field specifies the time until the timer should expire The it_interval field when nonzero gives the time that should be loaded into the timer after it expires Tip One excellent reason not to mix BSD and POSIX timer support in the same program is that the POSIX struct itimerspec used to set a POSIX timer and the BSD struct itermval used to set a BSD itimer have fields with identical names but the
132. C_COLLATE Regular expressions strcoll and strxfrm LC_CTYPE Regular expressions and ctype routines such as islower LC_MESSAGES gettxt pfmt and nl_langinfo LC_MONETARY _localeconv and strfmon LC_NUMERIC Decimal point character for formatted I O and nonmonetary formatting information returned by localeconv LC_TIME ascftime cftime getdate and strftime Categories correspond to databases that contain relevant information for each defined locale The locations of these databases are given in the Location of Locale Specific Data on page 343 341 Chapter 16 Internationalizing Your Application 342 Setting the Locale The setlocale function attempts to set the locale of the specified category to the specified locale You should almost always pass the empty string as the locale parameter to conform to user preferences On success setlocale returns the new value of the category If setlocale couldn t set the category to the value requested it returns NULL and does not change locale Empty String An empty string passed as the locale parameter is special It specifies that the locale should be chosen based on environment variables This is the way a user specifies a preferred locale and that preference should almost always be honored The variables are checked hierarchically depending on category as shown in Table 16 2 for instance if the category is LC_COLLATE an empty string loca
133. ES break mission impossible sginap 1 let lock holder run return errno The following points should be noted in Example 7 2 e Because fentl supports both read and write locks the type of the lock F_WRLCK is specified in the _type e The operation code F_SETLK is used to request that the function return if it cannot place the lock The code F_SETLKW would request that the function suspend until the lock can be placed e The starting location of the record is the sum of two fields _whence and I_start Both must be set to 0 in order to get the starting point to the beginning of the file 181 Chapter 7 File and Record Locking 182 Whole File Lock With lockf Example 7 3 shows a version of the lockWholeFile function that uses lockf Like fentl lockf treats a record length of 0 as meaning to end of file Example 7 3 Setting a Whole File Lock With lockf include lt unistd h gt for F_TLOCK include lt fcntl h gt for O_RDWR include lt errno h gt for EAGAIN define MAX_TRY 10 int lockWholeFile int fd int tries int limit tries tries MAX_TRY int try lseek fd 0L SEEK_SET set start of lock range for try 0 try lt limit try if 0 lockf fd F_TLOCK OL break mission accomplished if errno EAGAIN break mission impossible sginap 1 let lock holder run
134. I Translating User Input Input Methods IMs Input methods IMs are ways to translate keyboard input events into text strings You would use a different input method for instance to type on a USA keyboard in Chinese than to type on the same keyboard in English Nobody would build a keyboard suitable for direct input of the tens of thousands of distinct Chinese characters IMs come in two flavors front end and back end Both types can use identical application programming interfaces so you lose no generality by using back end methods for our examples here To use an IM follow these steps 1 Open the IM 2 Find out what the IM can do 3 Agree upon capabilities to use 4 Create input contexts with preferences and window s specified see Input Contexts ICs on page 400 5 Set the input context focus 6 Process events Although all applications go through the same setup when establishing input methods the results can vary widely In a Japanese locale you might end up with networked communications with an input method server and a kanji translation server with circuitous paths for Key events But in a Swiss locale for example it is likely that nothing would occur besides a flag or two being set in Xlib Since operating in non Asian locales ends up bypassing almost all of the things that might make input methods expensive Western users are not noticeably penalized for using Asia ready applications Opening
135. IO_NONE The mutex has no effect on the thread that acquires it This is the default PTHREAD_PRIO_PROTECT The thread holding the mutex runs at a priority at least as high as the highest priority of any mutex that it currently holds PTHREAD_PRIO_INHERIT The thread holding the mutex runs at a priority at least as high as the highest priority of any thread blocked on that mutex If a thread acquires a mutex and then is suspended for example because its time slice is up other threads can be blocked waiting for the mutex The PTHREAD_PRIO_PROTECT protocol prevents this Using pthread_mutexattr_setprioceiling you set a priority higher than normal for the mutex A thread that acquires the mutex runs at this higher priority while it holds the mutex Another problem is that when a low priority thread has acquired a mutex and a thread with higher priority claims the mutex and is blocked a priority inversion takes place a higher priority thread is forced to wait for one of lower priority The PTHREAD_PRIO_INHERIT protocol prevents this when a thread of higher priority blocks the thread holding the mutex has its priority boosted during the time it holds the mutex Tip PTHREAD_PRIO_NONE uses a faster code path than the other two priority options for mutexes By default only threads within a process share a mutex Using pthread_mutexattr_setpshared you can allow any thread from any process with access to the mutex memory locat
136. IPC functions for code that must comply with the MIPS ABI or code that you are porting from another System V operating system 47 Chapter 2 Interprocess Communication Using POSIX IPC 48 In order to use the POSIX IPC functions described in this part of the book you must include the correct header files and libraries when compiling The header files required for each function are listed in the reference pages for the functions POSIX IPC functions are defined in the standard libc library That library is included automatically in any link by the cc command POSIX IPC Name Space POSIX shared memory segments named semaphores and message queues are persistent objects that survive the termination of the program that creates them unless the program explicitly removes them The POSIX standard specifies that these persistent names can be implemented in the filesystem and the current IRIX implementation does use filenames in the filesystem to represent IPC objects In order to access a named semaphore or message queue a program opens the object using a pathname similar to the way a program opens a disk file Because these persistent objects are currently implemented as files you can display and access them using IRIX commands for files such as ls rm chmod and chown However you should keep in mind that this is an implementation choice not a standardized behavior Other implementations of POSIX IPC may not use the filesystem a
137. LOCK flag with mq_open The count argument is limited to 99 999 so that the message text will not exceed 32 bytes the arbitrary minimum message size the program defines 149 Chapter 6 Message Queues 150 Example 6 3 Program to Demonstrate mq_send p lt priority gt b lt bytes gt c lt count gt n lt path gt aA include lt mqueue h gt include lt unistd h gt include lt errno h gt include lt time h gt include lt fcntl h gt include lt stdlib h gt include lt stdio h gt Program to test mq_send 3 mq_send p lt priority gt b lt bytes gt c lt count gt n lt path gt priority code to use default 0 size of the message default 64 min 32 number of messages to send default 1 max 9999 use O_NONBLOCK flag in open path to queue required The program sends lt count gt messages of lt bytes gt each at lt priority gt Each message is an ASCII string containing the time and date and a serial number 1 lt count gt The minimum message is 32 bytes message queue stuff for getopt errno and perror time 2 and ctime_r 3 O_WRONLY calloc 3 int main int argc char argv POSIX Message Queues char path gt first non option argument int oflags O_WRONLY open flags O_NONBLOCK may be added mqd_t mad queue descriptor from mq_open unsigned int msg_prio 0
138. M Process Memory copy Parallel Virtual Machine Process Memory copy within node PVM HIPPI network between nodes Message Passing MPI Process Memory copy within node special HIPPI Bypass interface between nodes Process Level Parallelism A UNIX process consists of an address space a large set of process state values and one thread of execution The main task of the IRIX kernel is to create processes and to dispatch them to different CPUs to maximize the utilization of the system IRIX contains a variety of interprocess communication IPC mechanisms which are discussed in Chapter 2 Interprocess Communication These mechanisms can be used to exchange data and to coordinate the activities of multiple asynchronous processes within a single memory system Processes running in different nodes of an Array must use one of the distributed models see Message Passing Models on page 251 Parallel Execution Models In traditional UNIX practice one process creates another with the system call fork which makes a duplicate of the calling process after which the two copies execute in parallel Typically the new process immediately uses the exec function to load a new program The fork 2 reference page contains a complete list of the state values that are duplicated when a process is created The exec 2 reference page details the process of creating a new program image for execution IRIX also supports the system
139. M library has been used for some time on Cray systems and is now available for all Silicon Graphics multiprocessors as part of the MPT A program built on SHMEM is a process level parallel program Each process runs in a separate address space The SHMEM library routines are used to exchange data and to coordinate execution between the processes SHMEM routines support remote data transfer through put operations which transfer data to a different process and get operations which transfer data from a different process Other operations supported include data broadcast and data reduction barrier synchronization as well as atomic memory updates such as a fetch and increment on remote or local data objects SHMEM operations are all memory to memory and as a result have extremely high bandwidth and low latency However a SHMEM based program cannot be distributed across multiple systems Parallel Execution Models Message Passing Interface MPI Model MPl is a standard programming interface for the construction of a portable parallel application in Fortran 77 or in C especially when the application can be decomposed into a fixed number of processes operating in a fixed topology for example a pipeline grid or tree MPI has wide use on many large computers A highly tuned efficient implementation of MPI is part of the MPT Within a single system MPI messages are moved memory to memory Between nodes of an Silicon Graphics Array sys
140. O is permitted on a device managed by XFS A real time guarantee can only be supported on the real time subvolume of a logical volume created by XLV The real time subvolume differs from the more common data subvolume in that it contains only data no file system management data such as directories or inodes The real time subvolume of an XLV volume can span multiple disk partitions and can be striped 237 Chapter 9 High Performance File I O 238 In addition the predictive failure analysis feature and the thermal recalibration feature of the drive firmware must be disabled as these can make device access times unpredictable For other requirements see IRIX Admin Disks and Filesystems and the grio 5 reference page Creating a Real time File You can only request a hard guaranteed rate against a real time disk file A real time disk file is identified by the fact that it is stored within the real time subvolume of an XFS logical volume The file management information for all files in a volume the directories as well as XFS management records are stored in the data subvolume A real time subvolume contains only the data of real time files A real time subvolume comprises an entire disk device or partition and uses a separate SCSI controller from the data subvolume Because of these constraints the GRIO facility can predict the data rate at which it can transfer the data of a real time file You create a real time file in the follow
141. OSIX Message Queues 140 The POSIX real time extensions detailed in IEEE standard 1003 1b include support for messages queues These functions are discussed in the following topics and demonstrated in example programs POSIX Message Queues Managing Message Queues The POSIX functions for creating controlling closing and removing message queues are summarized in Table 6 2 Table 6 2 POSIX Functions for Managing Message Queues Function Name Purpose and Operation mq_open 3 Create a queue if it does not exist and gain access to it mq_getattr 3 Get information about an open message queue mq_setattr 3 Change the blocking nonblocking attribute of an open message queue mq_close 3 Give up access to a queue mq_unlink 3 Remove a message queue from the system when the last process to have it open closes it Creating a Message Queue The mq_open function has two purposes It is used to gain access to a queue that exists and it can create a queue that does not exist To create a new queue call mq_open with four arguments as follows using the names given in the reference page mq_name The pathname that the queue will have oflag A set of flags that includes O_CREAT and may include O_EXCL mode The access permissions the queue will have mq_attr Either NULL or the address of an mq_attr structure specifying the queue attributes of maximum message size and maximum messages The name of a queue has the sa
142. RIS Development Foundation feature When the books are installed or mounted on your workstation use the command iiv or double click the IRIS InSight icon to launch IRIS Insight Then select the book you want from the bookshelf display When the manuals are not accessible to your workstation you can examine or order any Silicon Graphics manual on the World Wide Web using the following URL http techpubs sgi com Conventions Used in This Manual This manual uses the conventions and symbols shown in Table ii Table ii Typographical Conventions Type of Information Example of Typography Filenames and pathnames This structure is declared in usr include sys time h IRIX command names and options used in Update these variables with systune then build a normal text new kernel with autoconfig vf Names of program variables structures Global variable mainSema points to an IRIX and data types used in normal text semaphore which has type usema_t Names of IRIX system functions library Use mmap to map an object into the address functions and functions in example code space and munmap to remove it XXXV About This Manual Reader Comments xxxvi When complete lines of example code or commands are set off from normal text they are displayed as follows ipcrm s semid Parts of the code or command that need to be typed exactly as shown are displayed in a monospaced font Operands that you supply are italic
143. TIME Nov ABMON_12 LC_TIME Dec RADIXCHAR LC_NUMERIC Vd THOUSEP LC_NUMERIC et 369 Chapter 16 Internationalizing Your Application 370 Table 16 9 Cultural Data Names Categories and Settings continued Item Category Setting for the C Locale YESSTR LC_ALL yes NOSTR LC_ALL no CRNCYSTR LC_MONENTARY NLS Interfaces The NLS interfaces listed here are utilities and library functions NLS Utilities The list below identifies the minimum set of utilities that provide 8 bit transparency on all X Open compliant systems The definitions of these commands in terms of their syntax and parameters are not changed by the operation of NLS ar awk cancel cat cc cd chgrp chmod chown cmp cp cpio date diff echo ed egrep expr false grep find gencat Step iconv kill lex In Ip Ipstat Is mail mailx mkdir mv pack peat PS pr ps pwd red rm rmdir sed sh sleep sort stty tail tar tee test tr true tty umask uname uniq unpack uucp uulog uuname uupick uustat uuto uux wait we who Locale Specific Behavior The cc yacc and lex commands provide 8 bit transparency for characters contained in character strings character constants and comment strings An 8 bit character string enables a programmer to define default messages in languages other than English The support of 8 bit characters in identifier names is implementation defined The 8 b
144. Table 13 4 and described in the following sections e Getting the Thread ID on page 281 e Initializing Static Data on page 281 e Setting Event Handlers on page 281 e Terminating a Thread on page 282 e Joining and Detaching on page 283 Table 13 4 Functions for Managing Thread Execution Function pthread_atfork 3P pthread_cancel 3P pthread_cleanup_push 3P pthread_cleanup_pop 3P pthread_detach 3P pthread_exit 3P pthread_join 3P pthread_once 3P pthread_self 3P pthread_equal 3P pthread_setcancelstate 3P pthread_setcanceltype 3P pthread_testcancel 3P Purpose Register functions to handle the event of a fork Request cancellation of a specified thread Register function to handle the event of thread termination Unregister and optionally call termination handler Detach a terminated thread Explicitly terminate the calling thread Wait for a thread to terminate and receive its return value Execute initialization function once only Return the calling thread s ID Compare two thread IDs for equality Permit or block cancellation of the calling thread Specify deferred or asynchronous cancellation Permit cancellation to take place if it is pending Executing and Terminating Pthreads Getting the Thread ID Call pthread_self to get the thread ID of the calling thread A thread can use this thread ID when changing its own scheduling priority for example se
145. The clock_getres function returns the resolution of either of these clocks The program in Example 5 1 demonstrates the use of clock_gettime and clock_getres The following is an example of the output of this program ptime as executed on an Indy workstation ptime CLOCK_REALTIME value sec 835660711 ns 465330000 8 3566le 08 sec CLOCK_REALTIME units sec 0 ns 10000000 0 01 sec CLOCK_SGI_CYCLE value sec 83 ns 449744360 83 4497 sec CLOCK_SGI_CYCLE units sec 0 ns 40 4e 08 sec CLOCK_SGI_FAST units sec 0 ns 1000000 0 001 sec Example 5 1 Example of POSIX Time Functions i Program to exercise POSIX clock_gettime and clock_getres functions ptime r c R C F r display CLOCK_REALTIME value R display CLOCK_REALTIME resolution c display CLOCK_SGI_CYCLE value C display CLOCK_SGI_CYCLE resolution F display CLOCK_SGI_FAST resolution cannot get time from this Default is display everything rRcC include lt time h gt include lt unistd h gt for getopt include lt errno h gt errno and perror include lt stdio h gt void showtime const timespec_t tm const char caption printf s sec ld ns ld g sec n caption tm tv_sec tm tv_nsec double tm tv_sec double tm tv_nsec 1e9 131 Chapter 5 Signalling Events 132 main int argc char argv
146. This must be done on both the NFS file server and on all NFS clients where locks are requested Performance Impact Normally the NFS software uses a data cache to speed access to files Data read or written to NFS mounted files is held in a memory cache for some time and access requests to cached data is satisfied from memory instead of being read from the server Data caching has a major effect on the speed of NFS file access 193 Chapter 7 File and Record Locking 194 As soon as any process places a file or record lock on an NFS mounted file the file is marked as uncachable All I O requests for that file bypass the local memory cache and are sent to the NFS server This ensures consistent results and data integrity However it means that every read or write to the file at any offset and from any process incurs a network delay The file remains uncachable even when the lock is released The file cannot use the cache again until it has been closed by all processes that have it open Chapter 8 Using Asynchronous I O When you use asynchronous I O the work of buffering data and reading or writing a device is carried out in a parallel process or thread while the process or thread that requested the I O can continue doing other work In a multiprocessor system I O can be fully overlapped with processing About Synchronous and Asynchronous I O Conventional I O in UNIX is synchronous that is the process or threa
147. Topics in IRIX Programming Document Number 007 2478 010 CONTRIBUTORS Written by David Cortesi based on previous versions by Arthur Evans Wendy Ferguson and Jed Hartman updated by Susan Thomas Julie Boney and Steven Levine Production by Karen Jacobson Engineering contributions by Ivan Bach Greg Boyd Joe CaraDonna Srinivas Lingutla Bill Mannell Paul Mielke Huy Nguyen James Pitcairne Hill Paul Roy Jonathan Thompson and Ira Pramanick 1996 2004 Silicon Graphics Inc All rights reserved provided portions may be copyright in third parties as indicated elsewhere herein No permission is granted to copy distribute or create derivative works from the contents of this electronic documentation in any manner in whole or in part without the prior written permission of Silicon Graphics Inc LIMITED RIGHTS LEGEND The electronic software version of this document was developed at private expense if acquired under an agreement with the USA government or any contractor thereto it is acquired as commercial computer software subject to the provisions of its applicable license agreement as specified in a 48 CFR 12 212 of the FAR or if acquired for Department of Defense units b 48 CFR 227 7202 of the DoD FAR Supplement or sections succeeding thereto Contractor manufacturer is Silicon Graphics Inc 1500 Crittenden Lane Mountain View CA 94043 1351 Silicon Graphics CHALLENGE Indy IRIS IRIX Onyx and OpenGL
148. _SYNC each call to write blocks until the data has been written to disk This gives you a way of ensuring that all output is complete as it is created If you combine O_SYNC access with asynchronous I O you can let the asynchronous process suffer the delay see About Asynchronous I O on page 196 Synchronous output is still buffered output data is copied to a kernel buffer before writing The meaning of O_SYNC is that the file data is all present even if the system crashes For this reason each write to an O_SYNC file can cause a write of file metadata as well as the file data itself Specifying O_ DSYNC causes a write of file data without waiting for the file metadata These extra writes can make synchronous output quite slow The O_SYNC option takes effect even when the amount of data you write is less than the physical blocksize of the disk or when the output does not align with the physical boundaries of disk blocks In order to guarantee writing of misaligned data the kernel has to read disk blocks update them and write them back If you write using incomplete disk blocks 512 bytes on block boundaries synchronous output is slower Using Direct I O Using Direct I O You can bypass the kernel s buffer cache completely by using the option O_DIRECT Under this option writes to the file take place directly from your program s buffer to the device the data is not copied to a buffer in the kernel first In order to us
149. _send function blocks if the queue is full unless the O_NONBLOCK attribute is in effect for the queue Receiving a Message To receive a message call mq_receive specifying the queue the address and size of a buffer and the address of an integer to receive the message s priority The size of the buffer must be at least as large as the maximum size allowed by that queue You can learn this size using mq_getattr see Example 6 4 for an example of this The mq_receive function blocks if the queue is empty unless O_NONBLOCK is in effect for the queue The message returned is always the oldest message in the highest priority class Using Asynchronous Notification Some applications are designed so that each process or thread does nothing but process messages Ina design of this kind it makes sense for a process or thread to suspend itself when no messages are available on its queue 143 Chapter 6 Message Queues 144 Other applications are designed so that one process or thread performs multiple tasks besides handling messages or handles messages from multiple queues In this kind of program a process cannot suspend itself on a single message queue Instead it needs to do other work and only request a message when a message is available One way to do this is to set the O NONBLOCK flag and to periodically poll for a message by calling mq_receive and testing its return code However this is inefficient The POSIX m
150. a Regular to correspond to the line Utopia Regular adobe utopia medium r normal 0 0 0 0 p 0 is08859 1 in usr lib X11 fonts ps2xlfd_map The file was put in the directory usr lib DPS AFM Font metric files for a large outline font in the CID keyed format should be put in the directory usr lib X11 fonts CID character collection AFM There is one AFM file for each CIDFont file and one AFM file for each CID keyed font Downloading a Type 1 Font to a PostScript Printer Some outline fonts are usually built into a PostScript printer You can find out which fonts are known to the PostScript interpreter in your printer by sending the following file to that printer oe Produce a list of available fonts 100 string def Times Roman findfont 12 scalefont setfont y 700 def 72 y moveto FontDirectory pop f cvs show 72 y y 13 sub def y moveto forall showpage Utopia fonts are not usually built into PS printers If you try to print a document that requires a Utopia font on a PS printer that does not have that font a warning message about the replacement of a missing font with a Courier font is sent to the file usr spool lp log on the system to which that PS printer is attached 329 Chapter 15 Working With Fonts You can download a Type 1 font to a PS printer in either of the following two ways e You can insert a Type 1 font file at the beginning of the PostScript file that needs that font You should have a
151. a complete discussion of the Ada 95 task facility refer to the Ada 95 Reference Manual which installs with the Ada 95 compiler GNAT product Parallel Execution Models Statement Level Parallelism The finest level of granularity is to run individual statements in parallel This is provided using any of three language products e MIPSpro Fortran 77 supports compiler directives that command parallel execution of the bodies of DO loops The MIPSpro POWER Fortran 77 product is a preprocessor that automates the insertion of these directives in a serial program e MIPSpro Fortran 90 supports parallelizing directives similar to MIPSpro Fortran 77 and the MIPSpro POWER Fortran 90 product automates their placement e MIPSpro POWER C supports compiler pragmas that command parallel execution of segments of code The IRIS POWER C analyzer automates the insertion of these pragmas in a serial program In all three languages the run time library which provides the execution environment for the compiled program contains support for parallel execution The compiler generates library calls The library functions create lightweight processes using sproc and distribute loop iterations among them The run time support can adapt itself dynamically to the number of available CPUs Alternatively you can control it either using program source statements or using environment variables at execution time to use a certain number of CPUs Stateme
152. ability to get information about a semaphore set or to modify its attributes These operations are summarized in Table 4 12 Table 4 12 SVR4 Semaphore Set Management Operations Keyword Operation Can Be Used By IPC_STAT Get information about the set Any process having read access IPC_SET Set owner UID owner GID or access Creator UID owner UID or permissions superuser IPC_RMID Remove the set from the IPC name Creator UID owner UID or space superuser GETALL Copy current values of allsemaphores Any process having read access to an array SETALL Set current values of all semaphores Any process having write access from an array of integers Examples of some of these uses can be found under Example Uses of semctl for Management on page 104 IRIX Facilities for Mutual Exclusion In addition semctl allows you to query or set information about individual semaphores within the set as summarized in Table 4 13 Table 4 13 SVR4 Semaphore Management Operations Keyword Operation Can Be Used By GETVAL Return value of one semaphore Any process having read access GETPID Return process ID of the process that Any process having read access last operated on a semaphore GETNCNT Return number of processes waiting Any process having read access for one semaphore to exceed zero GETZCNT Return number of processes waiting Any process having read access for one semaphore to equal zero SETVAL Set current
153. access permissions determine which user IDs and group IDs can share the file The functions you use to manage a shared arena are discussed in the following topics and are summarized in Table 3 2 Table 3 2 IRIX Shared Arena Management Functions Function Name Purpose and Operation usconfig 3 Establish the default size of an arena the number of concurrent processes that can use it and the features of IPC objects in it usinit 3 Create an arena or join an existing arena usadd 3 Join an existing arena Initializing Arena Attributes A program creates a shared memory arena with the usinit function However many attributes of a new arena are set by preceding calls to usconfig The normal sequence of operations is to make several calls to usconfig to establish arena attributes then to make one call to usinit to create the arena 61 Chapter 3 Sharing Memory Between Processes 62 You call usconfig to establish the features summarized in Table 3 3 Table 3 3 Arena Features Set Using usconfig usconfig Flag Name Meaning CONF_INITSIZE The initial size of the arena segment The default is 64 KB Often you know that more is needed CONF_AUTOGROW Whether or not the arena can grow automatically as more IPC objects or data objects are allocated default yes CONF_INITUSERS The largest number of concurrent processes that can use the arena The default is 8 if more processes than this will use IPC the l
154. ads IEEE 1003 1c Other IPC features are compatible with the two major schools of UNIX programming BSD UNIX and AT amp T System V Release 4 SVR4 UNIX Table 2 1 summarizes the types of IPC that IRIX supports and lists the systems with which IRIX is compatible Table 2 1 Types of IPC and Compatibility Type of IPC Purpose Compatibility Signals A means of receiving notice of a software or POSIX SVR4 BSD hardware event asynchronously Shared memory A way to create a segment of memory that is mapped POSIX IRIX SVR4 into the address space of two or more processes each of which can access and alter the memory contents Semaphores Software objects used to coordinate access to POSIX IRIX SVR4 countable resources Locks Mutexes Software objects used to ensure exclusive use of POSIX IRIX and Condition single resources or code sequences Variables Barriers Software objects used to ensure that all processesina IRIX group are ready before any of them proceed Message Queues Software objects used to exchange an ordered POSIX SVR4 sequence of messages File Locks A means of gaining exclusive use of all or part of a SVR4 BSD file Sockets Virtual data connections between processes that may BSD be in different systems 46 Types of Interprocess Communication Available The different implementations of these IPC features can be summarized as follows POSIX compliant library calls are provided for signal handling
155. age 113 describes signal facilities in general and details the differences between the POSIX SVR4 and BSD interfaces e Timer Facilities on page 127 describes POSIX and IRIX methods of defining timestamps and intervals A signal is a notification of an event sent asynchronously to a process Some signals originate from the kernel in response to hardware traps for example the SIGFPE signal that notifies of an arithmetic overflow or the SIGALRM that notifies of the expiration of a timer interval Other signals are issued by software For a detailed formal discussion of signals read the signal 5 reference page A process can block all signals or selected signals ignore some signals or request a default system handling for some signals When a signal that has been sent to a process is blocked by the process the signal remains pending When a signal is not blocked the process receives the signal In a multithreaded process signals can be blocked or received by individual threads When receiving a signal a process or thread can handle the signal by an asynchronous call into a signal handling function Alternatively using the POSIX interface a process or thread can handle signals synchronously as a stream of event objects 113 Chapter 5 Signalling Events 114 Signal Numbers IRIX supports the following 64 signal numbers Same meanings as SVR4 and BSD see Table 5 1 Reserved by IRIX kernel 1 31 32 33 48 49 6
156. age has been modified the kernel calls the write entry point of the device driver to write the page It also writes any modified pages when the file mapping is changed by munmap or another mmap call when the program applies msync to the segment or when the program ends When mapping a file for input only when the prot argument of mmap does not contain PROT_WRITE you can use either MAP_SHARED or MAP_PRIVATE When writing is allowed you must use MAP_SHARED or changes will not be reflected in the file 15 Chapter 1 Process Address Space 16 Tip Memory mapping provides an excellent way to read a file containing precalculated constant data used by an interactive program Time consuming calculation of the data elements can be done offline by another program the other program also maps the file in order to fill it with data You can lock a mapped file into memory This is discussed further under Locking and Unlocking Pages in Memory on page 23 Mapped File Sizes Because the potential 32 bit address space is more than 2000 megabytes and the 64 bit address space vastly greater you can in theory map very large files into memory However many segments of the virtual address space are preassigned to DSOs see Address Space Boundaries on page 4 and the file usr lib so_locations and this restricts the available size of maps in 32 bit space To map an entire file follow these steps 1 Open the file to get a
157. aicos TC Islands Tuvalu TV Uganda UG Ukraine UA United Arab AE United Kingdom GB United States Minor UM Emirates Outlying Islands Uruguay UY Vanuatu VU Vatican City State VA Venezuela VE Viet Nam VN Virgin Islands VG British Virgin Islands VI Wallis and WF Western Sahara EH USA Futuna Islands Yemen YEor Yugoslavia YU Zaire ZR YD Former Zambia ZM Zimbabwe ZW Index Symbols Numbers 32 bit addressing address size 3 page size 5 64 bit addressing address size 3 page size 5 shared memory 54 8 bit clean codesets 347 A address range 3 address space 3 10 cannot undefine 6 copy on write pages 10 defining addresses 5 heap segment 4 interrogating 11 limits of 6 low 4 MB reserved 23 lowest used address 4 protection 28 read only pages 10 resident set size 10 segment 4 segment reserved for user mapping 23 stack segment 4 text segment 4 virtual size of 6 16 aio_cancel 201 aio_error 202 aio_fsync 201 aio_read 200 implies aio_init 198 aio_sgi_init 199 aio_suspend 202 aio_write 200 implies aio_init 198 arenas IRIX IPC 49 Argentina country code 415 ASCII strings See internationalization codesets ASCII asynchronous I O 195 228 aiocb structure 198 202 aioinit_tstructure 199 cancelling 201 file sync 201 initializing 198 list I O 201 multiple operations to one file 208 notification methods 202 POSIX 1003 1b 1993 197 request priori
158. al xxxiv Other Useful References xxxiv Obtaining Manuals xxxv Conventions Used in This Manual xxxv Reader Comments xxxvi Process Address Space 3 Defining the Address Space 3 Address Space Boundaries 4 Page Numbers and Offsets 5 Address Definition 5 Address Space Limits 6 Delayed and Immediate Space Definition 7 Page Validation 9 Read Only Pages 10 Copy on Write Pages 10 Interrogating the Memory System 11 Contents Mapping Segments of Memory 12 Segment Mapping Function mmap 12 Describing the Mapped Object 13 Describing the New Segment 13 Mapping a File forI O 15 Mapped File Sizes 16 Apparent Process Size 16 Mapping Portions of a File 17 File Permissions 17 NFS Considerations 17 File Integrity 18 Mapping a File for Shared Memory 19 Mapping a Segment of Zeros 19 Mapping Physical Memory 20 Mapping Kernel Virtual Memory 20 Mapping a VME Device 20 Choosing a Segment Address 21 Segments at Fixed Offsets 21 Segments at a Fixed Address 22 Contents Locking and Unlocking Pages in Memory 23 Memory Locking Functions 24 Locking Program Text and Data 24 Locking Mapped Segments 25 Locking Mapped Files 26 Unlocking Memory 27 Additional Memory Features 27 Changing Memory Protection 28 Synchronizing the Backing Store 28 Releasing Unneeded Pages 29 Using Origin2000 Nonuniform Memory 29 About Origin Hardware 30 Basic Building Blocks 30 Uniform Addressing 30 Cache Coherency 31 Cache Coherency in CHALLENGE Systems 32 Cache Cohere
159. all from another node e There is a time penalty for some interprocess communication When data passes between programs in different nodes it passes over the HIPPI network which takes longer than a memory to memory transfer e Peripherals are accessible only in the node to which they are physically attached Parallel Execution Models Nevertheless it is possible to design an application that executes concurrently in multiple nodes of an Array The message passing interface MPI is designed specifically for this Hierarchic Nonuniform Memory Systems The Origin2000 system uses a memory hierarchy A certain amount of memory is a physical part of each node The hardware creates the image of a single system memory The memory installed in any node can be accessed from any other node as if all memory were local However the node number is part of the physical address of a word of memory There is a multiple level hierarchy of speed memory in the same node as the CPU is accessed in the least amount of time while memory in any other node takes an additional fraction of a microsecond to access The time penalty depends on the relative location of the two nodes in the system These are the results of this design e There is a single address map A word of memory can be addressed from any node e There is a time penalty for some accesses depending on the node that requests the memory and the node that contains it However this time cost
160. ame of the queue must be given following all options c count Number of messages to send The default is 1 q Tells program not to display a line for each message received n Use the O_NONBLOCK flag with mq_open You can use the q option to keep the program from displaying messages Do this when receiving a large number of messages for example to test performance POSIX Message Queues Example 6 4 Program to Demonstrate mq_receive Program to test mq_receive 3 mq_receive c lt count gt n q lt path gt c lt count gt number of messages to request default 1 n use O_NONBLOCK flag on open q quiet do not display messages lt path gt path to message queue required The program calls mq_ receive lt count gt times or until an error occurs bat include lt mqueue h gt message queue stuff include lt unistd h gt for getopt include lt errno h gt errno and perror include lt fcntl h gt O_RDONLY include lt stdlib h gt calloc 3 include lt stdio h gt int main int argc char argv char path gt first non option argument int oflags O_RDONLY open flags O_NONBLOCK may be added int quiet 0 q option int count 1 number of messages to request mqd_t mad queue descriptor from mq_open char msgptr gt allocated message space unsigned int msg_prio received message priority int c
161. ample using the lockf function Since it does not support read locks all write locks are referenced generically as locks Example 7 6 Record Locking Using lockf This function is called with a file descriptor and the offsets to three records in it this here and next The caller is assumed to hold no locks on any of the records This function tries to lock here and next using lockf If locks on here and next are obtained Set a lock on this Return index to this record If any lock is not obtained Remove all other locks Return 1 ef long set3Locks int fd long this long here long next Set a lock on here void lseek fd here 0 if lockf fd F_LOCK sizeof struct record lt 0 return 1 Lock this void lseek fd this 0 if lockf fd F_LOCK sizeof struct record lt 0 Failed to lock this clear here lock void lseek fd here 0 void lockf fd F_ULOCK sizeof struct record return 1 Lock next void lseek fd next 0 if lockf fd F_LOCK sizeof struct record lt 0 Failed to lock next release here void lseek fd here 0 void lockf fd F_ULOCK sizeof struct record and remove lock on this void lseek fd this 0 Using Record Locking void lockf fd F_ULOCK sizeof struct record return 1 return this Locks are removed in t
162. an Input Method XOpenIM opens an input method appropriate for the locale and modifiers in effect when it is called see the XOpenIM 3X11 reference page The locale is bound to that IM and cannot be changed But you could open another IM if you wanted to switch later Strings returned by XmbLookupString and XwcLookupString are encoded in the locale that was current when the IM was opened regardless of current input context 395 Chapter 16 Internationalizing Your Application 396 The syntax is XIM XOpenIM Display dpy XrmDataBase db char res_name char res_class The res_name is the resource name of the application res_class is the resource class and db is the resource database that the input method should use for looking up resources private to itself Any of these can be NULL The fragment in Example 16 7 shows how easy it is to open an input method Example 16 7 Opening an IM XIM im im XOpenIM dpy NULL NULL NULL if im NULL exit_with_error XOpenIM finds the IM appropriate for the current locale If XSupportsLocale has returned good status see Initialization for Xlib Programming and XOpenIM fails something is amiss with the administration of the system XSetLocaleModifiers determines configure locale modifiers The local host X locale modifiers announcer the XMODIFIERS environment variable is appended to the modifier list to provide default values on the locale host Th
163. and strings are convertible to wchars using mbtowc for individual characters and mbstowcs for strings see the mbtowc 3 and mbstowcs reference pages Finding the Number of Bytes in a Character To find out how many bytes make up a given single MB character use mblen as shown in Example 16 1 see also the mblen 3 reference page Character Sets Codesets and Encodings Example 16 1 Find Number of Bytes in an MB Character include lt stdlib h gt size_t n int len char pStr len mblen pStr n examine no more than n bytes It is the application s responsibility to ensure that pStr points to the beginning of a character not to the middle of a character The maximum number of bytes in a multibyte character is MB_LEN_MAX which is defined in limits h The maximum number of bytes in a character under the current locale is given by the macro MB_CUR_MAX defined in stdlib h How Many Bytes in an MB String Since strlen simply counts bytes before the first NULL it tells you how many bytes are in an MB string How Many Characters in an MB String When mbstowcs converts MB strings to WC strings it returns the number of characters converted This is the simplest way to count characters in an MB string Note Many code segments that deal with individual characters within a string are better served by wide character strings Because counting often involves conversion such segments are often better serv
164. and writing cache for its neighbor proc ay typedef struct child read only to child char fname 100 int fd void buffer int procid ort t fsize rvead write to child usema_t sema off_t outbase off_t inbase clock_t etime aiocb_t acb y ehidta t KR KK KK KR RR RR RR RR RRR RA AA A A A A A A A A A I He 212 Asynchronous I O Example Globals accessible to all processes char ofName NULL output file name string int outFD output file descriptor usptr_t arena arena where everything is built barrier_t convene barrier used to sync up int nprocs 1 1 number of child procs child_t array array of child_t structs in arena int errors 0 always incremented on an error BRK KK KR RR RR RR RRR RR RRR AAR A A A A A A A A A A A A A A I A forward declaration of the child process functions x void inProcO void arg size_t stk polls with aio_error void inProcl void arg size_t stk uses aio_suspend void inProc2 void arg size_t stk uses a signal and semaphore void inProc3 void arg size_t stk uses a callback and semaphore BRK RK KK KK RR RR RR RR A RR RRR RRA A A A A A A A A A A A A I A He The main int main int argc char argv char tmpdir gt name string of temp dir int nfiles how many input files on cmd line int argno loop counter chi
165. andler executes and unblocked when your handler returns When set the same signal could be taken while your handler executes resulting in multiple entries to the handler When not set if this signal interrupts a blocked system function the system function returns EINTR When set the system function is restarted System V Signal Facility The System V signal interface is compatible with code ported from UNIX System V It includes compatibility for release 3 SVR3 and release 4 SVR4 Table 5 4 summarizes the functions you use to manage signals through this interface Signals Table 5 4 Functions for SVR4 Signal Handling Function Purpose kill 2 Send a signal to a process or process group A duplicate of a pending signal is discarded sigsend 2 Send a signal to a set of processes or process groups specified in a variety of ways for example by user ID signal 2 SVR3 call to establish handling policy of default ignore or catch for a specified signal sigset 2 SVR amp 4 call to establish handling policy of default ignore or catch for a specified signal sighold 2 Hold block a specified signal sigignore 2 Set the handling for a specified signal to Ignore sigrelse 2 Release unblock a specified signal sigpause 2 Suspend the calling process until a specified signal arrives Only asynchronous signal handling is supported by the System V interface Also you must block and unblock signals individua
166. any processes as necessary Each process begins to execute the same block of statements The processes share global variables while each allocates its own copy of variables that are local to one iteration of a loop such as a loop index When a process completes its portion of the work of that parallel section it returns to the run time library code where it picks up another portion of work if any work remains or suspends until the next time it is needed At the end of the parallel section all extra processes are suspended and the original process continues to execute the serial code following the parallel section Controlling the Degree of Parallelism You can specify the number of lightweight processes that are started by a program In IRIS POWER C you can use pragma numthreads to specify the exact number of processes to start but it is not a good idea to embed this number in a source program In all implementations the run time library by default starts enough processes so there is one for each CPU in the system That default is often too high since typically not all CPUs are available for one program Managing Statement Parallel Execution The run time library checks an environment variable MP_SET_NUM_THREADS for the number of processes to start You can use this environment variable to choose the number of processes used by a particular run of the program thereby tuning the program s requirements to the system load You can e
167. application programs for example to generate PostScript code for a specified document Follow these steps to add a font metric file for an outline font in the Type 1 format 1 Log in as root 2 Put Adobe Font Metric files in the directory usr lib DPS AFM 3 In order for the new fonts to be recognized by Ghostscript and thus be available to the gsview tool you must add the new fonts to the end of the Fontmap GS file Since later entries in Fontmap GS override earlier entries a font you add at the end supersedes any corresponding fonts supplied with Ghostscript and defined earlier in the file The format for entries in Fontmap GS is documented in the Fontmap GS file itself When you install Ghostscript on your system this file is available in the following location usr share ghostscript ghostscript_revision 1lib Fontmap Gs ghostscript_revision is the version of Ghostscript installed on the system In order for the new fonts to be available to the xpdf tool you must add the fonts to the usr etc xpdfrc file For information on this file see the xpdfrc 5 man page The name of an AFM file must match the PostScript font name as given in the file usr lib X11 fonts ps2xlfd_map see Locations of Font and Font Metric Files on page 319 Downloading a Type 1 Font to a PostScript Printer For example Adobe provided the Utopia Regular font metric file UTRG____ AFM When this font was added to IRIX the name was changed to Utopi
168. are it among the address spaces of multiple processes All produce the same result a segment of memory that can be accessed or updated asynchronously by more than one process You have to design protocols that prevent one process from changing shared data while another process is using the same data see Chapter 4 Mutual Exclusion This chapter covers three major topics e POSIX Shared Memory Operations on page 55 describes the POSIX functions for sharing memory e TRIX Shared Memory Arenas on page 61 describes IRIX shared memory arenas e System V Shared Memory Functions on page 71 describes the SVR4 functions Overview of Memory Sharing The address space is the range of memory locations that a process can use without an error The concept of the address space is covered in detail in Chapter 1 Process Address Space In a pthreads program all threads use the same address space and share its contents In a program that starts multiple lightweight processes with sproc all processes share the same address space and its contents In these programs the entire address space is shared automatically Normally distinct processes created by the fork or exec system calls have distinct address spaces with no writable contents in common The facilities described in this chapter allow you to define a segment of memory that can be part of the address space of more than one process Then processes or threads
169. are registered trademarks and SGI the SGI logo Developer Magic Impressario Indigo IRIS Inventor IRIS GL IRIS IM IRIS Insight IRIS POWER C IRIS Showcase IRIS Performer O2 OCTANE Onyx2 Origin200 Origin2000 POWER CHALLENGE POWER CHALLENGEarray POWER Series REACT and XFS are trademarks of Silicon Graphics Inc in the United States and or other countries worldwide Cray is a registered trademark and CRAY T3E and CrayLink are trademarks of Cray Inc MIPS R4000 and R8000 are registered trademarks and MIPSpro and R10000 are trademarks of MIPS Technologies Inc Ada is a registered trademark of Ada Joint Program Office U S Government AT amp T is a trademark of AT amp T Inc NFS is a registered trademark of Sun Microsystems Inc OSF Motif is a trademark of Open Software Foundation Inc POSIX is a registered trademark of the Institute of Electrical and Electronic Engineers Inc IEEE PostScript and Display Postscript are registered trademarks of Adobe Systems Inc Speedo is a trademark of Bitstream Inc UNIX is a registered trademark in the United States and other countries licensed exclusively through X Open Company Ltd X Window System is a trademark of X Consortium Inc Topics in IRIX Programming Document Number 007 2478 010 Contents List of Examples xxv List of Figures xxvii List of Tables xxix About This Manual xxxiii What This Manual Contains xxxiii What You Should Know Before Reading This Manu
170. are writing a truly extraordinary application then this section is for you This section on translating user input covers these topics e About User Input and Input Methods on page 391 presents an overview of user input and input methods e About X Keyboard Support on page 392 covers X keyboard support including keys keycodes keysyms and composed characters e Input Methods IMs on page 395 describes how input methods are opened and closed e IM Styles on page 397 discusses the use and naming of IM styles e Input Contexts ICs on page 400 explains an IM styles IC values pre edit and status attributes and creating and using ICs e Events Under IM Control on page 404 describes differences in processing events under IM control including XFilterEvent and LookupString routines About User Input and Input Methods Just as internationalized programs cannot assume that data is in ASCII they cannot assume that user input will use any specific keyboard Keyboards change from country to country and language to language internationalized software should never assume that a certain position on the keyboard is bound to a certain character or that a given character will be available as a single keystroke on all keyboards No useful physical keyboard not even one specifically designed for multilingual work could possibly contain a key for every character we would ever wish to type Certainly ther
171. ared objects You acquire a mutex by calling pthread_mutex_lock and release it with pthread_mutex_unlock When a thread must not be blocked it can use pthread_mutex_trylock to test the mutex and lock it only if it is available Condition Variables A condition variable provides a way in which a thread can wait for an event or condition defined by the program to be satisfied Condition variables use mutexes to synchronize the wait and wakeup operations Synchronizing Pthreads Preparing Condition Variables Like mutexes and threads themselves condition variables are supplied with a mechanism of attribute objects pthread_condattr_t objects and static and dynamic initializers Only the condition variable for the process shared attribute can be initialized in this implementation The functions for initializing one are summarized in Table 13 9 Table 13 9 Functions for Preparing Condition Variables Function Purpose pthread_condattr_init 3P Initialize a pthread_condattr_t to default attributes pthread_condattr_destroy 3P Uninitialize a pthread_condattr_t pthread_condattr_getpshared 3P Get the process shared attribute pthread_condattr_setpshared 3P Set the process shared attribute pthread_cond_init 3P Initialize a condition variable based on an attribute object pthread_cond_destroy 3P Uninitialize a condition variable A condition variable must be initialized before use You can do this in one of three wa
172. arget file is physically mounted On the server that rpc lockd issues the lock request locally The server rpc lockd sends the result success or failure back to the client rpc lockd The result is passed back to the calling process When the lock succeeds on the server side rpc lockd on the client system requests another daemon rpc statd to monitor the NFS server that implements the lock If the server fails and then recovers rpc statd will be informed It then tries to reestablish all active locks If the NFS server fails and recovers and rpc lockd is unable to reestablish a lock it sends a signal SIGUSR1 to the process that requested the lock When a process writes to a write locked record the data is sent directly to the NFS server bypassing the local NFS buffer cache This can have a significant impact on file performance Configuring NFS Locking When rpc lockd is not running in the NFS client system or in the NFS server system a cross system lock cannot be established In this case locks are effective within the local system but are not effective against contending file access from other systems To discover whether rpc lockd is running use the chkconfig command o etc chkconfig grep lockd If the returned value is off rpc lockd is not running and locks have local scope only To use rpc lockd the administrator must configure it on as follows o etc chkconfig lockd on Then the system must be rebooted
173. ariables 273 Chapter 13 Thread Level Parallelism Overview of POSIX Threads 274 A thread is an independent execution state that is a set of machine registers a call stack and the ability to execute code When IRIX creates a process it also creates one thread to execute that process However you can write a program that creates many more threads to execute in the same address space For a comparison of pthreads to processes see Thread Level Parallelism on page 249 POSIX threads are similar in some ways to IRIX lightweight processes made with sproc You use pthreads in preference to lightweight processes for two main reasons portability and performance A program based on pthreads is normally easier to port from another vendor s equipment than a program that depends on a unique facility such as sproc Table 13 1 summarizes some of the differences between pthreads and lightweight processes Table 13 1 Comparison of Pthreads and Processes Attribute POSIX Threads Lightweight Processes UNIX Processes Source portability Standard interface sproc is unique to fork is a UNIX portable between IRIX standard vendors Creation overhead Relatively small Moderately large Quite large Block Unblock Few microseconds Many microseconds Many microseconds Dispatch Overhead Address space Shared Shared or copy on Separate write or separate Memory mapped Shared Shared or copy on Explicit sharing only files and arena
174. as passed e The arena was not configured to allow enough using processes and no more users can be allowed A child process can join an arena automatically simply by using a semaphore lock or barrier that was allocated within that arena These function calls perform an automatic call to usadd However they can also encounter the error that too many processes are already using the arena It is best for the child process to check for this condition with an explicit call to usadd IRIX Shared Memory Arenas Allocating in an Arena Allocating shared memory from a shared arena is much like the regular process of allocating memory using the malloc and free library routines The functions related to allocation within an arena are summarized in Table 3 4 Table 3 4 IRIX Shared Memory Arena Allocation Functions Function Name Purpose and Operation usmalloc 3 Allocate an object of specified size in an arena uscalloc 3 Allocate an array of zero filled units in an arena usmemalign 3 Allocate an object of specified size on a specified alignment boundary in an arena usrealloc 3 Change the allocated size of an object in an arena usrealloc 3 Change the allocated size of an array created with uscalloc usmallocblksize 3 Query the actual size of an object as allocated usfree 3 Release an object allocated in an arena usmallopt 3 Tune the allocation algorithm using constants described in amallopt 3 usmallinfo 3 Q
175. ate return with an error code EAGAIN when it sends a message to a full queue or requests a message from an empty queue When the program omits O_NONBLOCK it specifies that it is willing to be suspended in these situations The O_NONBLOCK flag applies to all operations using the queue descriptor returned by mq_open The same queue opened under a different descriptor can have different blocking behavior The blocking behavior can be changed by applying mq_setattr to the queue descriptor If the program normally wants to allow suspension but in a particular situation wants to avoid suspension it can apply mq_setattr to change the blocking state and then set it back again POSIX Message Queues Using Message Queues The POSIX functions for using an open queue are summarized in Table 6 3 Table 6 3 POSIX Functions for Using Message Queues Function Name Purpose and Operation mq_send 3 Send a message to a queue mq_receive 3 Receive a message from a queue mq_notify 3 Request asynchronous notification of a message on a queue Sending a Message To send a message to a queue call mq_send specifying the queue the address and length of the message data and an integer specifying the priority class of the message Messages on the queue are retained in arrival sequence within priority classes The message is copied out of the caller s buffer so the buffer can be reused immediately after a successful send The mq
176. ation T where Trepresents any of the printf conversion characters is implicitly matched to an argument value by position In order to deal with variably ordered strings printf allows an argument position index D to appear in the conversion specification following the so that where a format string contains T it can now contain D T The value D set off by a currency symbol selects the argument from the argument list to be used This means you can write printf 2nd parameter is 2Ss the lst is 1 s pl p2 381 Chapter 16 Internationalizing Your Application 382 The second parameter is printed first with the first parameter printed second For example char store Macy s char obj a cup printf At 1 s I bought 2Ss n store obj printf I bought 2 s at 1 s n store obj This code displays At Macy s I bought a cup I bought a cup at Macy s In English we are able to come up with strings suitable for either word order in some other language we might not be so lucky Nor can we predict which order such languages might prefer So the developer has no way of knowing how to create traditional printf format strings suitable for all languages Developers should therefore use message catalogs for their printf format strings that take linguistic parameters and allow localizers to localize the format strings as well as text strings This means that the localizer has much greater
177. attr bzero void amp attr sizeof attr attr fsx_xflags XFS_XFLAG_REALTIME attr fsx_extsize esize int rtfd open path O_CREAT O_EXCL O_DIRECT if 1 rtfd perror open new file return 1 if 1 fentl rtfd F_FSSETXATTR attr perror fcntl set rt amp extent return 1 return rtfd first write to it creates file Requesting a Guarantee To obtain a guaranteed rate a program places a reservation for a specified part of the I O capacity of a file or a filesystem In the request the program specifies e the file or filesystem to be used e the start time and duration of the reservation e the time unit of interest typically 1 second e the amount of data required in any one unit of time For example a reservation might specify starting now for 90 minutes 1 megabyte per second A process places a reservation by calling either grio_request_file or grio_request_fs refer to the grio_request_file 3X and grio_request_fs 3X reference pages The GRIO daemon ggd keeps information on the transfer capacity of all XFS volumes as well as the capacity of the controllers and busses to which they are attached When you request a reservation XFS tests whether it is possible to transfer data at that rate from that file during that time period This test considers the capacity of the hardware as well as any other reservations that apply during th
178. barrier explicit or general If you invoke __compare_and_swap passing only the pointer and two value arguments the compiler can move no code across that source line Alternatively you can list specific variables as additional arguments to ___compare_and_swap this is why the functions are shown as having a variable number of arguments When you do so the compiler cannot move assignments to the named variables across this point but can move assignments to other variables if the optimizer needs to System V Facilities for Mutual Exclusion The System V Release 4 SVR4 semaphore facility lets you create persistent semaphores that can be used to coordinate any processes or threads The SVR4 facility differs from POSIX named semaphores in two ways e Each object is a set of from 1 to 25 independent semaphores rather than a single semaphore A process can operate on any selection of semaphores in a set in one system call IRIX Facilities for Mutual Exclusion e You can use SVR4 semaphores in ways that IRIX and POSIX do not support incrementing or decrementing by more than 1 and waiting for a zero value e The name of a set is an integer in a kernel table rather than a pathname in the filesystem see SVR4 IPC Name Space on page 50 The functions used to create and operate on semaphore sets are summarized in Table 4 11 Table 4 11 SVR4 Semaphore Management Functions Function Name Purpose and Operation semget 2 C
179. before this function is called or it could b ntered afterward xJ uspsema pch gt sema Since this process executes only one aio operation at a time we can return the status of that operation In a more complicated design if a signal could arrive from more than one pending operation this function could not return status Kf return aio_error amp pch gt acb void inProc2 void arg size_t stk 224 child_t pch arg starting arg is gt child_t for my file aiocb_t pab amp pch gt ach base address of the aiocb_t in child_t int ret as long as this is 0 all is ok int bytes bytes read on each input Initialize request a signal in aio_sigevent The address of the child_t struct is passed as the siginfo value for use in the signal handler Ref pab gt aio_sigevent sigev_notify SIGEV_SIGNAL pab gt aio_sigevent sigev_signo AIO_SIGNUM pab gt aio_sigevent sigev_value sival_ptr void pch pab gt aio_buf pch gt buffer always the same Initialize set up a signal handler for AIO_SIGNUM Asynchronous I O Example struct sigaction sa ret sigaction AIO_SIGNUM amp sa NULL if ret terrors if DO_SPROCS Wait for the starting gun KY barrier convene nprocs else if ret return endif pch gt etime clock do read and write read and write
180. bytes where to write next time while ret amp amp bytes BLOCKSIZE The loop is complete If no errors so far use aio_fsync to ensure that output is complete This requires waiting yet again x if ret if ret aio_fsync O_SYNC pab ret inWait1 pch Flag any errors for the parent proc If none count elapsed time a if ret terrors lse pch gt etime clock pch gt etime if DO_SPROCS Rendezvous with the rest of the family then quit Xy barrier convene nprocs endif end inProc0 KK KK KR RR RR RR A RA RA RR AA AAR A A A A A A A A A A A A A I HA inProc2 requests a signal upon completion of an I O After starting an operation it P s a semaphore which is V d from the signal handler Xfi define AIO_SIGNUM SIGRTMIN 1 arbitrary choice of signal number void sigHandler2 const int signo const struct siginfo sif 223 Chapter 8 Using Asynchronous I O int In this minimal signal handler we pick up the address of the child_t info structure which was put in aio_sigevent sigev_valu field during initialization and use it to find the semaphore child_t pch sif gt si_value sival_ptr usvsema pch gt sema return stop here with dbx to print the above address inWait2 child_t pch Wait for any signal handler to post the semaphore The signal handler could have been entered
181. c getopt argc argv p b m cx switch c case p permissions perms int strtoul optarg NULL 0 break case b message size buf mq_msgsize int strtoul optarg NULL 0 break case m max messages buf mq_maxmsg int strtoul optarg NULL 0 break POSIX Message Queues case c use O_CREAT oflags O_CREAT break case x use O_EXCL oflags O_EXCL break default unknown or missing argument return 1 switch while if optind lt argc path argv optind first non option argument else printf Queue pathname required n return 1 mqd mq_open path oflags perms amp buf if 1 mqd if mq_getattr mqd amp buf printf flags 0x x maxmsg d msgsize d curmsgs d n buf mq_flags buf mq_maxmsg buf mq_msgsize buf mq_curmsgs else perror mq_getattr else perror mq_open Example of mq_send The mq_send program in Example 6 3 allows you to send from 1 to 9999 messages to a queue from the command line The following command line arguments are accepted path The file pathname of the queue must be given following all options b bytes Size of each message for example b 0x200 c count Number of messages to send The default is 1 p priority Numeric priority of message to send Numbers from 0 to 32 are allowed by N mq_send Use the O_ NONB
182. cal version of the application the app defaults file for the application should specify every reasonable string resource Reference pages should identify all localizable string resources Localizers of an application provide a separate resource file for each locale that the application runs in 407 Chapter 16 Internationalizing Your Application 408 Layout Layout management is of special interest when you cannot predict how large a button or other label might be The nature of the problem of layout composition and management does not change but one must construct the layout management without full knowledge of the final appearance It s worth noting that localization efforts can be assumed to be reasonable in some sense For example X resources have always allowed a user to specify an extremely large font for buttons but applications correctly choose to let such users live with the results But it s not always that clear what is reasonable and what isn t you don t always know what will be difficult to translate succinctly in some locale So while you need not provide for all combinations of resource specifications you must make the application localizable Three main approaches to the layout problem are described below dynamic layout constant layout and localized layout Dynamic Layout Most toolkits provide form pane rowcolumn or other layout objects that calculate layout depending on the natural
183. can be used to test semop for single or multiple operations 101 Chapter 4 Mutual Exclusion Example Uses of semget The program in Example 4 3 semget invokes semget with arguments you specify on the command line k key Numeric key to identify the semaphore set required for example k 99 Default is IPC_PRIVATE p perms Access permissions to apply to a created set for example p 0664 Default is octal 0600 s setsize Number of semaphores in a created set for example s 8 The limit is 25 but feel free to experiment with larger numbers to see the return code c Use IPC_CREAT No set is created unless this is specified x Use IPC_EXCL Use with c to require that a set not exist Example 4 3 Program to Demonstrate semget semget program to test semget 2 for creating semaphores semget k lt key gt c x p lt perms gt s lt setsize gt k lt key gt the key to use default 0 IPC_PRIVATE p lt perms gt permissions to use default is 0666 s lt setsize gt size to use default is 1 G use IPC_CREAT x use IPC_EXCL K include lt sys sem h gt include lt stdio h gt key_t key int nsems 1 int perms 0600 int semflg 0 include lt unistd h gt for getopt for shmget etc include lt errno h gt errno and perror int main int argc char argv IPC_PRIVATE key setsize permissions flag val
184. ccess to locked data to write it or read access to locked data for several threads see Read Write Locks on page 298 e IRIX semaphores and locks e SVR4 semaphores Tip Synchronization between processes such as POSIX process shared mechanisms IRIX IPC and SVR4 IPC is more costly than synchronization between threads POSIX process private mechanisms So where possible use the process private mechanisms Mutexes A mutex is a software object that arbitrates the right to modify some shared variable or the right to execute a critical section of code A mutex can be owned by only one thread at a time other threads trying to acquire it wait Mutexes are intended to be lightweight and owned only for a short time Preparing Mutex Objects When a thread wants to modify a variable that it shares with other threads or execute a critical section the thread claims the associated mutex This can cause the thread to wait until it can acquire the mutex When the thread has finished using the shared variable or critical code it releases the mutex If two or more threads claim the mutex at once one acquires the mutex and continues while the others are blocked until the mutex is released A mutex has attributes that control its behavior The pthreads library contains several functions used to prepare a mutex for use These functions are summarized in Table 13 7 289 Chapter 13 Thread Level Parallelism 290 Table 13 7 Functi
185. ce file with define More commonly you will include D_BSD_COMPAT as one of the compiler flags you define in your Makefile Table 5 5 Functions for BSD Signal Handling Function Name Purpose and Operation kill 3B Send a signal to a specified process or broadcast a signal to a process group or to all processes with the same effective user ID A duplicate of a pending signal is discarded killpg 3B Send a signal to all members of a process group A duplicate of a pending signal is discarded sigvec 3 Establish a policy of default ignore or catch for a specified signal signal 3B Simplified interface to sigvec sigstack 2B Establish an alternate stack for the use of signal handling functions sigsetmask 3 Set the active signal mask sigblock 3 Add blocked signals to the active signal mask sigpause 3B Wait for specified signals to arrive Only asynchronous signal handling is supported by the BSD interface It is possible to set and interrogate the signal mask in a single operation however the signal mask type is the integer so only signal numbers 1 32 can be blocked The BSD interface does not recognize higher numbered signals Timer Facilities Timer Facilities You use timer facilities for a number of purposes to get information about program performance to make a program pause for a certain time to program an interval of time and to create a timestamp value to store with other data Timed Pauses a
186. ce one at 0x30000000 through 0x3000 Offf and the other at 0x3004 0000 through 0x3004 Offf 256 KB is 0x0004 0000 Note If two programs in the same system attempt to map different objects to the same absolute address the second attempt fails Locking and Unlocking Pages in Memory A page fault interrupts a process for many milliseconds Not only are page faults lengthy their occurrence and frequency are unpredictable A real time application cannot tolerate such interruptions The solution is to lock some or all of the pages of the address space into memory A page fault cannot occur on a locked page 23 Chapter 1 Process Address Space 24 Memory Locking Functions You can use any of the functions summarized in Table 1 2 to lock memory Table 1 2 Functions for Locking Memory Function Name Compatibility Purpose and Operation mlock 3C POSIX Lock a specified range of addresses mlockall 3C POSIX Lock the entire address space of the calling process mpin 3C IRIX Lock a specified range of addresses plock 3C SVR4 Lock all program text or all data or the entire address space Locking memory causes all pages of the specified segments to be defined before they are locked When virtual swap is in use it is possible to receive a SIGKILL exception while locking because there was not enough swap space to define all pages see Delayed and Immediate Space Definition on page 7 Locking pages in memory of course
187. chor and invalidates that cache line for every other thread It is inevitable that a queue anchor variable will be frequently invalidated However the time cost can be isolated to queue access by applying strategy 2 allocate the queue anchor in separate memory from the global status area Put a nonvolatile pointer to the queue in the status area Now the cost of fetching the queue anchor is born only by threads that access the queue If there are other items that are updated with the queue anchor such as the lock that controls exclusive access to the queue see Chapter 4 Mutual Exclusion place those items adjacent to the queue anchor so that all are in the same cache line strategy 4 However if there are two queues that are updated at unrelated times place each in its own cache line strategy 3 Using Origin2000 Nonuniform Memory The locks semaphores and message queues that are used to synchronize threads see Types of Interprocess Communication Available on page 46 are global variables that must be updated by any CPU that uses them It is best to assume that such objects are accessed at memory speeds Two things can be done to reduce contention e Minimize contention for locks and semaphores through algorithmic design In particular use more rather than fewer semaphores and make each stand for the smallest possible resource Of course this makes it more difficult to avoid deadlocks e Never place unrelated sy
188. cify any type less than or equal 157 Chapter 6 Message Queues 158 Example Programs The following programs demonstrate the use of SVR4 message queues e Example 6 5 on page 161 demonstrates the use of msgget to create or access a queue e Example 6 6 on page 164 demonstrates the use of msgctl to query or modify a queue e Example 6 7 on page 167 demonstrates the use of msgsnd to put messages onto a queue e Example 6 8 on page 170 demonstrates the use of msgrev to take messages from a queue The four example programs have a consistent design and use consistent command line argument letters Each accepts optional arguments that allow you to exercise all the features of one function including most error return codes The following is a simple example of use First ipcs is used to show no queues exist ipes q IPC status from dev kmem as of Wed Jun 12 10 36 38 1996 T ID KEY MODE OWNER GROUP Message Queues Then a queue is created with key 9 and ipcs used to verify the operation msgget k 9 c msqid 0x0032 owner 1110 20 perms 100600 max bytes 32768 0 msgs 0 bytes on queue ipcs q IPC status from dev kmem as of Thu Jun 20 09 32 25 1996 AR ID KEY MODE OWNER GROUP Message Queues q 50 0x00000009 rw cortesi user The use of the IPC_EXCL flag is tested msgget k 9 c x msgget File exists System V Message Queues A message is sent to the que
189. ckf 189 Setting Mandatory Locking Permission Bits 191 Initializing Asynchronous I O 200 Polling for Asynchronous Completion 203 Set of Functions to Schedule Asynchronous I O 206 Source Code of aiocat 211 Source of Direct I O Example 232 Function to Create a Real time File 239 Partial Code to Manage a Pool of Processes 269 One Time Initialization 281 Function to Set Own Priority 288 Use of Condition Variables 295 Find Number of Bytes in an MB Character 351 Counting MB Characters Without Conversion 352 Reading an XPG 4 Catalog 373 Internationalized Code 382 Initializing Xlib fora Locale 385 Creating a Fontset 387 Opening anIM 396 Finding What a Client Can Do 400 Setting the Desired IM Style 401 Creating an Input Context With XCreateIC 403 Using the IC 404 Event Loop 404 KeyPress Event 406 List of Figures Figure 1 1 Figure 15 1 Figure 15 2 Figure 16 1 Figure 16 2 Segments With a Fixed Offset Relationship 22 X Window System Font Name Example 314 Sample Display From xfd 317 Root Window Input 397 Off the Spot Input 398 xxvii List of Tables Table i Table ii Table 1 1 Table 1 2 Table 1 3 Table 2 1 Table 2 2 Table 3 1 Table 3 2 Table 3 3 Table 3 4 Table 3 5 Table 3 6 Table 3 7 Table 4 1 Table 4 2 Table 4 3 Table 4 4 Table 4 5 Table 4 6 Table 4 7 Table 4 8 Table 4 9 Table 4 10 Table 4 11 Table 4 12 Table 4 13 Books for Further Reading in IRIX Development xxxiv Typog
190. client should not intersect this rectangle max_logical_extent is used to compute interline spacing and the minimum amount of space needed for a given number of characters Here are descriptions of a few of the new extents related functions consult the appropriate reference pages for details e XExtentsOfFontSet returns an XFontSetExtents structure for a fontset e XmbTextEscapement and XwcTextEscapement take a string and return the distance in pixels in the current drawing direction to the origin of the next character after the string if the string were drawn Escapement is always positive regardless of direction e XmbTextExtents and XwcTextExtents take a string and return information detailing the overall rectangle bounding the string s image and the space the string occupies for spacing purposes e XmbTextPerCharExtents and XwcTextPerCharExtents take a string and return ink and logical extents for each character in the string Use this for redrawing portions of strings or for word justification If the fontset might include context dependent drawing the client cannot assume that it can redraw individual characters and get the same rendering e XContextDependentDrawing returns a Boolean telling whether a fontset might include context dependent drawing 389 Chapter 16 Internationalizing Your Application Internationalization Support in Motif 390 Your applications can use Motif s internationalizati
191. cond signal is discarded In other words at most one signal of a given number can normally be pending for a process 117 Chapter 5 Signalling Events 118 In the POSIX interface you can use one particular function sigqueue to send a signal that is queued regardless of how many signals of the same number are already pending Signal Handling Policies You can specify one of three policies for handling an unblocked signal You set the policy for each signal number individually Default Handling Initially all signals receive default handling This means that when a signal arrives and is not blocked it causes the default action listed in Table 5 1 In many cases the default action is to ignore the signal that is to silently discard it In other cases the default action is to terminate the program or to terminate it with a dump Each signal interface gives you a way to specify non default handling or a specified signal or to return a signal to default handling Ignoring Signals You can request that a specified signal be ignored You would do this when the signal is not meaningful to your program and the default action is not what you wish For example in a noninteractive program you might set Ignore handling for SIGHUP the default action is to terminate Catching Signals You can request that a signal be caught and handled asynchronously at the moment it arrives You specify that a signal should be caught by specify
192. cs endif pch gt etime clock do read and write read and write Set up the aiocb for a read queue it and wait for it pab gt aio_fildes pch gt fd pab gt aio_offset pch gt inbase pab gt aio_nbytes BLOCKSIZE if ret aio_read pab break unable to schedule a read ret inWait0 pch if ret break nonzero read completion status get the result of the read call the count of bytes read Since aio_error returned 0 the count is nonnegative It could be 0 or less than BLOCKSIZE indicating EOF aa bytes aio_return pab actual read result if bytes break no need to write a last block of 0 pch gt inbase bytes where to read next time Set up the aiocb for a write queue it and wait for it a pab gt aio_fildes outFD pab gt aio_nbytes bytes pab gt aio_offset pch gt outbase if ret aio_write pab break ret inWait0 pch if ret break pch gt outbase bytes where to write next time while ret amp amp bytes BLOCKSIZE 220 Asynchronous I O Example The loop is complete If no errors so far use aio_fsync to ensure that output is complete This requires waiting yet again x if ret if ret aio_fsync O_SYNC pab ret inWait0O pch Flag any errors for the parent proc If none count elapsed time xy if ret errors lse pch gt etim
193. ction describes styles and their naming Root Window The Root Window style has a pre edit area and a status area ina window owned by the IM as a descendant of the root The application does not manage the pre edit data the pre edit area the status data or the status area Everything is left to the input method to do in its own window as illustrated in Figure 16 1 Main body of window text input occurs here Application window root window Status Pre edit information f IM window Figure 16 1 Root Window Input 397 Chapter 16 Internationalizing Your Application 398 Off the Spot The Off the Spot style places a pre edit area and a status area in the window being used usually in reserved space away from the place where input appears The application manages the pre edit area and status area but allows the IM to update the data there The application provides information regarding foreground and background colors fonts and so on A window using Off the Spot input style might look like that shown in Figure 16 2 Application window Main body of window text input occurs here Status Pre edit information root window Figure 16 2 Off the Spot Input Over the Spot The Over the Spot style involves the IM creating a small pre edit window over the point of insertion The window is owned and managed by the IM as a descendant of the root but it gives the user the impression that input is being entered in t
194. cutes or the number of page faults it encounters and so on No recompilation or relinking is required and the program runs only fractionally slower than normal Using perfex you can discover approximately how much time a program or a single thread of a program loses to cache invalidations and how many invalidations there were This allows you to easily distinguish cache contention from other performance problems 35 Chapter 1 Process Address Space 36 Correcting Cache Contention Problems Cache contention is corrected by changing the layout of data in the source program In general terms the available strategies are these 1 Minimize the number of variables that are accessed by more than one thread 2 Segregate nonvolatile data items into different cache lines from volatile items 3 Isolate volatile items that are not related into separate cache lines to eliminate false sharing 4 When volatile items are updated together group them into single cache lines A common design for a large program is to define a block of global status variables that is visible to all parallel threads In the normal course of the program every CPU caches all or most of such a common area Read only access does no harm but if the items in the block are volatile contention occurs For example a global area might contain the anchor for a LIFO queue of some kind Every time a thread puts or takes an item from the queue it updates the queue an
195. d g lt gid gt new group id numeric for msg_perm gid include lt sys msg h gt msg queue stuff ipc h types h include lt errno include lt unistd h gt for getopt h gt errno and perror h gt include lt stdio int main int argc char argv key_t key int msgid long perms long bytes long uid 1 long gid 1 key for msgget siy specified or received msg queue id 1L 1L is not valid for any of these I L L struct msqid_ds buf int c while 1 c getopt argc argv k i b p u g switch c case k key key key_t strtoul optarg NULL 0 break case i id msqid int strtoul optarg NULL 0 break case p permissions perms strtoul optarg NULL 0 break case b bytes bytes strtoul optarg NULL 0 break case tuti uid uid strtoul optarg NULL 0 break System V Message Queues case g Gid gid strtoul optarg NULL 0 break default unknown or missing argument return 1 if 1 msgid no id given try key msqid msgget key 0 if 1 msqid if 1 msgctl msqid IPC_STAT amp buf if perms 1L bytes 1L uid 1L gid 11L put new values in buf fields as requested if perms 1L buf msg_perm
196. d before There are two essential differences the XFilterEvent and X LookupString routines Using XFilterEvent Every event received by your application should be fed to the IM via XFilterEvent which returns a value telling you whether or not to disregard the event IMs asks you to disregard the event if they have extracted the data and plan on giving it to you later possibly in some other form All events not just KeyPress and KeyRelease events go to XFilterEvent If you compacted the event processing into a single routine a typical event loop would look something like the code in Example 16 12 Example 16 12 Event Loop Xevent event while TRUE XNextEvent dpy amp event if XFilterEvent amp event None continue DealWithEvent amp event 404 Translating User Input Using XLookupString XwcLookupString and XmbLookupString When using an input method you should replace calls to XLookupString with calls to XwcLookupString or XmbLookupString The MB and WC versions have very similar interfaces The examples below arbitrarily use XmbLookupString but apply to both versions There are two new situations to deal with 1 The string returned may be long 2 There may be an interesting keysym returned an interesting set of characters returned both or neither Dealing with the former is a matter of maintaining an arena as in Example 16 13 To tell the applicatio
197. d in Multibyte Characters Table 16 11 lists some of these standard character sets Note that some of these character sets have multiple associated codesets usually designated by appending the year the codeset was adopted to the character set name For example JIS X 208 1983 is different from JIS X 208 1990 Table 16 11 Character Sets for Asian Languages Language Character Set Standards Support Japanese JIS X 0201 1976 0 Katakana JIS X 0208 1983 0 Kanji kana Latin Greek Cyrillic symbols others JIS X 0212 1990 0 Supplemental kanji others Chinese GB 2312 1980 0 Korean KSC 5601 1987 0 Hangul Taiwan CNS 11643 EUC EUC is Extended UNIX Code an encoding methodology that supports concurrent use of four codesets in one encoding It employs two special shift state bytes ssl 0x8e ss2 0x8f These are used to identify codesets within a string The EUC encoding scheme uses the following patterns to indicate which codeset is in use at any given time Codeset 0 Oxxxxxxx Codeset 1 1XXXXXXX 1XXXXXXX Codeset 2 ssl 1XXXXXXX 1XXXXXXX Codeset 3 ss2 1xxxxxxx 1XXXXXXX Popular Encodings So if ss appears in a string it means that the next character however many bytes long it is should be interpreted as a character from codeset 2 If there are multiple characters in a row from codeset 2 each one is preceded by ss1 Similarly ss2 indicates that the following character belong
198. d record locks Part III Advanced File Control describes advanced uses of disk files file locking asynchronous I O direct I O and guaranteed rate I O Part IV Models of Parallel Computation gives an overview of the different ways you can specify parallel execution in Silicon Graphics systems Part V Working With Fonts discusses typography and font use on Silicon Graphics computers and describes the Font Manager library Part VI Internationalizing Your Application explains how to create an application that can be adapted for use in different countries Appendix A ISO 3166 Country Names and Abbreviations lists country codes for use with internationalization and localization xxxiii About This Manual What You Should Know Before Reading This Manual This manual assumes that you are writing an application that executes under IRIX version 6 2 or later and that you are familiar with the programming conventions of UNIX in general and IRIX in particular All examples are in the C language although the descriptions are valid for C or any other language that provides access to IRIX kernel functions such as Silicon Graphics Ada95 or MIPSpro Fortran 90 Other Useful References In addition to this manual which covers specific IRIX features you will need to refer to Silicon Graphics manuals that describe compilers and programming languages Some of the most useful are listed in Table i
199. d that requests the I O is blocked until the I O has completed The effects are different for input and for output About Synchronous Input The normal sequence of operations for input is as follows 1 ATEOS OLT HS A process invokes the system function read either directly or indirectly for example by accessing a new page of a memory mapped file or by calling a library function that calls read The kernel operating under the identity of the calling process enters the read entry point of a device driver The device driver initiates an input operation and blocks the calling process for example by waiting on a semaphore in the kernel address space The kernel schedules another process to use the CPU Later the device completes the input operation and causes a hardware interrupt The kernel interrupt handler enters the device driver interrupt entry point The device driver finding that the data has been received unblocks the sleeping process for example by posting a semaphore The kernel notes that the blocked process can now run 195 Chapter 8 Using Asynchronous I O 196 9 Then or perhaps later depending on scheduling priorities the kernel schedules the process to run on some CPU 10 The unblocked process exits the read system call and returns to user code the read being complete During steps 4 8 the process that requested input is blocked The duration of the delay is unpredictable For exam
200. dFunc toCall set address of func to exec theSproc gt callArg callWith set argument to pass theSproc gt sprocDone done set sema to post on completion usvsema theSproc gt sprocWait wake up sleeping process Parallelism in Real Time Applications In real time programs such as aircraft or vehicle simulators separate processes are used to divide the work of the simulation and distribute it onto multiple CPUs In these demanding applications the programmer frequently uses IRIX facilities to e reserve one or more CPUs of a multiprocessor for exclusive use by the application e isolate the reserved CPUs from all interrupts e assign specific processes to execute on specific reserved CPUs These facilities are described in detail in the REACT Real Time Programmer s Guide 007 2499 nnn Also covered in that book is the use of the Frame Scheduler an alternate process scheduler The normal process scheduling algorithm of the IRIX kernel attempts to keep all CPUs busy and to keep all processes advancing in a fair manner This algorithm is in conflict with the stringent needs of a real time program which needs to dedicate predictable amounts of hardware capacity to its processes without regard to fairness The Frame Scheduler seizes one or more CPUs of a multiprocessor isolates them and executes a specified set of processes on each CPU in strict rotation The Frame Scheduler has much lower overhead than the
201. der to minimize the overhead of polling for elapsed timers the kernel did not allow normal processes to ask for timer intervals with fine granularity sub millisecond precision Only processes that executed under real time scheduling priority could ask for precise timer intervals Starting with IRIX 6 2 any process can request a timer interval with any precision If this support is misused it is possible to cause performance problems For example a process can set up a repeating timer at an interval so short that one CPU is monopolized by setting and handling that timer POSIX Timers IRIX supports the time and timer facilities specified by IEEE standard 1003 1b 1993 commonly called POSIX timers This timer interface is the most complete robust and portable and is recommended for all new applications The functions it includes for time measurement are summarized in Table 5 8 129 Chapter 5 Signalling Events 130 Table 5 8 POSIX Time Management Functions Function Name Purpose and Operation time 2 times 2 clock_gettime 2 clock_getres 2 Return a time_t value containing the count of seconds elapsed since 00 00 00 UTC January 1 1970 Return user and system execution time consumption for the calling process and its terminated child processes Return the instantaneous reading of one of two clocks the system time CLOCK_REALTIME or the hardware cycle counter CLOCK_SGI_CYCLE Return the precisi
202. ding the decimal radix inappropriately called decimal_point the grouping separator inappropriately called thousands_sep the grouping rules and a great deal of monetary formatting information The localeconv function leaves actual use of formatting information other than the decimal radix to the application Cultural Items Using strfmon The strfmon function detailed in the strfmon 3S reference page is new with IRIX version 6 2 Like sprintf strfmon takes an output area a format string that contains conversion specifications and one or more argument values to be converted It creates an output string containing fixed data and converted values Only two conversion types are supported i to convert a double value to international currency representation and n to convert a double value to national currency representation You can use strfmon to format currency values as strings and then use printf or other functions to write the formatted strings Formatting Dates and Times All of these dates can mean the same thing to different people 92 1 4 4 1 92 1 4 92 All of these can mean the same time to different people 2 30 PM 14 30 14h30 Dates and times can be easily formatted by using strftime which gives a host of options for displaying locale specific dates and times The ascftime and cftime functions give further options but should be avoided because they do not conform to ANSI and XPG 4 specif
203. ditArea XIMStatusArea Over the Spot XIMPreeditPosition XIMStatusArea On the Spot XIMPreeditCallbacks XIMStatusCallbacks For example if you wanted a style variable to match an Over the Spot IM style you could write XIMStyle over XIMPreeditPosition XIMStatusArea If an IM returns XIMStatusNone not to be confused with XIMStatusNothing it means the IM will not supply status information Using Styles An input method supports one or more styles It s up to the application to find a style that is supported by both the IM and the application If several exist the application must choose If none exist the application is in trouble 399 Chapter 16 Internationalizing Your Application 400 Input Contexts ICs An input method may be serving multiple clients or one client with multiple windows or one client with multiple input styles on one window The specification of style and client IM communication is done via input contexts An input context is simply a collection of parameters that together describe how to go about receiving and examining input under a given set of circumstances To set up and use an input context Decide what styles your application can support Query the IM to find out what styles it supports Find a match Create the IC 1 2 3 4 Determine information that the IC needs in order to work with your application 5 6 Employ the IC Find an IM Style The IM may be able to su
204. e Scheduling Pthreads on page 286 Initializing Static Data Your program may use static data that should be initialized exactly once The code can be entered by multiple threads and might be entered concurrently How can you ensure that only one thread will perform the initialization One answer is to create a variable of type pthread_once_t statically initialized to the value PTHREAD_ONCE_INIT Call pthread_once passing the addresses of the variable and of an initialization function The pthreads library ensures that the initialization function is called only once and that any other threads calling pthread_once for this variable wait until the first thread completes the initialization function See Example 13 1 Example 13 1 One Time Initialization pthread_once_t first_time_flag PTHREAD_ONCE_INIT elaborate_struct_t uninitialized thing to initialize void elaborate_initializer void function to do it int subroutine pthread_once amp first_time_flag elaborate_initializer Setting Event Handlers A thread can establish functions that are called when it terminates and when the process forks 281 Chapter 13 Thread Level Parallelism 282 Call pthread_cleanup_push to register a function that is to be called in the event that the current thread terminates either by exiting or by cancellation Call pthread_cleanup_pop to retract this registration and optionally to call t
205. e clock pch gt etime if DO_SPROCS Rendezvous with the rest of the family then quit KY barrier convene nprocs endif return end inProcl BRK KK KR RR RR RRR RA RR RRA RAR A A A A A A A A A A A I A inProcl uses aio_suspend to await the completion of each operation Otherwise it is the same as inProc0 above A int inWaitl child_t pch int ret aiocb_t susplist 1 list of 1 aiocbh for aio_suspend susplist 0 amp pch gt ach Note aio h declares the lst argument of aio_suspend as const The C compiler requires the actual parameter to match in type so the list we pass must either be declared const aiocb_t or must be cast to that else cc gives a warning The cast in the following statement is only to avoid this warning ret aio_suspend const aiocb_t susplist 1 NULL return ret void inProcl void arg size_t stk 221 Chapter 8 Using Asynchronous I O child_t pch arg starting arg is gt child_t for my file aiocb_t pab amp pch gt ach base address of the aiocb_t in child t int ret as long as this is 0 all is ok int bytes bytes read on each input Initialize no signals or callbacks needed KN pab gt aio_sigevent sigev_notify SIGEV_NONE pab gt aio_buf pch gt buffer always the same if DO_SPROCS Wait f
206. e When the other words are not related to the new data false sharing occurs that is variables are invalidated and have to be reloaded from memory merely by the accident of their address with no logical need These cache contention issues are not new to the Origin architecture they arise in any multiprocessor that supports cache coherency Detecting Cache Contention The first problem with cache contention is to recognize that it is occurring In earlier systems you diagnosed cache contention by elimination Now you can use software tools and the hardware features of the MIPS R10000 CPU to detect it directly The R10000 includes hardware registers that can count a variety of discrete events during execution at no performance cost The R10000 can count individual clock cycles numbers of loads stores and floating point instructions executed as well as cache invalidation events The IRIX kernel contains support for virtualizing the R10000 counter registers so that each IRIX process appears to have its own set of counters just as the kernel ensures that each process has its own unique set of other machine register contents Included with IRIX is the perfex profiling tool see the perfex 1 reference page It executes a specified program after setting up the kernel to count the events you specify At the end of the test run perfex displays the profile of counts You can use perfex to count the number of instructions a program exe
207. e Laos LA Lebanon LB Lesotho LS Liberia LR Libya LY Liechtenstein LI Luxembourg LU Macau MO Madagascar MG Malawi MW Malaysia MY Maldives MV Mali ML Malta MT Marshall Islands MH Martinique MQ Mauritania MR Mauritius MU Mexico MX Micronesia FM Monaco MC Mongolia MN Montserrat MS Morocco MA Mozambique MZ Namibia NA Nauru NR Nepal NP Netherlands NL Netherlands AN Antilles Neutral Zone NT New Caledonia NC New Zealand NZ Nicaragua NI Niger NE Nigeria NG Niue NU Norfolk Island NF Northern Mariana MP Islands Norway NO Oman OM Pakistan PK Palau PW Panama PA Pangaea GE Papua New PG Paraguay PY Peru PE Guinea Philippines PH Pitcairn PN Poland PL Portugal PT Puerto Rico PR Qatar QA Quebec QC Reunion RE Romania RO Rwanda RW Saint Kitts and KN Saint Lucia LC Nevis Saint Vincentand VC Samoa WS San Marino SM the Grenadines 417 Appendix A ISO 3166 Country Names and Abbreviations 418 Table A 1 ISO 3166 Country Codes continued Country Name Code Country Name Code Country Name Code Sao Tome and ST Saudi Arabia SA Senegal SN Principe Seychelles SC Sierra Leone SL Singapore SG Solomon Islands SB Somalia SO South Africa ZA Spain ES Sri Lanka LK St Helena SH St Pierre and PM Sudan SD Suriname SR Miquelon Svalbard and Jan SJ Swaziland SZ Sweden SE Mayen Islands Switzerland CH Syrian Arab SY Taiwan TW Republic Tanzania TZ Thailand TH Togo TG Tokelau TK Tonga TO Trinidad and TT Tobago Tunisia TN Turkey TR Turks and C
208. e Cray or Silicon Graphics system use SHMEM For the highest performance in an Array system linked with HIPPI use MPI Use PVM only when compatibility or portability is an overriding consideration Choosing Between MPI and PVM Choosing Between MPI and PVM When your program must be able to use the resources of multiple systems you choose between MPI and PVM In many ways MPI and PVM are similar e Each is designed specified and implemented by third parties that have no direct interest in selling hardware e Support for each is available over the Internet at low or no cost e Each defines portable high level functions that are used by a group of processes to make contact and exchange data without having to be aware of the communication medium e Each supports C and Fortran 77 e Each provides for automatic conversion between different representations of the same kind of data so that processes can be distributed over a heterogeneous computer network Another difference between MPI and PVM is in the support for the topology the interconnect pattern grid torus or tree of the communicating processes In MPI the group size and topology are fixed when the group is created This permits low overhead group operations The lack of run time flexibility is not usually a problem because the topology is normally inherent in the algorithmic design In PVM group composition is dynamic which requires the use of a group server
209. e Locks 299 14 Message Passing Parallelism 301 Choosing a Message Passing Model 302 xvi Contents Choosing Between MPI and PVM 303 Differences Between PVM and MPI 304 15 Working With Fonts 309 Font Basics 310 Terminology 310 Typography 310 Character 311 Font 311 Font Family or Typeface 311 How Resolution Affects Font Size 312 Font Names 313 Writing Programs That Need to Use Fonts 314 Using Fonts With the X Window System 315 Listing and Viewing Fonts 315 Getting a List of Font Names and Font Aliases 315 Viewing Fonts 316 Getting the Current X Font Path 318 Changing the X Font Path 318 Installing and Adding Font and Font Metric Files 319 Locations of Font and Font Metric Files 319 Conventions for Bitmap Font Filenames 321 Creating Font Aliases 321 Adding Font and Font Metric Files 322 Adding a Bitmap Font 322 Adding an Outline Font 326 Adding a Font Metric File 328 Downloading a Type 1 Font to a PostScript Printer 329 xvii Contents 16 Internationalizing Your Application 333 Overview of Internationalization 334 Some Definitions of Internationalization 335 Locale 335 Internationalization i118n 335 Localization 110n 335 Nationalized Software 336 Multilingual Software 336 Areas of Concern in Internationalizing Software 336 Standards 337 Internationalizing Your Application The Basic Steps 337 Additional Reading on Internationalization 339 Using Locales 340 Setting the Current Locale 340 Using Locale Catego
210. e O_DIRECT you are required to transfer data in quantities that are multiples of the disk blocksize aligned on blocksize boundaries The requirements for O_DIRECT use are documented in the open 2 and fcntl 2 reference pages An O_DIRECT read or write is synchronous control does not return until the disk operation is complete Also an O_DIRECT read call always causes disk input there is no input cache However you can open a file O_DIRECT and use the file descriptor for asynchronous I O so that the delays are taken by an asynchronous thread see About Asynchronous I O on page 196 Direct I O is required when you use guaranteed rate I O see Using Guaranteed Rate I O on page 236 Direct I O Example The program in Example 9 1 allows you to experiment and compare buffered output synchronized output and direct output An example of using it might resemble this gt timex dirio o var tmp dout m b b 4096 n 100 real 0 10 user 0 01 sys 0 02 gt timex dirio o var tmp dout m d b 4096 n 100 real 135 user 0 01 sys 0 06 gt timex dirio o var tmp dout m s b 4096 n 100 real 3 43 user 0 01 sys 0 09 231 Chapter 9 High Performance File I O Example 9 1 Source of Direct I O Example dirio program to test and demonstrate direct I O dirio o outfile m b s d b bsize n recs i o outfile output file pathname default STEMPDIR dirio out m b s d file
211. e are characters commonly used in other areas of the world that are not present on most USA keyboards So methods have been invented that provide for input of almost any known character on even the most naive keyboards These schemes are referred to as input methods IMs 391 Chapter 16 Internationalizing Your Application 392 Input methods vary significantly in design use and behavior but there is a single API that developers use to access them The object is for the application simply to ask for an IM and let the system check the locale and choose the appropriate IM Some IMs are complex others are very simple The API is designed to be a low level interface like Xlib Usually only toolkit text object authors must deal with the IM interfaces However some applications developers are unable to use toolkit objects so the concepts are described here Reuse Sample Code A sample program demonstrating some of the concepts in this section is given in Chapter 11 of the Xlib Programming Manual Volume One Looking carefully at that code may be easier than starting from scratch GL Input The old GL function qdevice has a hard coded view of a keyboard see usr include gl device h for details Some flexibility particularly for Europe is available if you queue KEYBD instead of individual keys but the GL has no general solution to non ASCII input There is no supported way to input Chinese for instance to the old GL OpenGL
212. e certain that operations are done in sequence is to schedule them one at a time waiting for each one to complete Asynchronous I O Example Asynchronous I O Example The following source displays a highly artificial program whose purpose is to exercise most options of asynchronous I O The program syntax is aiocat o outfile a 0 1 2 3 infilename The actual output of the program is the concatenation of all the one or more files infilename written to the file outfile The default outfile is STEMPDIR aiocat out In effect the program is an overcomplicated version of the standard cat command When you compile it with the variable DO_SPROCS defined as 1 the program creates one process for each infilename Each of these processes uses asynchronous I O requests to read its corresponding input file and to write that data to the correct offset in outfile After all the files have been read and written the program reports the CPU time charged for each file and the effective data transfer rate in bytes per microsecond The a parameter specifies which of four methods is used to wait for I O completion a 0 Poll for completion with aio_error a 1 Wait for completion with aio_suspend a 2 Wait on a semaphore posted from a signal handler a 3 Wait on a semaphore posted from a callback routine Execution of aiocat can resemble the following from an Origin2000 with 8 CPUs gt ls l incat rwxr xr x 1 cor
213. e child process The argument which must be declared void to match the sproc prototype is the oneSproc structure that represents this process The contents of that struct in particular sprocWait are initialized by the parent ef void childBody void theSprocAsVoid struct oneSproc mySproc struct oneSproc theSprocAsVoid here one could establish signal handlers etc for 77 sprocSleep mySproc wait for work to do mySproc gt calledFunc mySproc gt callArg do the work if mySproc gt sprocDone if a completion sema is given usvsema mySproc gt sprocDone post it Acquire a oneSproc structure from the ready list waiting if necessary Called by the master process as part of dispatching a sproc struct oneSproc getSproc struct oneSproc theSproc uspsema readySprocs wait until at least 1 sproc is free ussetlock sprocListLock acquire exclusive rights to sprocList theSproc sprochist get address of first free oneSproc sprocList theSproc gt next make next in list the head of list usunsetlock sprocListLock release sprocList return theSproc Start a function going asynchronously Called by master process void execFunc workFunc toCall void callWith usema_t done Parallelism in Real Time Applications struct oneSproc theSproc getSproc theSproc gt calle
214. e device that you open and pass as the file descriptor determines the bus address space A16 A24 or A32 The values you specify in off and len must agree with accessible locations in that VME bus space A read or write to a location in the mapped segment causes a call to the read or write entry of the kernel device driver for VME PIO An attempt to read or write an invalid location in the bus address space causes a SIGBUS exception to all processes that have mapped the device Note On the CHALLENGE and Onyx hardware PIO reads and writes are asynchronous Following an invalid read or write as much as 10 milliseconds can elapse before the SIGBUS signal is raised For a detailed discussion of VME PIO see the IRIX Device Driver Programmer s Guide Note Mapping of devices through mmap is an IRIX feature that is not defined by POSIX standard Do not use the POSIX shm_open function with device special files Choosing a Segment Address Normally there is no need to map a segment to any particular virtual address You specify addr as 0 and IRIX picks an unused virtual address This is the usual method and the recommended one You can specify a nonzero value in addr to request a particular base address for the new segment You specify MAP_FIXED in flags to say that addr is an absolute requirement and that the segment must begin at addr or not be created If you omit MAP_FIXED mmap takes a nonzero addr as a suggestion only Segments at
215. e inherently different for the two libraries owing for example to the concept of dynamic groups in PVM Hence the process of converting a PVM program into an MPI program can be straightforward or complicated depending on the particular PVM calls in the program and how they are used For many PVM programs conversion is straightforward In addition to a message passing library PVM also provides the concept of a parallel virtual machine session A user starts this session before invoking any PVM programs in other words PVM provides the means to establish a parallel environment from which a user invokes a parallel program Additionally PVM includes a console which is useful for monitoring and controlling the states of the machines in the virtual machine and the state of execution of a PVM job Most PVM console commands have corresponding library calls The MPI standard does not provide mechanisms for specifying the initial allocation of processes to an MPI computation and their binding to physical processors Mechanisms to do so at load time or run time are left to individual vendor implementations However this difference between the two paradigms is not by itself significant for most programs and should not affect the port from PVM to MPI Choosing Between MPI and PVM The chief differences between the current versions of PVM and MPI libraries are as follows PVM supports dynamic spawning of tasks whereas MPI does not PVM s
216. e is unlocked This feature is not available through the POSIX and SVR4 interfaces Locked pages of an address space are unlocked when the last process using the address space terminates Locked pages of a mapped segment are unlocked when the last process that mapped the segment unmaps it or terminates Additional Memory Features Your program can work with the IRIX memory manager to change the handling of the address space 27 Chapter 1 Process Address Space 28 Changing Memory Protection You can change the memory protection of specified pages using mprotect see the mprotect 2 reference page For a segment that contains a whole number of pages you can specify protection of these types Read only By making pages read only you cause a SIGSEGV signal to be generated in any process that tries to modify them You could do this as a debugging measure to trap an intermittent program error You can change read only pages back to read write Read write You can put read write protection on pages of program text but this is bad idea except in unusual cases For example a debugging tool makes text pages read write in order to set breakpoints Executable Normal data pages cannot be executed This is a protection against program errors wild branches into data are trapped quickly If your program constructs executable code or reads it from a file the protection must be changed to executable before the code can be executed
217. e modifier list argument is a null terminated string containing zero or more concatenated expressions of this form category value For example if you want to connect Input Method Server xwnmo set modifiers _XWNMO as follows XSetLocaleModifiers im _XWNMO Or set environment variable XMODIFIERS to the string im _xWNMo and execute XSetLocaleModifiers Note The library routines are not prepared for the possibility of XSupportsLocale succeeding and XOpenIM failing so it s up to application developers to deal with such an eventuality This circumstance could occur for example if the IM died after XSupportsLocale was called This topic is under some debate in the MIT X consortium If XSetLocaleModifiers is wrong XOpenIM will fail Translating User Input Most of the complexity associated with IM use comes from configuring an input context to work with the IM Input contexts are discussed in Input Contexts ICs on page 400 To close an input method call XCloseIM IM Styles If the application requests it an input method can often supply status information about itself For example a Japanese IM may be able to indicate whether it is in Japanese input mode or romaji input mode An input method can also supply pre edit information partial feedback about characters in the process of being composed The way an IM deals with status and pre edit information is referred to as an IM style This se
218. e same time period to the same subvolume drives or controllers Each reservation consumes some part of the total capacity 239 Chapter 9 High Performance File I O 240 When XFS predicts that the guaranteed rate can be met it accepts the reservation Over the reservation period the available bandwidth from the disk is reduced by the promised rate Other processes can place reservations against any capacity that remains If XFS predicts that the guaranteed rate cannot be met at some time in the reservation period XFS returns the maximum data rate it could supply The program can reissue the request for that available rate However this is a new request that is evaluated afresh During the reservation period the process can use read and write to transfer up to the guaranteed number of bytes in each time unit XFS raises the priority of requests as needed in order to ensure that the transfers take place However a request that would transfer more than the promised number of bytes within a 1 second unit is blocked until the start of the next time unit Releasing a Guarantee A guarantee ends under three circumstances e when the process calls grio_unreserve_bw see the grio_unreserve_bw 3X reference page e when the requested duration expires e when all file descriptors held by the requesting process that refer to the guaranteed file are closed an exception is discussed in the next topic When a guarantee ends the g
219. e size ownership and permissions of an existing shared segment using ls I You can dump its contents with a command such as od X You can remove it with rm Shared Object Open Flags The flags you pass to shm_open control its actions as follows O_RDONLY Access can be used only for reading O_RDWR Access can be read write however you can enforce read only access when calling mmap O_CREAT If the object does not exist create it O_TRUNC If the object does exist and O_RDWR is specified truncate it to zero length O_EXCL If the object does exist and O_CREAT is specified return the EEXIST error code The flags have the same meaning when opening a disk file with open However a number of other flags allowed by open are not relevant to shared memory objects You can use the combination O_CREAT O_EXCL to ensure that only one process initializes a shared object Shared Object Access Mode The access mode that you specify when creating an object governs the users and groups that can open the object later exactly as with a disk file POSIX Shared Memory Operations Using the Shared Object File Descriptor The value returned by shm_open is a file descriptor and you can use it as such for example you can apply the dup function to make a copy of it You can also use it as an argument to fentl but most of the features of fentl are irrelevant to a shared memory object See the dup 2 and fcntl 2 reference pa
220. e the new portion of the file maps to a different additional memory segment The old segment is replaced with a new segment at the same address now containing data from a different offset in the file Note Each time you replace a segment with mmap the previous segment is discarded The new segment is not locked in memory even if the old segment was locked File Permissions Access to a file for mapping is controlled by the same file permissions that control I O to the file The protection in prot must agree with the file permissions For example if the file is read only to the process mmap does not allow prot to specify write or execute access Note When a program runs with superuser privilege for other reasons file permissions are not a protection against accidental updates NFS Considerations The file that is mapped can be local to the machine or can be mounted by NFS In either case be aware that changes to the file are buffered and are not immediately reflected on disk Use msync to force modified pages of a segment to be written to disk see Synchronizing the Backing Store on page 28 17 Chapter 1 Process Address Space 18 If IRIX needs to read a page of a mapped NFS mounted file and an NFS error occurs for example because the file server has gone down the error is reflected to your program as a SIGBUS exception Caution When two or more processes in the same system map an NFS mounted file
221. ecute at the same time when possible 267 Chapter 12 Process Level Parallelism 268 Note Through IRIX 6 2 schedctl also supported a scheduling mode called deadline scheduling This scheduling mode is being removed and will not be supported in the future Do not design a program based on the use of deadline scheduling Controlling Scheduling With POSIX Functions The POSIX compliant functions to control process scheduling are summarized in Table 12 4 Table 12 4 POSIX Functions for Scheduling Function Name Purpose and Operation sched_getparam 2 Query and change the POSIX scheduling priority of a process sched_setparam 2 sched_getscheduler 2 Query and change the POSIX scheduling policy and priority of a sched_setscheduler 2 process sched_get_priority_max 2 Query the maximum most use of CPU and minimum least use sched_get_priority_min 2 priority numbers for use with sched_getparam sched_get_rr_interval 2 Query the timeslice interval of the round robin scheduling policy sched_yield 2 Let other processes of the same priority execute Use the functions sched_get_priority_max and sched_get_priority_min to get the ranges of priority numbers you can use Use sched_setparam to change priorities POSIX dispatching priorities are nondegrading Note that in a program that links with the pthreads library these same function names are library functions that return thread scheduling priority numbe
222. ed by working with a WC string then converting back Getting the length without performing the conversion is straightforward but not as simple mbtowc converts one character and returns the number of bytes used but returns the same information without conversion if a NULL is passed as the address of the WC destination Thus len mblen pStr n is equivalent to len mbtowc wchar_t NULL pStr n 351 Chapter 16 Internationalizing Your Application 352 In fact mblen calls mbtowc to perform its count Therefore counting characters in an MB string without converting would look like the code in Example 16 2 Example 16 2 Counting MB Characters Without Conversion int cLen char tStr pStr numChars 0 cLen mbtowc wchar_t NULL tStr MB _CUR_MAX while cLen gt 0 tStr chen numChars t cLen mbtowc wchar_t NULL tStr MB _CUR_MAX if cLen 1 numChars cLen invalid MB character Wide Characters A wide character WC or wehar is a data object of type wehar_t which is guaranteed to be able to hold the system s largest numerical code for a character wchar_t is defined in stdlib h Under IRIX 4 0 x sizeof wchar_t was 1 In IRIX 5 1 and above it is 4 All wchars on a system are the same size independent of locale encoding or any other factors Uses for wchar Strings The single advantage of WC strings is that all characters are the same size Thus a strin
223. ed_get_priority_min functions return the highest and lowest priority numbers for a given policy There are at least 32 priority values and the lowest is greater than or equal to 0 A thread can set another s priority and scheduling policy using pthread_setschedparam A simple function to set a specified priority on the current thread is shown in Example 13 2 Example 13 2 Function to Set Own Priority include lt sched h gt struct sched_param void setMyPriority int newP pthread_t myTid pthread_self int policy struct sched_param sp void pthread_getschedparam myTID amp policy amp sp sp sched_priority newP void pthread_setschedparam myTID policy amp sp Synchronizing Pthreads 288 Threads using a common address space must cooperate and coordinate their use of shared variables IRIX provides many mechanisms for coordinating threads including e POSIX semaphores for general coordination and resource management see POSIX Facilities for Mutual Exclusion on page 82 e POSIX or SVR4 message queues see Chapter 6 Message Queues e POSIX mutex objects which allow threads to gain exclusive use of a shared variable see Mutexes on page 289 e POSIX condition variables which allow a thread to wait when a controlling predicate is false see Condition Variables on page 292 Synchronizing Pthreads e POSIX read write locks which allow one thread exclusive a
224. ee fonts U Uganda country code 418 uscas 93 uscas32 93 Utopia fonts 329 V validity fault 10 video on demand VOD See guaranteed rate I O video on demand video resolution 312 virtual address space See address space virtual memory font loading 330 loading pages 9 synchronizing backing store 28 See also memory virtual page number 5 virtual size 6 virtual swap 7 9 SIGKILL from 8 See also address space VME PIO 20 VPN See virtual page number 429 Index Ww wait 265 wait timed 127 warning messages Ip log file 330 wide characters See internationalization wide characters write 196 direct 231 synchronous 229 with guaranteed rate I O 238 240 X xfd command 316 XFilterEvent 404 XFontSetExtents 388 XLFD font names See internationalization X Window System fontsets Xlib changes 384 XmbLookupString 405 xpdf command 325 328 XSetLocaleModifiers 396 XweLookupString 405 X Window System fonts See fonts installing fonts See fonts installing internationalization changes 383 limitations 383 430 Y yielding 127 You 8 Z Zambia country code 418
225. eed e acombination of the above Look now at the example of inserting an entry into a doubly linked list All the following examples assume that a record is declared as follows struct record data portion of record long prev index to previous record in the list long next index to next record in the list For the example assume that the record after which the new record is to be inserted has a read lock on it already The lock on this record must be promoted to a write lock so that the record may be edited Example 7 5 shows a function that can be used for this Example 7 5 Record Locking With Promotion Using fentl This function is called with a file descriptor and the offsets to three records in it this here and next The caller is assumed to hold read locks on both here and next This function promotes these locks to write locks If write locks on here and next are obtained Set a write lock on this Return index to this record If any write lock is not obtained Restore read locks on here and next Remove all other locks Using Record Locking Return 1 long set3Locks int fd long this long here long next struct flock lck lck l_type F_WRLCK setting a write lock lck l_whence 0 offsets are absolute lck l_len sizeof struct record Promote the lock on here to write lock lck l_start here if fcentl fd F_SETLKW
226. else IRIX Shared Memory Arenas uscasinfo either did not find a current value of 0 indicates a race with another process executing this code or it failed for some other reason In any case release allocated stuff and repeat the loop ret 0 usfreelock stuff gt updatelock arena usfree stuff arena usgetinfo returned 0 while uscasinfo swap fails arena gt initialized arena updateLock not held return arena Example 3 3 assumes that everything allocated in the arena is accessed through a collection of pointers arenaStuff The two problems to be solved are these e Which asynchronous process is the first to call usinit and therefore should allocate arenaStuff and initialize it with pointers to other objects e How can the second and subsequent processes know when the initialization of arenaStuff is complete it might take some time and the arena is completely ready for use The solution in Example 3 3 is based on the discussion in the uscasinfo 3P reference page Each process calls function joinArena If a call to usgetinfo returns nonzero it is the address of an arenaStuff_t that has been allocated by some other process Possibly that process is concurrently executing initializing the arena The current process waits until the lock in the arenaStuff_t is released On return from the ussetlock call the process has exclusive use of arenaStuff until it releases
227. ely after the timer interrupt without waiting for the end of a fixed time slice When the receiving process or thread is running or ready to run the latency is fairly short and consistent from one signal to the next Even so it is not advisable to use a repeating itimer as the time base for a real time program Under less favorable conditions signal latency can be variable and sometimes lengthy tens of milliseconds relative to a fast timer frequency Timer Facilities How Timers Are Managed The IRIX kernel can be asked to implement itimers for many processes at once each interval having a different length and starting at a different time The kernel s method differs depending on the hardware architecture this issue is discussed at length in the timers 5 reference page e Some obsolete Silicon Graphics systems have no hardware support for interval timers so the kernel had to rely on frequent periodic interrupts as a time base In those systems the precision of timer interrupts was controlled by a kernel tuning variable fasthz which determined the rate at which the kernel was interrupted to poll for an expired timer e Inall current architectures each CPU has a clock comparator that the kernel can program to cause an interrupt after a specific interval has elapsed In these systems timer interrupts have sub microsecond precision and do not impose overhead for timer polling interrupts In earlier versions of IRIX in or
228. ena at the same virtual base address This process need not be related in any way to the process that created the arena 63 Chapter 3 Sharing Memory Between Processes 64 Restricting Access to an Arena You can restrict arena access to a single process and the children it creates with sproc a share group see Process Creation and Share Groups on page 262 by calling usconfig to set CONF_ARENATYPE to US_SHAREDONLY before creating the arena When this is done the file is unlinked immediately after the arena is created Then a call to usinit with the same pathname from a different process creates a different arena one that is not shared with the first one This has several side effects that are detailed in usconfig 3 Arena Access From Processes in a Share Group An arena is a segment in the address space of a process When that process creates a new process using sproc the child process usually shares the same address space see the sproc 2 reference page and Chapter 12 Process Level Parallelism The child process has access to the arena segment on the same basis as the parent process However the child process needs to join the arena formally The child process should join the arena by calling usadd passing the address of the arena The child should test the return code of this function since it can reflect an error in either of two cases e The arena has not been created or an incorrect arena address w
229. enter the commands typelxfonts xset fp rehash This re creates symbolic links in the directory usr lib X11 fonts Type1 that point to outline font files in the directory usr lib DPS outline base and instructs the X Window System to check which fonts are available To check whether the outline fonts you added are known to the X Window System enter xlsfonts grep family name In order for the new fonts to be recognized by Ghostscript and thus be available to the gsview tool you must add the new fonts to the end of the Fontmap GS file Since later entries in Fontmap GS override earlier entries a font you add at the end supersedes any corresponding fonts supplied with Ghostscript and defined earlier in the file 327 Chapter 15 Working With Fonts 328 The format for entries in Fontmap GS is documented in the Fontmap GS file itself When you install Ghostscript on your system this file is available in the following location usr share ghostscript ghostscript_revision lib Fontmap Gs ghostscript_revision is the version of Ghostscript installed on the system In order for the new fonts to be available to the xpdf tool you must add the fonts to the usr etc xpdfrc file For information on this file see the xpdfrc 5 man page The entries for the outline fonts you added should appear on the list of font names and aliases produced by xlsfonts Adding a Font Metric File Adobe Font Metric AFM files are primarily used by
230. es and Keysyms 393 Composed Characters 393 Supported Keyboards 394 Input Methods IMs 395 Opening an Input Method 395 IM Styles 397 Root Window 397 Off the Spot 398 Over the Spot 398 On the Spot 399 Setting IM Styles 399 Using Styles 399 Input Contexts ICs 400 Find an IM Style 400 IC Values 401 Pre Edit and Status Attributes 402 Creating an Input Context 403 Using the IC 403 Events Under IM Control 404 Using XFilterEvent 404 Using XLookupString XwcLookupString and XmbLookupString 405 xxii Contents GUI Concerns 407 X Resources for Strings 407 Layout 408 Dynamic Layout 408 Constant Layout 408 Localized Layout 409 IRIS IM Localization With editres 409 Icons 409 Popular Encodings 409 The ISO 8859 Family 410 Asian Languages 411 Some Standards 412 EUC 412 Unicode 413 ISO 3166 Country Names and Abbreviations 415 Index 419 xxiii List of Examples Example 1 1 Example 1 2 Example 3 1 Example 3 2 Example 3 3 Example 3 4 Example 3 5 Example 3 6 Example 4 1 Example 4 2 Example 4 3 Example 4 4 Example 4 5 Example 4 6 Example 5 1 Example 6 1 Example 6 2 Example 6 3 Example 6 4 Example 6 5 Example 6 6 Example 6 7 Example 6 8 Example 7 1 Example 7 2 Example 7 3 Example 7 4 Using systune to Check Address Space Limits 7 Function to Lock Maximum Stack Size 25 POSIX Program to Demonstrate shm_open 58 Initializing a Shared Memory Arena 63 Setting Up an Arena With uscasinfo 67
231. es stored by a 64 bit program can t be used by a 32 bit program and vice versa Also the two programs will disagree about the size and offset of structure fields when structures contain addresses For example if you initialize an allocation arena with acreate from a 64 bit program a 32 bit program calling amalloc on that same arena will almost certainly crash or corrupt the arena pointers You can use POSIX shared memory SVR4 shared memory or basic mmap to share a segment between a 32 bit and a 64 bit program provided you take pains to ensure that both programs view the data contents as having the same binary structure and that no addresses are shared You cannot use an IRIX shared memory arena between 32 bit and 64 bit programs at all because the usinit function stores addresses in the arena POSIX Shared Memory Operations POSIX Shared Memory Operations Shared memory support specified by POSIX is based on the functions summarized in Table 3 1 Table 3 1 POSIX Shared Memory Functions Function Name Purpose and Operation mmap 2 Map a file or shared memory object into the address space shm_open 2 Create or gain access to a shared memory object shm_unlink 2 Destroy a shared memory object when no references to it remain open The use of mmap is described at length under Mapping Segments of Memory on page 12 In essence mmap takes a file descriptor and makes the contents of the described object access
232. escriptor in it specifies which file is to be synchronized The fsync operation is done following all other asynchronous operations that are pending when aio_fsync is called The synchronize operation can take considerable time depending on how much output data has been buffered Its completion is reported in the same ways as completion of a read or write see the next topic 201 Chapter 8 Using Asynchronous I O 202 Checking the Progress of Asynchronous Requests You can test the progress and completion of an asynchronous operation by polling or your program can be informed of the completion of an operation in a variety of ways In the aiocb the program can specify one of three things to be done when the operation is complete e Nothing take no action e Send a signal of a specified number e Invoke a callback function directly from the asynchronous process In addition the aio_suspend function blocks its caller until one of a list of pending operations is complete Polling for Status You can check the progress of any asynchronous operation including aio_fsync by calling aio_error passing the aiocb for that operation While the operation is incomplete aio_error returns EIINPROGRESS When the operation is complete you can check the final return code from read write or fsync using aio_return see the aio_error 3 and aio_return 3 reference pages To see in an example of polling for status see f
233. ess space or of physical memory e a portion of VME A24 or A32 bus address space when a VME bus exists on the system A mapped segment can be private to one address space or it can be shared between address spaces When shared it can be e read only to all processes e read write to the creating process and read only to others e read write to all sharing processes e copy on write so that any sharing process that modifies a page is given its own unique copy of that page Note Some of the memory mapping capabilities described in this section are unique to IRIX and nonportable Some of the capabilities are compatible with System V Release 4 SVR4 IRIX also supports the POSIX 1003 1b shared memory functions Compatibility issues with SVR4 and POSIX are noted in the text of this section Segment Mapping Function mmap The mmap function see the mmap 2 reference page creates shared or unshared segments of memory The syntax and most basic features of mmap are compatible with SVR4 and with POSIX 1003 1b A few features of mmap are unique to IRIX The mmap function performs many kinds of mappings based on six parameters The function prototype is void mmap void addr size_t len int prot int flags int fd off_t off 12 Mapping Segments of Memory The function returns the base address of a new segment or else 1 to indicate that no segment was created The size of the new segment is len rounded up to a page An a
234. essage facility offers the ability to receive an asynchronous notification in the event that a message is posted to an empty queue and no process or thread is suspended waiting for that message You do this by calling mq_notify passing a queue and a sigevent_t structure The sigevent_t is declared in sys signal h which is included by mqueue h The sigevent_t structure allows you to specify either a signal or a callback function However only the signal notification SIGEV_SIGNAL request is supported by the POSIX message queue implementation Example Programs The following programs demonstrate the use of POSIX message queues e Example 6 1 on page 146 demonstrates the use of mq_getattr to query the attributes of a queue e Example 6 2 on page 148 demonstrates the use of mq_open to create or access a message queue e Example 6 3 on page 150 demonstrates the use of mq_send to put messages onto a message queue e Example 6 4 on page 153 demonstrates the use of mq_receive to take messages from a message queue The four example programs have a consistent design and use consistent command line arguments Each accepts optional arguments that allow you to exercise most features of each function including most error return codes The following is a simple example of use First a queue is created mq_open p 0664 b 128 m 32 c x var tmp Q32x128 flags 0x0 maxmsg 32 msgsize 128 curmsgs 0 POSIX Message Queues A
235. et if given gid gopt 0 gid to set if given val vopt 0 setall value if given ct semid_ds ds IRIX Facilities for Mutual Exclusion union semun arg4 way to pass semctl 4th arg properly aligned LAC G7 while 1 c getopt arge argv k i p u g switch c case k key key key_t strtoul optarg NULL 0 break case i semid semid int strtoul optarg NULL 0 break case p permissions perms int strtoul optarg NULL 0 popt 1 break case tu uid uid int strtoul optarg NULL 0 uopt 1 break case g i gid gid int strtoul optarg NULL 0 gopt 1 break default unknown or missing argument return 1 if 1 semid i not given must have k semid semget key 0 0 if 1 semid arg4 buf amp ds if 0 semctl semid 0 IPC_STAT arg4 if popt uopt gopt if popt ds sem_perm mode perms if uopt ds sem_perm uid uid if gopt ds sem_perm gid gid if 0 semctl semid 0 IPC_SET arg4 semctl semid 0 IPC_STAT arg4 refresh info else perror semctl IPC_SET 105 Chapter 4 Mutual Exclusion printf owner uid gid d d creator uid gid d d mode 0 o nsems d n ds sem_perm uid ds sem_perm gid ds sem_perm cuid ds sem_perm cgid ds sem_perm mode ds sem_nsems else else pe
236. et to SIGEV_SIGNAL aio_sigevent sigev_signo The number of the signal This should be one of the POSIX real time signal numbers see Signal Numbers on page 114 aio_sigevent sigev_value A value to be passed to the signal handler This can be used to inform the signal handler of which I O operation has completed for example it could be the address of the aiocb 203 Chapter 8 Using Asynchronous I O 204 When you set up a signal handler for asynchronous completion do so using sigaction and specify the SA_SIGINFO flag see the sigaction 2 reference page This has two benefits any new completion signal that arrives while the first is being handled is queued and the aio_sigev sigev_value word is passed to the handler in a siginfo structure Establishing a Callback Function You request a callback at the end of an asynchronous operation by setting the following values in the aiocb aio_sigevent sigev_notify Set to SIGEV_CALLBACK aio_sigevent sigev_func The address of the callback function Its prototype must be void functionName union sigval aio_sigevent sigev_value A word to be passed to the callback function This can be used to inform the function of which I O operation has completed for example it could be the address of the aiocb The callback function is invoked from the asynchronous I O thread when the read write or fsync operation finishes This notification method has the lowest overhead and s
237. etch a fresh copy Cache Coherency in CHALLENGE Systems The CHALLENGE and Onyx systems are designed around a central bus over which all memory requests pass Each CPU board in a CHALLENGE system monitors the bus When a board observes a write to memory it checks its own cache and if it has a copy of that same line it invalidates the copy This design often called a snoopy cache because each CPU reads its neighbors mail works well when all memory access moves on a single bus Cache Coherency in Origin Systems The cache coherency design of the Origin systems is fundamentally different because in the Origin machines there is no central bus Memory access packets can flow within a node or between any two nodes Instead cache coherence is implemented using what is called a directory based scheme The following is a simplified account of it Each 128 byte line of main memory is supplied with extra bits one for each possible node plus an 8 bit integer for the number of the node that owns the line exclusively These extra bits are called directory bits The directory bits are managed as part of memory by the hub chip in the node that contains the memory The directory bits are not accessible to user level software The kernel can read and write the directory bits using privileged instructions When a CPU accesses an unmodified cache line for reading the request is routed to the node that contains the memory The hub chip in that n
238. ether the fonts you added are known to the X Window System enter xlsfonts gt tmp fontlist The names of the fonts you added should appear on the list of font names and aliases produced by xlsfonts In order for the new fonts to be recognized by Ghostscript and thus be available to the gsview tool you must add the new fonts to the end of the Fontmap GS file Since later entries in Fontmap GS override earlier entries a font you add at the end supersedes any corresponding fonts supplied with Ghostscript and defined earlier in the file The format for entries in Fontmap GS is documented in the Fontmap GS file itself When you install Ghostscript on your system this file is available in the following location usr share ghostscript ghostscript_revision 1lib Fontmap Gs ghostscript_revision is the version of Ghostscript installed on the system In order for the new fonts to be available to the xpdf tool you must add the fonts to the usr etc xpdfrc file For information on this file see the xpdfrc 5 man page Bitmap fonts should now be added to the X Window System and the IRIS GL Font Manager Since DPS needs both outline and bitmap fonts for each supported typeface it first checks which outline fonts are stored in the directory usr lib DPS outline base Then it looks for the corresponding bitmap fonts in other X font directories It ignores all other bitmap fonts Therefore DPS ignores the bitmap fonts you added until you add the corre
239. etric Files explains how to install and add font files and font metric files for system wide use e Downloading a Type 1 Font to a PostScript Printer explains how to download a Type 1 font to a PostScript printer 309 Chapter 15 Working With Fonts Font Basics 310 Fonts are collections of characters A font contains the information about the shape size and position of each character in a character set That information is needed by programs that process characters such as editing word processing desktop publishing multimedia titling and prepress application programs Almost all software components in a computer system use fonts to display messages prompts titles and so forth Binary digits are used to represent all types of information stored in a digital computer including fonts Digital typography deals with the style arrangement and appearance of typeset matter in digital systems If you want to use font and font metric files to correctly typeset text on a digital computer you need to know some basics about digital typography This section contains a brief introduction to fonts and digital typography You may want to read a book on typography for more in depth information This section covers the following topics e Terminology introduces a few basic terms e How Resolution Affects Font Size describes horizontal and vertical resolution pixels and bitmap fonts e Font Names explains
240. eues 156 Accessing an Existing Queue When the program expects the queue to exist it calls msgget passing the expected key value and omitting the IPC_CREAT flag If the queue does not exist or if the effective user and group ID of the process are not allowed access to the queue an error is returned The program receives read only or read write access depending on the access permissions of the queue just as with a file Modifying a Message Queue You can use msgctl to modify four attributes of a queue after creating or accessing it e the user ID and group ID that owns the queue e the access permissions e the limit on the total size of all queued messages The size limit on a new queue is set to the system limit 32 768 bytes as of IRIX 6 2 This determines how many messages can be waiting unreceived on the queue That in turn determines how far the message sending process can get ahead of the message reading process You can lower the limit to limit the sending process or thread more closely to the speed of the receiving process or thread Removing a Message Queue You can remove a message queue using the ipcrm command see the ipcrm 1 reference page or by calling msgctl and passing the IPC_RMID command code In many cases a message queue is meant for use within the scope of one program only and you do not want the queue to persist after the termination of that program Call msgctl to remove the queue as part of term
241. example CMD OPEN xconfirm t Tape tool not available can be internationalized to CMD OPEN xconfirm t gettxt mycatalog 376 Tape tool not available Strings and Message Catalogs In this example gettxt is invoked to access line 376 from the catalog mycatalog and the string returned by gettxt is passed to xconfirm for display If line 376 from mycatalog is not accessible then gettxt returns the string Tape tool not available For more information about FTRs see the IRIX Interactive Desktop Integration Guide Variably Ordered Referencing of printf Arguments printf and its variants can now refer to arguments in any specified order Consider the following scenario an application has chosen house from a list of objects and white from a list of colors The application wishes to display this choice The code might look like this char obj color make choices printf s s n color obj The printf call produces this white house Even once we make sure that obj and color are localized strings we are not quite finished If our locale is Spanish the printf yields blanca casa That is incorrect grammar in Spanish it should be casa blanca The solution to this problem is variably ordered referencing of printf arguments The syntax of printf format strings has been expanded to deal with this The original definition of printf is that each conversion specific
242. example programs First a semaphore set is created by semget and its existence verified with ipcs ipes s IPC status from dev kmem as of Wed Jun 19 11 19 37 1996 T ID KEY MODE OWNER GROUP Semaphores semget k Oxfab c x p 0666 s 4 semid 130 owner uid gid 1110 20 creator uid gid 1110 20 mode 0100666 nsems 4 ipcs s IPC status from dev kmem as of Wed Jun 19 11 19 59 1996 A ID KEY MODE OWNER GROUP Semaphores S 130 0x00000fab ra ra ra cortesi user The effect of the IPC_EXCL flag is tested semget k Oxfab c x semget File exists 110 IRIX Facilities for Mutual Exclusion The permissions are changed using semmod semmod i 130 p 0640 owner uid gid 1110 20 creator uid gid 1110 20 mode 0100640 nsems 4 ipcs s IPC status from dev kmem as of Wed Jun 19 11 20 09 1996 T ID KEY MODE OWNER GROUP Semaphores S 130 0x00000fab ra r cortesi user The present state of the four semaphores in the set is displayed then semop is used to increment the first two semsnap i 130 vals 0 0 0 0 nent O 0 0 zcnt 0 0 0 0 semop i 130 v semsnap i 130 vals 1 1 0 0 ments 20 lt 0 0 0 zent O 0O 0 O 0 v 1 One instance of semop is started in the background to wait on a sequence of operations The semsnap display verifies that one process is waiting on zero in semaphore 0 semop i 130 z 0 p 1 p 2 amp 9956 semsnap i 130
243. f msqid 0x 04x msqid if 1 msgctl msqid IPC_STAT amp buf printf owner d d perms 040 max bytes d n buf msg_perm uid buf msg_perm gid buf msg_perm mode buf msg_qbytes printf d msgs d bytes on queue n buf msg_qnum buf msg_cbytes else perror nmsgctl else perror msgget 162 System V Message Queues Example of msgctl The program msgctl in Example 6 6 allows you to display the state of a queue or to change the permissions owner ID group ID or maximum size of a queue The following command line arguments are supported k key Numeric identifier of a message queue for example k 99 iid Message queue ID alternative to specifying the key for example i 80 pperms Access permissions to set for example p 0664 b bytes Maximum size of the message queue for example b 0x1000 u uid Numeric user ID to set as owner g gid Numeric group ID to set as owner 163 Chapter 6 Message Queues 164 Example 6 6 Program to Demonstrate msgctl Program to test msgct1 2 msgctl k lt key gt i lt id gt b lt bytes gt p lt perms gt u lt uid gt g lt gid gt k lt key gt the key to use or i lt id gt the mq id b lt bytes gt new max number of bytes to set in msg_qbytes p lt perms gt new permissions to assign in msg_perm mode u lt uid gt new user id numeric for msg_perm ui
244. f customs in other words in a nationalized program the locale is built into the application Even if the application doesn t use ASCII or English as long as it is a single language program it is nationalized not internationalized Most older UNIX programs can be thought of as being nationalized for the United States Consider two applications hello and bonjour The application hello always produces the output Hello world and bonjour always produces Bonjour tout le monde Neither hello nor bonjour are internationalized they are both nationalized There are no special requirements for writing or porting nationalized applications whether they are text or graphics programs Terminal based programs work on suitable terminals including internationalized terminal emulators Suitable means that the terminal supports any necessary fonts and understands the encoding of the application output Graphics programs simply do as they have always done Applications using existing interfaces to operate in non English or non ASCII environments should continue to compile and run under an internationalized operating system Multilingual Software A multilingual program is one that uses several different locales at the same time Examples are described in Multilingual Support on page 345 Areas of Concern in Internationalizing Software Few developers will have to pay attention to more than a few items described in this section Most
245. f no errors so far use aio_fsync to ensure that output is complete This requires waiting yet again xi if ret if ret aio_fsync O_SYNC pab ret inWait3 pch Flag any errors for the parent proc If none count elapsed time if ret terrors lse pch gt etime clock pch gt etime if DO_SPROCS ay Rendezvous with the rest of the family then quit barrier convene nprocs endi end inProc3 228 Chapter 9 Using Synchronous High Performance File I O This chapter describes three special modes of disk I O e Using Synchronous Output on page 229 describes the effect of the O_SYNC file option e Using Direct I O on page 231 compares the use of direct to disk output with normal buffered output e Using Guaranteed Rate I O on page 236 describes a special mode of I O used with real time XFS volumes Output You use synchronous disk output to prevent the IRIX kernel scheme from deferring disk output About Buffered Output When you open a disk file and do not specify the O_SYNC flag see the open 2 reference page a call to write for that file descriptor returns as soon as the data has been copied to a buffer in the kernel address space The actual disk write may not take place until considerable time has passed A common pool of disk buffers is used for all disk files The size of the pool is set by the nbuf system confi
246. f potential numbers usually only a small fraction of the addresses are valid A segment of the address space is any range of contiguous addresses Certain segments are created or reserved for certain uses The address space is called virtual because the address numbers are not directly related to physical RAM addresses where the data resides The mapping from a virtual address to the corresponding real memory location is kept in a table created by the IRIX kernel and used by the MIPS processor chip Address Space Boundaries A process has at least three segments of usable addresses e A text segment contains the executable image of the program Another text segment is created for each dynamic shared object DSO with which a process is linked Text segments are always read only e A data segment contains the heap of dynamically allocated data space A process can create additional data segments in various ways described later e A stack segment contains the function call stack This segment is extended automatically as needed Although the address space begins at location 0 by convention the lowest segment is allocated at 0x0040 0000 4 MB Addresses less than this are intentionally left undefined so that any attempt to use them for example through an uninitialized pointer variable causes a hardware exception and stops the program Typically text segments are at smaller virtual addresses and stack and data segments at
247. fails to claim a lock before updating memory the program can seem to run correctly for hours or months before it suffers precisely the right combination of coincidences that cause two processes to update the variable at the same time 79 Chapter 4 Mutual Exclusion 80 Semaphores A semaphore is an integer count that is accessed atomically using two operations that are conventionally called P and V e The P operation mnemonic deplete decrements the count If the result is not negative the operation succeeds and returns If the result is negative the P operation suspends the calling process until the count has been made nonnegative by another process doing a V operation e The V operation mnemonic revive increments the count If this changes the value from negative to nonnegative one process that is waiting in a P operation is unblocked You can use a semaphore in place of a lock to enforce serial use of resource You initialize the semaphore to a value of 1 The P operation claims the semaphore leaving it at 0 so that the next process to do P will be suspended The V operation releases the semaphore You can also use a semaphore to control access to a pool that contains a countable number for resources For example say that a buffer pool contains n buffers A process can proceed if there is at least 1 buffer available in the pool but if there are no buffers the process should sleep until at least 1 buffer is returned
248. flag to create the queue if it doesn t exist Use the O_EXCL flag to require that the queue not exist 147 Chapter 6 Message Queues 148 Example 6 2 Program to Demonstrate mq_open Program to test mq_open 3 mq_open p lt perms gt b lt bytes gt m lt msgs gt c x lt path gt p lt perms gt access mode to use when creating default 0600 b lt bytes gt maximum message size to set default MQ_DEF_MSGSIZE m lt msgs gt maximum messages on the queue default MQ_DEF_MAXMSG f lt flags gt flags to use with mq_open including Cc use O_CREAT x use O_EXCL lt path gt the pathname of the queue required Numeric arguments can be given in any form supported by strtoul 3 ny include lt mqueue h gt define MQ_DEF_MSGSIZE lt unistd h gt lt errno h gt include lt fcntl h gt include lt stdio h gt int main int argc include include 1 define MQ_DEF_MAXMSG 16 message queue stuff 024 for getopt errno and perror O_flags char argv int perms 0600 permissions int oflags O_RDWR flags O_CREAT O_EXCL int rd 0 wr 0 r and w options mqd_t mad returned msg queue descriptor int c char path gt first non option argument struct mq_attr buf buffer for stat info buf mq_msgsize MQ_DEF_MSGSIZE buf mq_maxmsg MQ_DEF_MAXMSG whil i
249. for the unpredictable times that I O can require One obvious solution can be summarized as call read or write from a different process and run that process in a different CPU This is the essence of asynchronous I O You could implement an asynchronous I O scheme of your own design and you may wish to do so in order to integrate the I O closely with your own design of processes and data structures However a standard solution is available About Synchronous and Asynchronous I O IRIX supports asynchronous I O library calls conforming to POSIX document 1003 1b 1993 You use relatively simple calls to initiate input or output The library package handles the details of e Creating asynchronous processes or threads to perform the I O e Allocating a shared memory arena and the locks semaphores and other structures used to coordinate the I O processes or threads e Queueing multiple input or output requests to each of multiple file descriptors e Reporting results back to your program either on request through signals or through callback functions Asynchronous I O Functions Once you have opened the files and initialized asynchronous I O you perform asynchronous I O by calling some of these functions aio_read 3 Initiates asynchronous input from a file or device aio_write 3 Initiates asynchronous output to a file or device lio_listio 3 Initiates a list of operations to one or more files or devices aio_error 3 Ret
250. formation in a client window in an Off the Spot style it needs to know where the area is what color and font to render text in and so on The application gives this data to the IC for use by the IM As with the IC Values section full details are available in X Window System Third Edition XNArea XNAreaNeeded XNBackgroundPixmap XNColormap XNCursor XNFontSet XNForeground XNBackground XNLineSpacing XNSpotLocation XNStdColormap A rectangle to be used as a status or pre edit area The rectangle desired by the attribute writer Either the application or the IM may provide this information depending on circumstances A pixmap to be used for the background of windows the IM creates The colormap to use The cursor to use The fontset to use for rendering text The colors to use for rendering The line spacing to be used in the pre edit window if more than one line is used Specifies where the next insertion point is for use by XIMPreeditPosition styles Specifies that the IM should use XGetRGBColormaps with the supplied property passed as an Atom in order to find out which colormap to use Translating User Input Creating an Input Context Creating an input context is a simple matter of calling XCreateIC with a variable length list of parameters specifying IC values Example 16 10 shows a simple example that works for the root window Example 16 10 Creating an Input Context With XCreateIC
251. g and XwcDrawString render a string using a fontset These routines render in foreground only and use the raster operation from the current graphics context e XmbDrawImageString and XwcDrawImageString also render a string using a fontset These routines fill the background rectangle of the entire string with the background then render the string in the foreground color ignoring the currently active raster operation Consult the appropriate reference pages for more details on these routines New Text Extents Functions X11R6 provides MB and WC versions of width and extents interrogation routines supplying the maximum amount of space required to draw any character in a given fontset These routines depend on fontsets to interpret strings and use locale specific data The XFontSetExtents structure contains the two kinds of extents a string can have typedef struct XRectangle max_ink_extent XRectangle max_logical_extent XFontSetExtents Internationalization Support in X11R6 max_ink_extent gives the maximum boundaries needed to render the drawable characters of a fontset It considers only the parts of glyphs that would be drawn and gives distances relative to a constant origin max_logical_extent gives the maximum extent of the occupied space of drawable characters of a fontset The occupied space of a character is a rectangle specifying the minimum distance from other graphical features other graphics generated by a
252. g can be treated as an array and a program can simply index into the array in order to modify its contents Most applications char manipulation routines work with little modification other than a type change to wchar_t with appropriate attention to byte count and sizeof So when applications have significant string editing to perform they typically keep the strings in WC format while doing that editing Those WC strings may or may not be converted to or from MB strings at other points in the application Wide characters are often large and are not as space efficient as multibyte strings Applications that do not need to perform string editing probably shouldn t use wehars If an application intends to both maintain and edit large numbers of strings then the developer needs to make size and complexity trade off decisions Cultural Items Cultural Items Support Routines for Wide Characters Analogs to the routines defined in string h and stdio h are supplied in libw a and defined in widec h This includes routines such as getwchar putwchar putws wscpy wslen and wsrchr see the westring 3 reference page Conversion to MB Characters Wide characters and strings are convertible to MB strings via wctomb and westombs respectively Reading Input Data Input can be divided into two categories user events and other data This section deals with nonuser originated data which is assumed to come from file desc
253. g compiler directives The C compiler supports pragma statements for the same purpose e Take advantage of IRIX memory allocation rules to ensure that memory is allocated next to the threads that use it e Enable dynamic page migration to handle slowly changing access patterns e Use the dprof tool to learn the memory use patterns of a program see the dprof 1 reference page e Use the dplace tool to set the initial memory layout of any program without needing to modify the source code see the dplace 1 reference page e Code dynamic calls to dplace within the program to request dynamic relocation of data between one program phase and the next Using Compiler Directives for Memory Placement The Silicon Graphics Fortran 77 and Fortran 90 compilers support compiler directives for data placement You use compiler directives to specify parallel processing over loops You can supplement these with directives specifying how array sections should be distributed among the nodes that execute the parallel threads 39 Chapter 1 Process Address Space 40 You use the Fortran directives to declare a static placement for array sections You can also use directives to specify redistribution of data at runtime when access patterns change in the course of the program For details on these directives see the Fortran programmer s guides cited under Other Useful References on page xxxiv The Silicon Graphics C and C compilers sup
254. g the application to the local users The application developer is responsible for providing localizers with instructions and the mechanisms necessary to produce layout data IRIS IM Localization With editres IRIX provides an interactive method of laying out widgets for IRIS IM and Xaw the Athena Widget Set a utility called editres With editres you can construct and edit resources and see how your widgets will look on the screen the program even generates a usable app defaults file for you But note that if you hard code any resources into your IRIS IM code you won t be able to edit them using this method Icons Icons attempt to be fairly generic representations of their antecedents Unfortunately it is very difficult for a designer to know what is generic or recognizable in other cultures Therefore it is important that any pictographic representations used by an application be localizable Graphic representations can be stored as strings representing X bitmaps as names of data files containing pictographs or in whatever manner the developer thinks best so long as the developer provides a way for the localizer to produce and deliver localized pictographs This section discusses three encodings that are commonly used e The ISO 8859 Family explains the ISO 8859 family of encodings e Asian Languages describes Asian language encodings e Unicode covers the ISO 10646 and Unicode 409 Chapter 16 Internationa
255. g the use of character sets and locale specific behaviors Chapter 16 Internationalizing Your Application Internationalization is the process of generalizing an application so that it can easily be customized or localized to run in more than one language environment You can provide internationalized software that will produce output in a user s native language format data such as currency values and dates according to local standards and tailor software to a specific culture This chapter describes how to create such an application It contains the following major sections Overview of Internationalization presents an introduction to internationalization and defines some common terms Using Locales explains how to set the current locale and limitations of the locale system Character Sets Codesets and Encodings describes various ways of encoding characters the traditional ASCII being just one of these Cultural Items discusses the ways in which different cultures affect the way a string can be viewed for example in outputting or collating Locale Specific Behavior covers native language support NLS and the NLS database regular expressions and cultural data Strings and Message Catalogs describes how to create and use catalogs of messages to send diagnostic information to users in various locales Internationalization Support in X11R6 describes internationalization
256. ges Using a Shared Object In order to use a shared object your program first opens it with shm_open then maps it into memory with mmap The arguments to mmap include e the file descriptor for the shared object e the size of the memory segment e access protection flags The returned value is the base address of the segment in memory You can then use it like any block of memory For example you could create an allocation arena in the segment using the acreate function see the amalloc 3 reference page For more on the use of mmap read Segment Mapping Function mmap on page 12 and Mapping a File for Shared Memory on page 19 Example Program The program in Example 3 1 allows you to experiment with shm_open and mmap from the command line The program accepts the following command line arguments path The pathname of a shared memory segment file that exists or that is to be created p perms The access permissions to apply to a newly created segment for example p 0664 s bytes The initial size at which to map the segment for example s 0x80000 C Use the O_CREAT flag with open creating the segment if it doesn t exist xX Use the O_EXCL flag with open requiring the segment to not exist t Use the O_TRUNC flag with open truncating the file to zero length 57 Chapter 3 Sharing Memory Between Processes r Use the O_RDONLY flag with open and PROT_READ with mmap If this
257. ges in physical memory for best performance 29 Chapter 1 Process Address Space 30 About Origin Hardware You need to understand the Origin hardware at a high level in order to understand memory placement Basic Building Blocks The basic building block of an Origin system is a node a single board containing e Two MIPS R10000 CPUs each with a secondary cache of 1 MB or 4 MB e Some amount of main memory from 64 MB to 4 GB e One hub custom ASIC that manages all access to memory in the node Nodes are packaged into a module A module contains e One to four node boards e One or two routers high bandwidth switches that connect nodes and modules e Crossbow I O interface chips The Crossbow chips are used to connect I O devices of all sorts SCSI PCI FDDI and other types Each Crossbow chip connects to the hub of one or two nodes so any I O card is closely connected to as many as two main memory banks and as many as four CPUs An Origin2000 or Onyx2 system can consist of a single module or multiple modules can be connected to make a larger system Modules are connected by their routers Routers in different modules are connected by special cables the CrayLink interconnection fabric Routers form a hypercube topology to minimize the number of hops from any node to any other Uniform Addressing Physical memory is distributed throughout an Origin system with some memory installed at each node However the system
258. gnals as the basis for real time scheduling Signals Under X Windows If you plan to handle signals asynchronously in a program that uses X intrinsics you must take special steps Before establishing a signal handler with the operating system you establish one or more signal callback procedures using XtAppAddSignal Then in the asynchronous signal handling function you call XtNoticeSignal This function ensures that the established signal callback will be invoked like other callback functions when it is safe to do so This process is documented in the XtAppAddSignal 3Xt reference page The only X windows function that can safely be called from a signal handler is XtNoticeSignal POSIX Signal Facility The POSIX interface to signals is the most functionally complete and robust of the three It is the recommended interface for all new programs The functions used in POSIX style signal handling are summarized in Table 5 3 Signals Table 5 3 Functions for POSIX Signal Handling Function Purpose kill 2 Send a signal to a process or process group Discards multiple signals of the same number sigqueue 3 Queue a signal to a specified process including a sigval for added pthread_killP sigprocmask 2 pthread_sigmask 3P sigaction 2 sigaltstack 2 sigpending 2 sigsetops 3 sigsuspend 2 sigwait 3 sigtimedwait 3 sigwaitinfo 3 information about the signal Queues multiple signals of the same number
259. gramming on page 385 for more information Specify a default fontset suitable for the default locale Make sure that the application accepts localized fontset specifications via resources or message catalogs or command line options See Fontsets on page 386 for more information Overview of Internationalization 16 Use X11R5 and X11R6 text rendering routines that understand multibyte and wide character strings not the X11R4 text rendering routines XDrawText XDrawString and XDrawImageString See Text Rendering Routines on page 388 for more information 17 Use X11R5 and X11R6 MB and WC versions of width and extents interrogation routines See New Text Extents Functions on page 388 for more information 18 If you are writing a toolkit text object or if you can t use a toolkit to manage event processing for you then you have to deal with input methods Follow the instructions in Translating User Input on page 391 19 Use resources to label any object that employs some sort of text label Your application s app defaults file should specify every reasonable string resource See X Resources for Strings on page 407 for more information 20 Use dynamic layout objects that calculate layout depending on the natural localized size of the objects involved Some IRIS IM widgets providing these services are XmForm XmPanedWindow and XmRowColumn See Dynamic Layout on page 408 for more infor
260. gs 372 Message catalogs are compiled databases of strings While a major role of message catalogs is to provide communications text in locale specific natural language the strings can be used for any purpose The idea is that an application uses only strings from a catalog thus allowing localizers to supply catalogs suitable for a given locale Two different and incompatible interfaces to message catalogs exist in IRIX MNLS and XPG 4 Developers working on SVR4 or other AT amp T code or related base system utilities probably use MNLS Developers working on independent projects probably use XPG 4 Neither is a solid standard but XPG 4 is closer to being a standard than MNLS Thus applications developers who have to choose between the two interfaces are encouraged to use XPG 4 to maximize their portability XPG 4 seems to be popular in Europe This section covers the following topics e XPG 4 Message Catalogs on page 372 e SVR4 MNLS Message Catalogs on page 376 e Variably Ordered Referencing of printf Arguments on page 381 XPG 4 Message Catalogs The XPG 4 message catalog interface requires that a catalog be opened before it is read and requires that catalog references specify a catalog descriptor Since catalog references include a default to be used in case of failure applications will work normally without a catalog when in the default locale This means catalog generation is exclusively the task of localizers
261. guration variable and defaults to approximately 2 5 of all physical memory Disk buffer management is integrated with the virtual memory paging mechanism A daemon executes periodically and initiates output of buffered blocks according to the age of the data and the needs of the system 229 Chapter 9 High Performance File I O 230 The default management of disk output improves performance for the system in general but has three drawbacks e All output data must be copied from the buffer in process address space to a buffer in the kernel address space For small or infrequent writes the copy time is negligible but for large quantities of data it adds up e You do not know when the written data is actually safe on disk A system crash could prevent the output of a large amount of buffered data e When the system does decide to flush output buffers to disk it can generate a large quantity of I O that monopolizes the disk channel for a long time delaying other I O operations You can force the writing of all pending output for a file by calling fsync see the fsync 2 reference page This gives you a way of creating a known checkpoint of a file However fsync blocks until all buffered writes are complete possibly a long time When using asynchronous I O you can make file synchronization asynchronous also see Assuring Data Integrity on page 201 Requesting Synchronous Output When you open a disk file specifying O
262. he MIPS instruction architecture includes two instructions designed to let programs update memory from independent processes running concurrently in a multiprocessor e The Load Linked LL instruction loads a 32 or 64 bit word from memory and also tags that cache line so that the hardware can recognize any change to memory from any CPU in a multiprocessor e The Store Conditional SC instruction stores a 32 or 64 bit word into memory provided that the destination cache line has not been modified If the cache line has been altered since the LL instruction was used SC does not update memory and sets a branch condition The combination of LL and SC can be used to guarantee that a change to a memory location is effective even when multiple concurrent CPUs are trying to update the same location You can use LL and SC only from an assembly language module However the IRIX kernel contains a family of services that are implemented using LL SC and you can call them from C or C These calls are discussed under Using Test and Set Functions on page 92 Overview of Mutual Exclusion Locks A lock is a small software object that stands for the exclusive right to use some resource The resource could be the right to execute a section of code or the right to modify a variable in memory or the right to read or write in a file or any other software operation that must by performed serially by one process at a time Before using a serial re
263. he event to string translation routines figure out what result a given set of keystrokes should produce see Using XLookupString XwcLookupString and XmbLookupString in this section Character composition from the user s aspect is discussed in the compose 5 and composetable 5 reference pages Explicit Composition Explicit composition is requested when the user presses the Compose key and then types a key sequence that corresponds to the desired character For example to compose the character fi under some keymaps you might press the Compose key and then type n Note The xmodmap 1 reference page tells how to map the XK_Multi_key keysym onto whatever key you want to use as Compose Implicit Composition Implicit composition mimics many existing European typewriters that have dead keys keys that type a character but do not advance the carriage When a special dead key is struck the system attempts to compose a character using the next character struck For example on a keyboard that had a diaeresis and an O but no O you would strike and then o to compose O Implicit composition support usually comes with some specified way to leave characters uncomposed Supported Keyboards IRIX currently supports 16 keyboard layouts American Belgian Czech Danish English French German Italian Norwegian Polish Portuguese Russian Spanish Swedish Swiss and Turkish The American keyboard needs only ASCI
264. he following ways Text Pages of program text executable code of programs and dynamically linked libraries can be retrieved on demand from the program file or library files on disk Data Pages of data from the heap and stack can be retrieved from the swap partition or file on disk Mapped When a segment is created by mmap a backing store file is specified by the program see Mapping Segments of Memory on page 12 Never used Pages that have been defined but never used can be created as pages of binary zero when they are needed Chapter 1 Process Address Space 10 When a process refers to a VPN that is defined but invalid a hardware interrupt occurs The interrupt handler in the IRIX kernel chooses a page of physical RAM to hold the page In order to acquire this space the kernel might have to invalidate some other page belonging to your process or to another process The contents of the needed page are read from the appropriate backing store into memory and the process continues to execute Page validation takes from 10 to 50 milliseconds Most applications are not impeded by page fault processing but a real time program cannot tolerate these delays The total size of all the defined pages in an address space is displayed by the ps command under the heading SZ The aggregate size of the pages that are actually in memory is the resident set size displayed by ps under the heading RSS Tip A sophisticated IRIX user
265. he handler These functions are often used in library code with the push operation done on entry to the library and the pop done upon exit from the library The push and pop operations are in fact implemented partly as macro code For this reason calls to them must be strictly balanced a pop for each push and each push pop pair must appear in a single C lexical scope A nonstructured jump such as a longjmp see the setjmp 3 reference page or goto can cause unexpected results Call pthread_atfork to register three handlers related to a UNIX fork call The first handler executes just before the fork takes place the second executes just after the fork in the parent process the third executes just after the fork in the child process The fork operation creates a new process with a copy of the calling process s address space including any locked mutexes or semaphores Typically the new process immediately calls exec to replace the address space with a new program When this is the case there is no need for pthread_atfork see the exec 2 and fork 2 reference pages However if the new process continues to execute with the inherited address space including perhaps calls to library code that uses pthreads it may be necessary for the library code to reinitialize data in the address space of the child process You can do this in the fork event handlers Terminating a Thread A thread begins execution in the function that is
266. he parallel features of the three languages from Silicon Graphics are documented in detail in the manuals listed in Table 11 1 Table 11 1 Documentation for Statement Level Parallel Products Document Manual Number Contents C Language Reference 007 0701 nnn Covers all pragmas including parallel ones Manual IRIS Power C User s Guide 007 0702 nnn Use of Power C source analyzer to place pragmas automatically MIPSpro Fortran 77 007 2361 nnn General use of Fortran 77 including parallelizing Programmer s Guide assertions and directives MIPSpro Power Fortran 77 007 2363 nnn Use of the Power Fortran source analyzer to place Programmer s Guide directives automatically MIPSpro Fortran 90 007 2761 nnn General use of Fortran 90 including parallelizing Programmer s Guide assertions and directives MIPSpro Power Fortran 90 007 2760 nnn Use of the Power Fortran 90 source analyzer to place Programmer s Guide directives automatically Products from Other Vendors In addition to these products from Silicon Graphics the High Performance Fortran HPF compiler from the Portland Group is a compiler for Fortran 90 augmented to the HPF standard It supports automatic parallelization Refer to http www pgroup com for more information Creating Parallel Programs The FORGE products from Applied Parallel Research APRI contain a Fortran 77 source analyzer that can insert parallelizing directives although not the directives supported by
267. he right place in fact the pre edit window often has no borders and is invisible to the user giving the appearance of On the Spot input The application manages the status area as in Off the Spot but specifies the location of the editing so that the IM can place pre edit data over that spot Translating User Input On the Spot On the Spot input is by far the most complex for the application developer The IM delivers all pre edit data via callbacks to the application which must perform in place editing complete with insertion and deletion and so on This approach usually involves a great deal of string and text rendering support at the input generation level above and beyond the effort required for completed input Since this may mean a lot of updating of surrounding data or other display management everything is left to the application There is little chance an IM could ever know enough about the application to be able to help it provide user feedback The IM therefore provides status and edit information via callbacks Done well this style can be the most intuitive one for a user Setting IM Styles A style describes how an IM presents its pre edit and status information to the user An IM supplies information detailing its presentation capabilities The information comes in the form of flags combined with OR The flags to use with each style are as follows Root Window XIMPreeditNothing XIMStatusNothing Off the Spot XIMPree
268. he same manner as they are set only the lock type is different F_UNLCK or F_ULOCK An unlock cannot be blocked by another process An unlock can affect only locks that were placed by the unlocking process Getting Lock Information You can determine which processes if any are blocking a lock from being set This can be used as a simple test or as a means to find locks on a file To find this information set up a lock as in the previous examples and use the F GETLK command in the fentl call If the lock passed to fentl would be blocked the first blocking lock is returned to the process through the structure passed to fentl That is the lock data passed to fentl is overwritten by blocking lock information The returned information includes two pieces of data _pidf and I_sysid that are used only with F_GETLK These fields uniquely identify the process holding the lock For systems that do not support a distributed architecture the value in _sysid can be ignored If a lock passed to fentl using the F LGETLK command is not blocked by another lock the I_type field is changed to F_UNLCK and the remaining fields in the structure are unaffected Example 7 7 shows how to use this capability to print all the records locked by other processes Note that if several read locks occur over the same record only one of these is found 187 Chapter 7 File and Record Locking Example 7 7 Detecting Contending Locks Using fcntl
269. her process unsets the lock 91 Chapter 4 Mutual Exclusion 92 Using Barriers The functions to manage and use barriers are summarized in Table 4 9 Table 4 9 IRIX IPC Functions for Barriers Function Name Purpose and Operation new_barrier 3P Allocate and initialize a barrier in a specified arena free_barrier 3P Release the storage associated with a barrier barrier 3P Wait at a barrier until a specified number of processes have gathered init_barrier 3P Reinitialize a barrier does not release any processes waiting The main process uses new_barrier to allocate a barrier in some arena To use the barrier each process calls barrier passing the number of processes that are supposed to meet before proceeding Note The barrier function assumes that it is used on a multiprocessor It always passes time by spinning in an empty loop When used on a uniprocessor or when used on a multiprocessor with fewer available CPUs than barrier processes a call to barrier n can be quite inefficient The waiting functions spin until each in turn uses up its time slice In general it is not a good idea to use barrier except in a multiprocessor with a number of CPUs approximately equal to the number of coordinating processes Using Test and Set Functions The C library includes a family of functions that apply the MIPS instructions Load Linked and Store Conditional to modify memory words in a reliable way ina multiproce
270. her chunk until none are left undone INTERLEAVE Fach process executes C iterations at C Q C 2Q C 3Q GSS Each process executes chunks of decreasing size N 2P N 4P 259 Chapter 11 Statement Level Parallelism 260 The variables used in Table 11 2 are as follows N Number of iterations in the loop determined from the source or at run time P Number of available processes set by default or by environment variable see Controlling the Degree of Parallelism on page 258 Q Number of a process from 0 to N 1 C Chunk size set by directive or by environment variable The effects of the scheduling types depend on the nature of the loops being parallelized For example e The SIMPLE method works well when N is relatively small However unless N is evenly divided by P there will be a time at the end of the loop when fewer than P processes are working and possibly only one e The DYNAMIC and INTERLEAVE methods allow you to set the chunk size to control the span of an array referenced by each process You can use this to reduce cache effects When N is very large so that not all data fits in memory INTERLEAVE may reduce the amount of paging compared to DYNAMIC e The guided self scheduling GSS method is good for triangular matrices and other algorithms where loop iterations become faster toward the end You can use source directives or pragmas within the program to specify the scheduling type and c
271. hortest latency but it requires careful design to avoid race conditions in the use of shared variables The asynchronous I O threads share the address space of the processes or threads that initialize asynchronous I O They may execute in a different CPU Since the callback function could be entered at any time it must coordinate its use of shared data structures This is a good place to use a lock see Locks on page 79 Locks have very low overhead in cases such as this where there is likely to be little contention for the use of the lock Tip You can call aio_read or aio_write from within a callback function or within a signal handler This lets you start another operation with the least delay The code in Example 8 3 demonstrates a hypothetical set of subroutines to schedule asynchronous reads and writes using a single aiocb The principle functions and global variables it uses are pendingIO An array of records each holding one request for an I O operation dontTouchThatStuff A lock used to gain exclusive use of pendingIO About Synchronous and Asynchronous I O scheduleRead yeahWeFinishedOne initiatePending A function that accepts a request to read some amount of data from a specified file descriptor at a specified file offset It places the request in pendingIO and then if no asynchronous operation is under way initiates it The callback function that is entered when an asynchronous operation comp
272. how it is created Interrogating the Memory System on page 11 summarizes the ways your program can get information about the address space Mapping Segments of Memory on page 12 documents the different ways that you can create new memory segments with predefined contents Locking and Unlocking Pages in Memory on page 23 discusses when and how to lock pages of virtual memory to avoid page faults Additional Memory Features on page 27 summarizes functions for address space management Using Origin2000 Nonuniform Memory on page 29 describes the use of CC NUMA memory in the Origin2000 and Onyx2 systems Defining the Address Space Each user level process has a virtual address space This term means simply the set of memory addresses that the process can use without error When 32 bit addressing is in use addresses can range from 0 to Ox7fffffff that is 2831 possible numbers for a total theoretical size of 2 gigabytes Numbers greater than 2431 are in the IRIX kernel s address space When 64 bit addressing is used a process s address space can encompass 240 numbers The numbers greater than 240 are reserved for kernel address spaces For more details on the structure of physical and virtual address spaces see the IRIX Device Driver Programmer s Guide and the MIPS architecture documents listed on page xxxiv Chapter 1 Process Address Space Although the address space includes a vast quantity o
273. hunk size for particular loops Where you do not specify the scheduling the run time library uses a default method and chunk size You can establish this default scheduling type and chunk size using environment variables Distributing Data In any statement level parallel program memory cache contention can harm performance This subject is covered under Dealing With Cache Contention on page 34 When a statement parallel program runs in an Origin2000 or Onyx2 system the location of the program s data can affect performance These issues are covered at length under Using Origin2000 Nonuniform Memory on page 29 Chapter 12 Process Level Parallelism The process is the traditional unit of UNIX execution The concept of the process and its relationship to the concept of a thread are covered under Process Level Parallelism on page 248 The purpose of this chapter is to review how you can use IRIX processes to perform parallel processing in a single program 261 Chapter 12 Process Level Parallelism Using Multiple Processes 262 In general you can create a new process for each unit of work that your program could do in parallel The processes can share the address space of the original program or each can have its own address space You design the processes so that they coordinate work and share data using any and all of the interprocess communication IPC features discussed in Part II Interproce
274. ible as a segment of memory in the address space In IRIX a file descriptor can describe a disk file or a device or a special pseudo device such as dev kmem Thus mmap can make a variety of objects part of the address space POSIX adds one more type of mappable object a persistent shared segment you create using the shm_open function Creating a Shared Object The shm_open function is very similar to the open function and takes the same arguments compare the shm_open 2 and open 2 reference pages The arguments are as follows path Name of object a character string in the form of a file pathname oflag Option flags detailed in the reference page and discussed in following text mode Access mode for the opened object In order to declare shm_open and its arguments you need to include both sys mman h and fcntl h header files 55 Chapter 3 Sharing Memory Between Processes 56 Shared Object Pathname The POSIX standard says that a shared object name has the form of a file pathname but the standard leaves it implementation defined whether the object is actually a file or not In the IRIX implementation a shared memory object is also a file The pathname you specify for a shared memory object is interpreted exactly like the pathname of a disk file that you pass to open When you create a new object you also create a disk file of the same name See POSIX IPC Name Space on page 48 You can display th
275. ic key and has the following attributes which are defined in the header file sys ipc h e the UID and GID of the creating process e the UID and GID of the owning process which can be different from the creator e access permissions in the same format as used with files The commands and functions used to manage the IPC name space are listed in Table 2 2 Table 2 2 SVR4 IPC Name Space Management Function Name Purpose and Operation ipcs 1 List existing shared memory segments and other IPC objects in the system name space with their status ipcrm 1 Remove a shared memory segment or other IPC object from the system name space ftok 3 Create a semi unique numeric key based on a file pathname Configuring the IPC Name Space SVR4 IPC objects are stored in kernel tables of limited fixed size You configure the size of these tables by changing kernel tunable parameters These parameters are documented in detail in the book IRIX Admin System Configuration and Operation 007 2859 nnn See Appendix A IRIX Kernel Tunable Parameters Listing and Removing Persistent Objects Objects in the IPC name space are created by programs and can be removed by programs However IPC objects by definition are used by multiple processes and it is sometimes a problem to determine which process should remove an object and when it is safe to do SO For this reason IPC objects are often created and never removed In these cases they
276. ications The old asctime and ctime functions are now obsolete use strftime instead For more information see the strftime 3C reference page Character Classification and ctype The ctype h header file is described in the ctype 3C reference page and defines macros to determine various kinds of information about a given character isalpha isupper islower isdigit isxdigit isalnum isspace ispunct isprint isgraph Q iscntrl and isascii 357 Chapter 16 Internationalizing Your Application 358 When programmers knew that a character set was ASCII some convenient assumptions could be made about characters and letters It was common for programmers to do arithmetic with the ASCII code values in order to perform some simple operations For example raising a character to upper case could be done by subtracting the difference between the code for a and the code for A Numeric characters could be identified by inspection if they fell between 0 and 9 they were numeric otherwise they weren t You could tell if a character was for instance printable a letter or asymbol by comparing to known encoding values Macros for such activity have long been available in ctype h but lots of programs did character arithmetic anyway Since character encoding and linguistic semantics are completely independent such arithmetic in an internationalized program leads to unpleasant results Furthermore characters exist o
277. icy and priority in the attribute object are ignored Scheduling scope priorities and policies are described in Scheduling Pthreads on page 286 Thread Stack Allocation Each pthread has an execution stack area in memory By default pthread_create allocates stack space from dynamic memory and automatically releases it when the thread terminates You use pthread_attr_setstacksize to specify the size of this stack area You cannot specify a stack size less than a minimum A pthread process can find the minimum by calling sysconf with SC_THREAD_STACK_MIN see the sysconf 3C reference page Threads may overrun their stack area By default a thread s stack is created with guard protection and extra memory is allocated at the overflow end of the stack as a buffer If an application overflows into this buffer an exception results a SIGSEGV signal is delivered to the thread The guardsize attribute controls the size of the guard area for the created thread s stack and protects against overflow of the stack pointer The guardsize attribute is set using pthread_attr_setguardsize Note Because thread stack space is taken from dynamic memory the allocation is charged against the process virtual memory limit not the process stack size limit as you might expect 279 Chapter 13 Thread Level Parallelism Executing and Terminating Pthreads 280 The functions for managing the progress of a thread are summarized in
278. ide characters Expression syntax is that of regexp augmented with internationalization expressions 365 Chapter 16 Internationalizing Your Application 366 Internationalized Regular Expressions A few utilities distributed with IRIX in particular grep see the grep 1 reference page support internationalized regular expressions which provide additional syntax for matching character classes sequences or ranges The internationalized regular expressions supported by the wsregexp library are as shown in Table 16 7 Table 16 7 Character Expressions in Internationalized Regular Expressions Expression Description c class The single character c where c is not a special character A character class expression Any character of type class as defined by category LC_CTYPE in the program s locale for example see isalpha For class substitute one of the following alpha a letter upper an upper case letter lower a lower case letter digit a decimal digit xdigit a hexadecimal digit alnum an alphanumeric letter or digit space a character that produces white space in displayed text punct a punctuation character print a printing character graph a character with a visible representation cntrl a control character An equivalence class Any collation element defined as having the same relative order in the current collation sequence as c As an example if A and a belong to the same e
279. iform Memory on page 29 Most programs have a single thread of execution that runs as if it were in a uniprocessor employing the facilities of a single CPU The IRIX operating system applies CPUs to different programs in order to maximize system throughput You can write a program so that it makes use of more than one CPU at a time The software interface that you use for this is the parallel programming model The IRIX operating system gives you a variety of such interfaces Each one is designed around a different set of assumptions about the hardware especially the memory system Each model is implemented using a different library of code linked with your program In some cases you can design a mixed model program but in general this is a recipe for confusion Parallel Hardware Models Parallel Programs on Uniprocessors It might seem a contradiction but it is possible to execute some parallel programs in uniprocessors Obviously you would not do this expecting the best performance However it is easier to debug a parallel program by running it in the more predictable environment of a single CPU on a multiprocessor or on a uniprocessor workstation Also you might deliberately restrict a parallel program to one CPU in order to establish a performance baseline Most parallel programming libraries adapt to the available hardware They run concurrently on multiple CPUs when the CPUs are available up to some programmer defined limi
280. igh bit of any data byte to convey special information See Eight Bit Cleanliness on page 347 for instructions If you re writing a multilingual application you must do one of two things e fork and then call setlocale differently in each process e call setlocale repeatedly as necessary to change from language to language See Multilingual Support on page 345 for more information Use wide character WC or multibyte MB characters and strings to allow for more than one byte per character this is needed for Asian languages which often require two or even four bytes per character See Character Representation on page 348 for more information 337 Chapter 16 Internationalizing Your Application 338 10 11 12 13 14 15 Do not rely on ASCII and English sorting rules Locale specific collation should be performed with strcoll and strxfm These are table driven functions the tables are supplied as part of locale support See Collating Strings on page 354 for more information Use the localeconv function to find out about general details of numeric formatting Use strfmon to format currency amounts in particular See Specifying Numbers and Money on page 355 for more information Use strftime to format dates and times strftime gives a host of options for displaying locale specific dates and times See Formatting Dates and Times on page 357 for more informa
281. ility which allows the user to block on a receive for a user specified amount of time MPI does not have a corresponding call e PVM includes a routine that allows users to define their own receive contexts to be used by subsequent PVM receive routines Communicators in MPI provide this type of functionality to a limited extent On the other hand MPI provides several features that are not available in PVM including a variety of communication modes communicators derived data types additional group management facilities and virtual process topologies as well as a larger set of collective communication calls PART FIVE Working With Fonts Chapter 15 Working With Fonts Describes the use of fonts and font metric files within the X Window System and the installation of bit mapped and Type 1 fonts Chapter 15 Working With Fonts This chapter describes how to work with fonts on Silicon Graphics computers It begins with an introduction to fonts and digital typography Then it explains which fonts are available and how to install additional fonts It also covers how to download outline fonts in the Type 1 format to a PostScript printer This chapter contains these sections e Font Basics defines fonts and provides some general background information e Using Fonts With the X Window System discusses some of the most useful font utilities of the X Window System e Installing and Adding Font and Font M
282. ime 368 localization defined 335 empty strings 342 nonempty strings 343 lock 79 IRIX 90 91 Index lockf to protect mapped file 19 lock removal order 187 log file warning messages 330 Ip log file warning messages 330 Iseek for file size 16 with asynchronous I O 198 Macau country code 417 madvise 29 malloc 6 7 use 9 used to find limit of swap 7 mandatory file locking 190 MAP_AUTOGROW flag 14 15 20 MAP_FIXED flag 17 21 22 23 MAP_LOCAL flag 15 MAP_PRIVATE flag 14 18 MAP_SHARED flag 14 18 memory 3 42 address ranges of 3 backing store for 6 interrogating size of 11 locking pages in 23 27 page 5 protection 28 segment 4 See also memory mapping virtual memory 12 memory shared See IPC memory mapping 6 12 23 and file access permissions 17 at fixed addresses 22 choosing segment address for 21 conflicts with normal file access 18 for I O 15 19 locking mapped file 26 mandatory file locks with 19 of kernel memory 20 of NFS mounted filemsync 17 of physical memory 20 of segment of zeros 19 of VME device 20 private copy of file 18 replacing a mapped segment 17 to create shared segments 19 when pages are defined 15 MENUCMD 380 message catalogs 372 382 closing 373 file typing rules 380 incompatibilities 372 locating 374 MNLS fmtmsg 379 pfmt 378 pfmt flags 378 pfmt format strings 379 strings 376 using 376
283. imit must be set higher CONF_CHMOD The effective file permissions on arena access The default is 600 allowing only processes with the effective UID of the creating process to attach the arena CONF_ARENATYPE Establish whether the arena can be attached by general processes or only by members of one program a share group CONF_LOCKTYPE Whether or not lock objects allocated in the arena collect metering statistics as they are used CONF_ATTACHADDR An explicit memory base address for the next arena to be created see Choosing a Segment Address on page 21 CONF_HISTON Start and stop collecting usage history more bulky than metering CONF_HISTOFF information for semaphores in a specified arena CONF_HISTSIZE Set the maximum size of semaphore history records See the usconfig 3 reference page for a complete list of attributes The use of metering and history information for locks and semaphores is covered in Chapter 4 Mutual Exclusion Tip In programs that use an arena and start a varying number of child processes it is a common mistake to find that the eighth child process cannot join the arena This occurs simply because usconfig has not been called with CONF_INITUSERS to set the number of users higher than the default 8 before the arena was created IRIX Shared Memory Arenas Creating an Arena After setting the arena attributes with usconfig the program calls usinit specifying a file pathname st
284. in fentl when using an _whence value of 1 Since there is no way to perform the sequence Iseek fentl as an atomic operation there is an obvious potential for race conditions a lock might be set using a file pointer that was just changed by another process 189 Chapter 7 File and Record Locking The solution is to have the child process close and reopen the file This creates a distinct file descriptor for the use of that process Another solution is to always use the fentl function for locking with an _whence value of 0 or 2 This makes the locking function independent of the file pointer processes might still contend for the use of the file pointer for other purposes such as direct access input Deadlock Handling A certain level of deadlock detection and avoidance is built into the record locking facility This deadlock handling provides the same level of protection granted by the usr group standard lockf call This deadlock detection is valid only for processes that are locking files or records on a single system Deadlocks can potentially occur only when the system is about to put a record locking system call to sleep A search is made for constraint loops of processes that would cause the system call to sleep indefinitely If such a situation is found the locking system call fails and sets errno to the deadlock error number If a process wishes to avoid using the system s deadlock detection it should set its loc
285. ination System V Message Queues Using SVR4 Message Queues The SVR4 functions for using message queues are summarized in Table 6 5 Table 6 5 SVR4 Functions for Using Message Queues Function Name Purpose and Operation msgsnd 2 Send a message to a queue msegrcv 2 Receive a message from a queue Sending a Message To send a message to a queue call msgsnd and specify the queue the address and length of the message data and a flag number that can contain IPC_NOWAIT The message buffer contains an integer specifying the type of the message Messages on the queue are retained in arrival sequence within types The message is copied out of the caller s buffer so the buffer can be reused immediately after a successful send If the queue is full the msgsnd function blocks unless the IPC_NOWAIT flag is passed Receiving a Message To receive a message call msgrcv and specify the queue the address and size of a buffer a number for the desired message type and a flag value If the queue is empty the msgrcv function blocks unless the IPC_NOWAIT flag is passed If the message buffer is not as large as the message an error is returned unless the IPC_NOERROR flag is passed Then the message is simply truncated to fit the buffer The type value can be 0 to specify any type or it can be a specific positive type number to select the first number of that type Finally it can be a negative value to spe
286. ing An advisory lock is visible only when a program explicitly tries to place a conflicting lock An advisory lock is not visible to the file I O system functions such as read and write A process that does not test for an advisory lock can violate the terms of the lock for example by writing into a locked record Advisory locks are useful when all processes make an appropriate record lock request before performing any I O operation When all processes use advisory locking access to the locked data is controlled by the advisory lock requests The success of advisory locking depends on the cooperation of all processes in enforcing the locking protocol it is not enforced by the file I O subsystem Mandatory Locking Mandatory record locking is enforced by the file I O system functions and so is effective on unrelated processes that are not part of a cooperating group Respect for locked records is enforced by the creat open read and write system calls When a record is locked access to that record by any other process is restricted according to the type of lock on the record Cooperating processes should still request an appropriate record lock before an I O operation but an additional check is made by IRIX before each I O operation to ensure the record locking protocol is being honored Mandatory locking offers security against unplanned file use by unrelated programs but it imposes additional system overhead on access to the co
287. ing multibyte characters conversions to constant size characters and the number of bytes in a character and string e Wide Characters explains wchar strings support routines and conversion to multibyte characters e Reading Input Data covers nonuser originated data For information on installing and using fonts with an application refer to Chapter 15 Working With Fonts Eight Bit Cleanliness A program is 8 bit clean if it does not use the high bit of any data byte to convey special information ASCII characters are specified by the low seven bits of a byte so some programs use the high bit of a data byte as a flag such programs are not 8 bit clean Internationalized programs must be 8 bit clean because they cannot expect data to be in the form of ASCII bytes non ASCII character sets usually use all eight bits of each byte to specify the character But a program must go out of its way to manipulate bytes based on the value of the high bit and since changing data without cause is seldom desirable most programs are already 8 bit clean The old csh before this problem was fixed in the IRIX 5 0 release was a good example of a program that was not 8 bit clean it used the high bit in input strings to distinguish aliases from unaliased commands An effect of this misuse was that csh stripped the eighth bit from all characters For example the user command echo I know an architect named Mafnosa Produced the respon
288. ing steps which are illustrated in Example 9 2 1 Open the file with the options O_CREAT O_EXCL and O_DIRECT That is the file must not exist at this point and must be opened for direct I O see Using Direct I O on page 231 2 Modify the file descriptor to set its extent size which is the minimum amount by which the file will be extended when new space is allocated to it and also to establish that the new file is a real time file This is done using fentl with the FS_FSSETXATTR command Check the value returned by fentl as several errors can be detected at this point The extent size must be chosen to match the characteristics of the disk for example it might be the stripe width of a striped disk 3 Write any amount of data to the new file Space will be allocated in the real time subvolume instead of the data subvolume because of step 2 Check the result of the first write call carefully since this is another point at which errors could be detected Once created you can read and write a real time file the same as any other file except that it must always be opened with O_DIRECT You can use a real time file with asynchronous I O provided it is created with the PROC_SHARE_GUAR option Using Guaranteed Rate I O Example 9 2 Function to Create a Real time File include lt sys fcntl h gt include lt sys fs xfs_itable h gt int createRealTimeFile char path __uint32_t esize struct fsxattr
289. ing the address of a function to be called when the signal is received The signal handling function is entered asynchronously without regard for what the process was doing at the time the signal was delivered You cannot be sure what code was executing when the signal handler is called it could have been any function in your own code or it could have been code in the C library or in any layer of the X Windows or Motif support libraries Signals All three interfaces provide for passing the signal number as the first argument of the signal handling function Other arguments to the handler function depend on the interface used and the options you specify when establishing the handler You can create an alternate memory area to be used as a stack when executing the signal handler Typically a signal handler does not require a great deal of stack space On the other hand each POSIX thread has limited stack space and when you provide an alternate signal handling stack you do not have to allow for possible signals in allocating thread stack space see Setting Signal Actions on page 285 Synchronous Signal Handling Using the POSIX signal interface you can process signals in a synchronous way as a stream of input items to your program This allows you to design your program so that signals are received when the process is in a known state without the uncertainties of asynchronous delivery Signal Latency The time that elapses fr
290. ing work areas used by subprocesses or threads in the parent process This practice ensures that all memory is allocated in the node where the parent runs Instead the parent process should allocate and touch only data space that is used by multiple threads Work areas that are unique to a thread should be allocated and touched first by that thread then they are placed in the node where the thread runs Using Origin2000 Nonuniform Memory Shared memory arenas see Chapter 3 Sharing Memory Between Processes are based on memory mapping However the library function or system call that creates an arena will typically touch at least the beginning of the arena in order to initialize it If each thread is to have a private data area within an arena make the private area at least a page in size allocated on a page size boundary and allocate it from the thread that uses it Using Round Robin Allocation When a Fortran or C program uses statement level parallelism based on the multiprocessing library libmp see Managing Statement Parallel Execution on page 258 you can replace the first touch allocation rule with round robin allocation When you set an environment variable _DSM_ROUND_ROBIN libmp distributes all data memory for the program across the nodes in which the program runs Each new virtual page is allocated in a different node Round robin allocation does not produce optimal placement because there is no relationship bet
291. ion to use the mutex Enable mutex sharing by changing the default PTHREAD_PROCESS_PRIVATE attribute to PTHREAD_PROCESS_SHARED Note The PTHREAD_PRIO_INHERIT attribute is not available with pthread_mutexattr_setpshared 291 Chapter 13 Thread Level Parallelism 292 By default no error checking is performed on threads that attempt to use a mutex For example a thread that attempts to lock a mutex that it already owns deadlocks Using pthread_mutexattr_settype with PTHREAD_MUTEX_ERRORCHECK allows you to have the lock call return an error instead If recursive mutexes are required PTHREAD_MUTEX_RECURSIVE enables recursive mutexes Using Mutexes The functions for claiming releasing and using mutexes are summarized in Table 13 8 Table 13 8 Functions for Using Mutexes Function Purpose pthread_mutex_lock 3P Claim a mutex blocking until it is available pthread_mutex_trylock 3P Test a mutex and acquire it if it is available else return an error pthread_mutex_unlock 3P Release a mutex pthread_mutex_getprioceiling 3P Query the minimum priority of a mutex pthread_mutex_setprioceiling 3P Set the minimum priority of a mutex To determine where mutexes should be used examine the memory variables and other objects such as files that can be accessed from multiple threads Create a mutex for each set of shared objects that are used together Ensure that the code acquires the proper mutex before it modifies the sh
292. ions of the Locale System This section explains multilingual support misuse of locales and the absence of filesystem information for encoding types Multilingual Support There can be only one locale at a time associated with any given process in an internationalized system Therefore although multilingual applications which give the appearance of using more than one locale at a time can be created internationalization does not provide inherent support for them Here are two examples of multilingual programs e An application creates and maintains windows on four different displays operated by four different users The program has a single controlling process which is associated with only one locale at any given time However the application can switch back and forth between locales as it switches between users so the four users may each use a different locale e Inasophisticated editing system with a complex user interface a user may wish to operate the interface in one language while entering or editing text in another For instance a user whose first language is German may wish to compose a Japanese document using Japanese input and text manipulation but with the user interface operating in German There is no standard interface for such behavior In writing a multilingual application the first task is identifying the locales for the program to run in and when they apply There is no standard method for performing this ta
293. it operation of commands that communicate with other systems cannot be guaranteed in all circumstances For example intersystem mail may be restricted to 7 bit data by the underlying network 8 bit data and filenames may not be portable to noninternationalized systems and so forth Under these circumstances it is recommended that you use only characters defined in the ASCII 7 bit range of characters for data transfer between machines and you use only characters defined in the Portable Filename Character Set for naming remote files NLS Library Functions The list below shows library functions usable by internationalized application programs atof isgraph scanf toupper catclose islower setlocale vfprintf catgets isprint sprintf vprintf catopen ispunct sscanf vsprintf fprint isspace streoll fscanf isupper strerror gcvt nl_langinfo strftime isalnum perror strtod isalpha printf strxfrm iscntrl regexp tolower Also all functions defined in the X Open Portability Guide Volume 2 XSI System Interfaces and Headers and X Open Portability Guide Volume 3 XSI Curses Interface provide 8 bit transparency on X Open compliant systems XSI Curses Interface The XSI curses interface is internationalized For more information see the X Open Portability Guide Volume 3 XSI Curses Interface 371 Chapter 16 Internationalizing Your Application Strings and Message Catalo
294. ity portability scope latency and bandwidth Compatibility Portability Scope Latency Bandwidth If you are starting with an existing program that uses one of the three models or if you want to reuse code from such a program or if you personally are highly familiar with one of the three you will likely choose that model in order to minimize development time The SHMEM library is portable among all Silicon Graphics Cray systems including both IRIX and UNICOS MK However it is not supported on systems of other types Both MPI and PVM are industry standard libraries that are widely available in public domain implementations The SHMEM library can be used only within a single multiprocessor such as Cray T3E or an Origin2000 You can use MPI or PVM to distribute a program across all nodes in an Silicon Graphics Array or across a heterogeneous network Latency the start up delay inherent in sending any one message of any size is the shortest in SHMEM MPI within a single system is a close second both use memory to memory copy MPI latency across an Array using the Silicon Graphics proprietary HIPPI Bypass is an order of magnitude greater MPI or PVM latency using ordinary HIPPI or TCP IP is greater still The rate at which the bits of a message are sent is the highest in SHMEM and MPI within a single system MPI bandwidth over a HIPPI link is next followed by PVM If you require the highest performance within a singl
295. ized If you have comments about the technical accuracy content or organization of this document please tell us Be sure to include the title and document number of the manual with your comments Online the document number is located in the frontmatter of the manual In printed manuals the document number can be found on the back cover You can contact us in any of the following ways e Send e mail to the following address techpubs sgi com e Use the Feedback option on the Technical Publications Library World Wide Web page http docs sgi com e Contact your customer service representative and ask that an incident be filed in the SGI incident tracking system e Send mail to the following address Technical Publications SGI 1500 Crittenden Lane M S 535 Mountain View California 94043 1351 We value your comments and will respond to them promptly PART ONE The Process Address Space Chapter 1 Tells how the virtual address space of a process is created under IRIX Lists the parts of the address space and their sources discusses memory mapping gives tips on cache management Chapter 1 Process Address Space When planning a complex program you must understand how IRIX creates the virtual address space of a process and how you can modify the normal behavior of the address space The major topics covered here are as follows Defining the Address Space on page 3 tells what the address space is and
296. ject gives the machine state at the time the signal was delivered The ucontext_t is detailed in the ucontext 5 reference page Alternatively your signal handler can have this prototype void name int sig int code struct sigcontext sc The second argument gives some added information about the signal see signal 5 for a list of codes The third argument a pointer to a sigcontext_t object gives the machine state at the time the signal was delivered in slightly different form from the ucontext_t 123 Chapter 5 Signalling Events 124 When you use sigaction to set up a signal handler you pass an argument structure containing option flags that affect the treatment of the signal SA_SIGINFO SA_ONSTACK SA_RESETHAND SA_NODEFER SA_RESTART When set you are specifying asynchronous handling and your handler uses the POSIX prototype Its address is passed in the sa_sigaction structure field When not set a handler uses the older prototype and its address is passed in sa_handler When set your handler is called using alternate stack memory you have previously assigned with sigaltstack Otherwise the handler uses the stack of the process or thread stack executing at the time of the signal When set the policy for this signal is reset to the default when your handler is called Your handler is expected to reestablish the action if that is desired When not set the signal is automatically blocked while your h
297. key_t strtoul optarg NULL 0 break case s size size size_t strtoul optarg NULL 0 break case p permissions perms int strtoul optarg NULL 0 break case c shmflg IPC_CREAT break case x shmflg IPC_EXCL break default unknown or missing argument return 1 shmid shmget key size shmflg perms if 1 shmid printf shmid d 0x x n shmid shmid if 1 shmctl shmid IPC_STAT amp ds printf owner uid gid d d n ds shm_perm uid ds shm_perm gid printf creator uid gid d d n ds shm_perm cuid ds shm_perm cgid else perror shmctl IPC_STAT else perror shmget return errno Example of Attaching a Shared Segment The program in Example 3 6 illustrates the process of actually attaching to and using a shared memory segment The segment must exist and is specified by its ID or by its key You can use the program in Example 3 5 to create a segment for this program to use 74 System V Shared Memory Functions The attachment is either read write or read only depending on the presence of the r command parameter When the program attaches the segment read write it stores its own PID in the first word of the segment Run the program several times each time it reports the previous PID value and sets anew PID value This illustrates that the contents of the segment persist between uses of the segment You ca
298. ks using F_GETLK instead of F_GETLKW Enforcing Mandatory Locking 190 File locking is usually an in memory service of the IRIX kernel The kernel keeps a table of locks that have been placed Processes anywhere in the system update the table by calling fentlQ or lockf to request locks When all processes that use a file do this and respect the results file integrity can be maintained It is possible to extend file locking by making it mandatory on all processes whether or not they were designed to be part of the cooperating group Mandatory locking is enforced by the file I O function calls As a result an independent process that calls write to update a locked record is blocked or receives an error code The write and other system functions test for a contending lock on a file that has mandatory locking applied The test is made for every operation on that file When the caller is a process that is cooperating in the lock and has already set an appropriate lock the mandatory test is unnecessary overhead Enforcing Mandatory Locking Mandatory locking is enforced on a file by file basis triggered by a bit in the file inode that is set by chmod see the chmod 1 and chmod 2 reference pages In order to enforce mandatory locking on a particular file turn on the set group ID bit along with a nonexecutable group permission as in these examples which are equivalent chmod 2644 target file chmod 1 target file The bit
299. l overview of parallel programming models and of the hardware that they use The parallel models are discussed in more detail in following chapters 243 Chapter 10 Models of Parallel Computation Parallel Hardware Models 244 Silicon Graphics makes a variety of systems The O2 Indy and Indigo workstations have single CPUs Although they can perform I O operations in parallel with computing they can execute only one stream of instructions at a time and time share the CPU across all active processes The CHALLENGE and Onyx systems and their POWER versions are symmetric multiprocessor SMP computers In these systems at least 2 and as many as 36 identical microprocessors access a single common memory and a common set of peripherals through a high speed bus The OCTANE workstation is a two CPU SMP The POWER CHALLENGEarray comprises 2 or more POWER CHALLENGE systems connected by a high speed local HIPPI network Each node in the array is an SMP with 2 to 36 CPUs Nodes do not share a common memory communication between programs in different nodes passes through sockets However the entire array can be administered and programmed as a single entity An Origin2000 system provides nodes each containing two or four CPUs connected in systems of 2 to 128 nodes by a high speed connection fabric All system memory is uniformly addressable but there is a time penalty for the use of nonlocal memory see Using Origin2000 Nonun
300. l segment of memory pages Data stored by one is immediately visible to the other This is the most basic method of sharing a memory segment More elaborate methods with additional services are discussed in Chapter 3 Sharing Memory Between Processes Mapping a Segment of Zeros You can use mmap to create a segment of zero filled memory Create a file descriptor by applying open to the special device file dev zero Map this descriptor with addr of 0 off of 0 and len set to the segment size you want A segment created this way cannot be shared between unrelated processes However it can be shared among any processes that share access to the original file descriptor that is processes created with sproc using the PR_SFDS flag see the sproc 2 reference page For more information about dev zero see the zero 7 reference page 19 Chapter 1 Process Address Space 20 The difference between using mmap of dev zero and calloc is that calloc defines all pages of the segment immediately When you specify MAP_AUTOGROW mmap does not actually define a page of the segment until the page is accessed You can create a very large segment and yet consume swap space in proportion to the pages actually used Note This feature is unique to IRIX The file dev zero may not exist in other versions of UNIX Since the feature is nonportable you should not use the POSIX function shm_open with dev zero or any device special
301. lags defaults ok oflags O_RDONLY shm_fd ity of else 1 shm_open path oflags perms shm_fd attach mmap NULL size mprot mflags shm_fd off_t 0 LE else perr attach MAP_FAILED mmap worked printf Attached at Ox lx first word 0x lx n attach pid_t attach if mprot amp PROT_WRITE pid_t attach getpid printf Set first word to 0x 1lx n pid_t attach if wopt wait a while report possibly different value char inp 80 printf Waiting for return key before unmapping gets inp printf First word is now 0x 1lx n pid_t attach if munmap attach size perror munmap perror mmap or shm_open return errno IRIX Shared Memory Arenas IRIX Shared Memory Arenas The shared memory arena is basic to all IRIX IPC mechanisms IRIX semaphores locks and barriers are all represented as objects within a shared arena Overview of Shared Arenas A shared arena is a segment of memory that can be made part of the address space of more than one process Each shared arena is associated with a disk file that acts as a backing store for the file see Page Validation on page 9 Each process that wants to share access to the arena does so by specifying the file pathname of the file The file pathname acts as the public name of the memory segment The file
302. languages and other codesets It should be noted that the sorting in en_US locale is different from sorting in C locale As a result en_US is not equal to C locale Furthermore e Sorting order for a language may be completely unrelated to the numerical order of the characters in a given encoding e Even with a correctly sorted list of the characters in a character set you may not be able to sort words properly e Locales using identically encoded character sets may use very different sorting rules Programs using ASCII can do simple arithmetic on characters and directly calculate sorting relationships such programs frequently rely on truisms such as the fact that ral lt Tht in ASCII But internationalized programs cannot rely on ASCII and English sorting rules Consider some non English collation rule types e One to Two mappings collate certain characters as if they were two For example the German collates as if it were ss e Many to One mappings collate a string of characters as if they were one For example Spanish sorts ch as one character following c and preceding d In Spanish the following list is in correct alphabetical order calle creo chocolate decir e Don t Care Character rules collate certain characters as if they were not present For example if were a don t care character co op and coop would sort identically e First Vowel rules sort words based fir
303. larger ones although you should not write code that depends on this Tip The boundaries of all distributed DSOs are declared in the file usr lib so_locations When IRIX loads a DSO that is not declared in this file it seeks a segment of the address space that does not overlap any declared DSO and that will not interfere with growth of the stack segment To learn more about DSOs see the rld 1 and dso 5 reference pages and the MIPSpro Compiling Linking and Performance Tuning Guide Defining the Address Space Page Numbers and Offsets IRIX manages memory in units of a page The size of a page can differ from one system to another In systems such as the O2 workstation which support only 32 bit addressing the page size is always 4 096 bytes In each 32 bit virtual address e the least significant 12 bits specify an offset from 0 to OxOfff within a page e the most significant 20 bits specify a virtual page number VPN In systems that support 64 bit addressing the page size is greater than 4 096 bytes The page size is configurable and in fact different programs can have different page sizes and a single program can have different size pages for the text segment stack segment and data segments However the page size is always a power of 2 and the bits of the virtual address are used in the same way the least significant bits of an address specify an offset within a page while the most significant bits specify the VPN You can
304. ld_t pc gt child_t of current file void method void size_t inProc0O gt chosen input method char arenaPath 128 build area for arena pathname char outPath 128 build area for output pathname Ensure the name of a temporary directory ay tmpdir getenv TMPDIR if tmpdir tmpdir var tmp Build a name for the arena file ES strcpy arenaPath tmpdir strcat arenaPath aiocat wrk Create the arena First call usconfig to establish the minimum siz twice the buffer size per file to allow for misc usage and the maximum number of processes that may later use this arena For this program that is MAX_INFILES 10 allowing for our sprocs plus those done by aio_sgi_init These values apply to any arenas made subsequently until changed 213 Chapter 8 Using Asynchronous I O ptrdiff_t ret ret usconfig CONF_INITSIZE 2 BLOCKSIZE MAX_INFIL I QUITIFMONE ret usconfig size ret usconfig CONF_INITUSERS MAX_INFILES 10 QUITIFMONE ret usconfig users arena usinit arenaPath QUITIFNULL arena usinit EJ Nn E Allocate the barrier xi convene new_barrier arena QUITIFNULL convene new_barrier Allocate the array of child info structs and zero it EY array child_t usmalloc MAX_INFILES sizeof child_t arena QUITIFNULL array usmalloc
305. le 16 6 Table 16 7 Table 16 8 Table 16 9 Table 16 10 Table 16 11 Table A 1 Functions for Using Condition Variables 294 Functions for Preparing Read Write Locks 298 Functions for Using Read Write Locks 299 Font and Font Metric Directories 319 Locale Categories 341 Category Environment Variables 342 Some Monetary Formats 356 ANSI Compatible Functions 361 X Open Additional Functions 362 Regular Expression Libraries in IRIX 365 Character Expressions in Internationalized Regular Expressions 366 Examples of Internationalized Regular Expressions 367 Cultural Data Names Categories and Settings 368 ISO 8859 Character Sets 410 Character Sets for Asian Languages 412 ISO 3166 Country Codes 415 XXxi About This Manual This manual discusses several topics of interest to programmers writing applications for the IRIX operating system on Silicon Graphics computers These topics include memory management interprocess communication models of parallel computation file and record locking font access and internationalization What This Manual Contains This manual contains the following major parts Part I The Process Address Space tells how the virtual address space of a process is created and how objects are mapped into it Part II Interprocess Communication covers all the facilities for communicating and coordinating among processes such as semaphores shared memory signals message queues and file an
306. le call To do this you specify an array containing more than one operation structure The semop function performs each operation in sequence IRIX Facilities for Mutual Exclusion You can use this feature for example to claim multiple resources each represented by a different semaphore Your array would specify the P operation on each of the semaphores in sequence When semop returns successfully you own all the resources A similar multiple V operation returns all the resources at once The IPC_NOWAIT and SEM_UNDO flags are important when claiming multiple resources at once Specify SEM_UNDO on all operations and specify IPC_NOWAIT on all but the first one If the second or later resource is unavailable semop restores all preceding claims and returns an error code As long as all processes or threads operate on semaphores in the same order this logic prevents deadlocks and it avoids long fruitless suspensions Example Programs The programs in this section allow you to experiment with semaphore sets from the command line e Example 4 3 on page 102 can be used to experiment with semget creating semaphore sets with different sizes and permissions e Example 4 4 on page 104 can be used to test semctl for displaying and changing owner IDs and permissions e Example 4 5 on page 106 can be used to test semctl for sampling the values of semaphores or to display the state of a semaphore set e Example 4 6 on page 108
307. le files To display the current X font path enter this command xset q In addition to other information the xset utility displays font path information that may look like this Font Path usr lib X11 fonts 100dpi usr lib X11 fonts 75dpi usr lib X11 fonts misc usr lib X11 fonts Typel usr 1lib X11 fonts Speedo usr lib X11 fonts CID The X Window System checks the resolution of your video monitor If that resolution is closer to 75 dpi than 100 dpi it puts the directory 75dpi ahead of the directory 100dpi in the X font path Changing the X Font Path You can change the default X font path by using the option fp on an xset command line For example enter xset fp newpath This command changes the X font path to the new font path newpath Installing and Adding Font and Font Metric Files Installing and Adding Font and Font Metric Files This section explains where the various types of font and font metric files are installed by default and how you can add one of your font or font metric files to the IRIX operating system This section describes the following topics e Locations of Font and Font Metric Files covers the conventional directories and names for font files e Adding Font and Font Metric Files details adding a bitmap and outline font and adding a font metric file Locations of Font and Font Metric Files By default font and font metric files are installed in the directories li
308. le parameter indicates that the locale should be chosen based on the value of the environment variable LC_COLLATE or if that value is undefined the value of the environment variable LANG which should contain the name of the locale that the user wishes to work in Table 16 2 Category Environment Variables Category First Environment Variable Second Environment Variable LC_COLLATE LC_COLLATE LANG LC_CTYPE LC_CTYPE LANG LC_MESSAGES LC_MESSAGES LANG LC_MONETARY LC MONETARY LANG LC_NUMERIC LC_NUMERIC LANG LC_TIME LC_TIME LANG Specifying the category LC_ALL attempts to set each category individually to the value of the appropriate environment variable If no non null environment variable is available setlocale returns the name of the current locale Using Locales Nonempty Strings in Calls to setlocale Here are the possibilities for specifying the locale parameter NULL Specifying a null pointer argument not the same as the empty string causes setlocale to return the name of the current locale C Specifying a locale value of the single character string C requests whatever locale the system uses as a default Note that this is a string and not just a character Other strings Request a particular locale by specifying its name This overrides any user preferences and should only be done with good reason Location of Locale Specific Data Except for XPG 4 message catalogs locale specific data
309. learn the actual size of a page in the present system with getpagesize as noted under Interrogating the Memory System on page 11 Page tables built by IRIX during a fork or exec call define the address space for a process by specifying which VPNs are defined These tables are consulted by the hardware Recently used table entries are cached for instant lookup in the processor chip in an array called the Translation Lookaside Buffer TLB Address Definition Most of the possible addresses in an address space are undefined that is not defined in the page tables not related to contents of any kind and not available for use A reference to an undefined address causes a SIGSEGV error Addresses are defined that is made available for potential use in one of five ways Fork When a process is created using fork the new process is given a duplicate copy of the parent process s page table so that any addresses that were defined in the parent s address space are defined the same way in the address space of the new process See the fork 2 reference page Exec The exec function creates a new address space in which to execute a specified program or interpreter See the exec 2 reference page Chapter 1 Process Address Space Stack The call stack is created and extended automatically When a function is entered and more stack space is needed IRIX makes the stack segment larger defining new addresses if required
310. letes If any more operations are pending it initiates one A function that initiates one selected pending operation It prepares the aiocb structure including the specification of yeahWeFinishedOne as the callback function The lock dontTouchThatStuff must be held before this function is called Note The code in Example 8 3 is not intended to be realistic and is not recommended as a model In order to demonstrate the use of callback functions and the aiocb it essentially duplicates work that could be done by the lio_listio feature of asynchronous I O 205 Chapter 8 Using Asynchronous I O Example 8 3 Set of Functions to Schedule Asynchronous I O define _ABT SOURCE include lt signal h gt include lt aio h gt include lt ulocks h gt define MAX PENDING 10 define STATUS_EMPTY 0 define STATUS_ACTIVE 1 define STATUS_PENDING 2 static struct onePendingIO int status int theFile void theData off_t theSize off_t theSeek int readNotWrite pendinglO MAX_PENDING static unsigned numPending static struct aiocb theAiocb static ulock_t dontTouchThatStuff static unsigned scanner static void initiatePending int P static void yeahWeFinishedOne union sigval S ussetlock dontTouchThatStuff pendingIO S sival_int status STATUS_EMPTY if numPending while pendingIO scanner status STATUS_PENDING if scanner gt MAX_PENDING scan
311. limit exceeded see getrlimit 2 and Terminate Terminate write 2 Unassigned do not use POSIX real time signal range Although SIGUSR1 and SIGUSR2 are nominally defined by the you for your program s purposes they are also used by different application packages for special signals For example if you set a file lock on an NFS mounted file the NFS lock daemon may send SIGUSR1 see NFS File Locking on page 192 Signal Implementations There are three UNIX traditions for signals and IRIX supports all three They differ in the library calls used in the range of signals allowed and in the details of signal delivery The basic signal operations and the implementing functions are summarized in Table 5 2 Table 5 2 Signal Handling Interfaces Function POSIX Functions SVR4 Functions BSD 4 2 Functions Set and query signal sigaction 2 sigset 2 sigvec 3 handler sigsetops 3 signal 2 signal 3 sigaltstack 2 Send a signal sigqueue 2 sigsend 2 kill 3 kill 2 kill 2 killpg 3 pthread_kill 3P Temporarily block sigprocmask 2 sighold 2 sigblock 3 specified signals pthread_sigmask 3P sigrelse 2 sigsetmask 3 Query pending signals sigpending 2 n a n a Signals Table 5 2 Signal Handling Interfaces continued Function POSIX Functions SVR4 Functions BSD 4 2 Functions Wait fora signal handler sigsuspend 2 sigpause 2 sigpause 3 to be invoked Wait for a signal and sigwait 2 n a n a receive sy
312. lizing Your Application 410 The ISO 8859 Family American English is easily representable in 7 bit ASCII Most other languages are not For example the character is not in ASCII Most Western European languages are representable in 8 bit ISO 8859 1 which is commonly known as Latin 1 Latin 1 is a superset of ASCII that includes characters used by several Western European languages such as 6 2 ISO 8859 comes in nine parts many of which overlap all are supersets of ASCII The ISO 8859 Character Sets are shown in Table 16 10 Table 16 10 ISO 8859 Character Sets Character Set 8859 1 8859 2 8859 3 8859 4 8859 5 8859 6 8859 7 8859 8 8859 9 Common Name Latin 1 Latin 2 Latin 3 Latin 4 Latin Cyrillic Latin Arabic Latin Greek Latin Hebrew Latin 5 Languages Supported Danish Dutch English Faeroese Finnish French German Icelandic Irish Italian Norwegian Portuguese Spanish Swedish Albanian Czech English German Hungarian Polish Rumanian Serbo Croatian Slovak Slovene Afrikaans Catalan Dutch English Esperanto German Italian Maltese Spanish Turkish Danish English Estonian Finnish German Greenlandic Lapp Latvian Lithuanian Norwegian Swedish Bulgarian Byelorussian English Macedonian Russian Serbo Croatian Ukrainian Arabic English see ISO 8859 6 specification English Greek see ISO 8859 7 specification English
313. llating Sequence Tables Collating sequence tables define the collating sequence for each supported language The binary values of characters in the associated coded character set are used as indices into the table individual entries of which indicate the relative position of that character in the language collating sequence The interface definition supports the following capabilities e one to one character mappings e one to two character mappings where certain characters require treatment as if they were two characters e n to one character mappings where certain character sequences require treatment as if they represented a single character in the collating sequence The maximum value of N is defined separately for each supported language where N is a number in the range 1 NL_NMAX e don t care characters where certain characters are ignored by the collating sequence These capabilities extend to providing support for the relative ordering of collating elements within an equivalent class for example where two characters are first compared for equality ignoring accents and if equal are then ordered by accent sequence Character Classification Tables These contain the lookup tables for character classification Each character code from the defined coded character set is used as an index into the relevant language lookup table Each entry language lookup table contains a series of flags identifying the truth or falsehood of a
314. lly there is no support for setting the entire signal mask in one operation The semantics of SVR3 compatible signal established with signal are not desirable for most programs When control enters a signal handler you established using signal the handling of that same signal is set to default and that signal remains unblocked Your signal handler can use signal to reestablish itself as the handler or it can use sighold to block the signal However even if these actions are the first statements of the handler function there is a period of time at the beginning of the handler during which a second signal of the same type could be received If this occurs the second signal receives default handling and is not seen by your handler You can avoid this problem by using the SVR4 function sigset instead of signal to establish a handler Before a handler established by sigset is called that signal is blocked until the handler returns and the signal disposition is not reset to default 125 Chapter 5 Signalling Events 126 BSD Signal Facility The BSD signal facility is compatible with code ported from the BSD 4 2 distribution Table 5 5 summarizes the functions you use to manage signals with this interface Note In order to use any of the functions in Table 5 5 you must define one of the compiler variables _BSD_SIGNALS or _BSD_COMPAT prior to the inclusion of the header file signal h You can do this directly in the sour
315. lly in any link by the cc command and in the libmpce library which you include with Impce IRIX IPC functions all require the use of a shared arena a segment of memory that can be mapped into the address spaces of multiple processes The first step in preparing to use any IRIX IPC object is to create a shared arena as documented under Initializing Arena Attributes on page 61 A shared arena is identified with a file that acts as the backing store for the arena memory Communicating processes gain access to the arena by specifying its filename All processes using the same arena have access to the same set of IPC objects This makes it relatively easy for unrelated processes to communicate using IRIX IPC they only have to know the filename of the arena to gain access IRIX supports SVR4 functions for signals shared memory semaphores message queues and file locking To use them you need to include the correct header files when compiling The header files required for each function are listed in the reference pages for the functions System V functions are primarily kernel functions No special library linkage is required to access them There is general discussion of SVR4 IPC operations in the intro 2 reference page 49 Chapter 2 Interprocess Communication 50 SVR4 IPC Name Space All SVR4 IPC objects are named in a special IPC name space An object such as a shared memory segment or message queue is named by a numer
316. lp from X when attempting multilingual support No locales or special process states are peculiar to X This section covers the following topics e Limitations of X11R6 in Supporting Internationalization discusses vertical text character sets and Xlib interface changes e Resource Names covers encoding of resource names e Getting X Internationalization Started describes initialization of Xlib and toolkit programming e Fontsets explains specifying creating and using fontsets e Text Rendering Routines discusses the XmbDrawText XmbDrawString and XmbDrawlmageString functions e New Text Extents Functions describes a few new extents related functions including XFontSetExtents Limitations of X11R6 in Supporting Internationalization Since X is locale independent there are some limitations on its ability to support internationalization The X protocol and Xlib specification together with ANSI C and POSIX restrictions have led to certain choices being made in X11R6 These are described in the following paragraphs 383 Chapter 16 Internationalizing Your Application 384 Vertical Text There is no built in support for vertical text Applications may draw strings vertically only by laying out the text manually Character Sets In previous releases of X there was no general support for character sets other than Latin 1 X11R6 however does allow other character sets X11R
317. ls When you are writing a pthreads program you should use only the POSIX signal facilities see POSIX Signal Facility on page 120 Pthreads and Signals Setting Signal Masks Each thread has a signal mask that specifies the signals it is willing to receive see Signal Blocking and Signal Masks on page 117 In a program that is linked with the pthreads library this should be changed using pthread_sigmask Each thread inherits the signal mask of the thread that calls pthread_create Typically you set an initial mask in the first thread so that it can be inherited by all other threads Note In IRIX you can use sigprocmask instead of pthread_sigmask but it may not be portable to other systems When a signal is directed to a specific thread that is blocking the signal the signal remains pending on the thread until that thread unblocks it When a signal is directed to a process it is delivered to the first thread that is not blocking that signal If all threads block that signal the signal remains pending on the process until some thread unblocks it or the process terminates A thread can find out which signals are pending by calling sigpending This function returns a mask showing the set of signals pending on the process as a whole or for the calling thread that is the signals that could be delivered to the calling thread if they were not blocked Setting Signal Actions When a signal is delivered some acti
318. m any process The OCTANE workstation also uses a single common memory that is accessible from either of its CPUs in the same amount of time The effect of a single common memory is that processes running in different CPUs can share memory and can update the identical memory locations concurrently For example suppose there are four CPUs available to a Fortran program that processes a large array of data You can divide a single DO loop so that it executes concurrently on the four CPUs each CPU working in one fourth of the array in memory As another example IRIX allows processes to map a single segment of memory into the virtual address spaces of two or more concurrent processes see Chapter 3 Sharing Memory Between Processes Two processes can transfer data at memory speeds one putting the data into a mapped segment and the other process taking the data out They can coordinate their access to the data using semaphores located in the shared segment see Chapter 4 Mutual Exclusion Multiple Memory Systems In an Array system such as a POWER CHALLENGEarray each node is a computer built on the CHALLENGE Onyx architecture However the only connection between nodes is the high speed HIPPI bus between nodes The system does not offer a single system memory instead there is a separate memory subsystem in each node The effect is that e There is not a single address map A word of memory in one node cannot be addressed at
319. maintains a single uniform physical address space Each CPU translates memory addresses from virtual to physical and presents the physical address to its hub A few high order bits in the physical address designate the node where the physical memory is found The hub uses these bits to direct the memory request as required to the local memory in its own node or through a router to another node Using Origin2000 Nonuniform Memory All translation and routing of physical addresses is entirely transparent to software which operates in a uniform virtual memory space Two aspects of memory mapping are not uniform First the physical memory map can contain gaps Not all nodes have the same amount of memory installed Indeed there is no requirement that all nodes be present in the system and in future releases of IRIX it will be possible to remove and replace nodes while the system remains up Second the access time to memory differs depending on the distance between the memory and the CPU that requests it e Memory in the same node is accessed fastest e Memory located on another node in the same module costs one or two router hops e Memory in another module costs additional router hops Normally memory location relative to a program has an insignificant effect on performance because e IRIX takes is careful to locate a process in a CPU near the process s data e Most programs are so written that 90 or more of the memory accesses
320. maps and you can use Unicode codes to access characters in those fonts Installing and Adding Font and Font Metric Files Conventions for Bitmap Font Filenames The names of bitmap font files are specified according to the following conventions e Most filenames begin with three or four letters unique to the font family such as cour for the Courier family or 8x13 for a utility bitmap family e When a family has different style variants such as Roman and Italic the next character of the filename is an uppercase letter to indicate the style for example courO for Courier Oblique or 8x13B for a utility bold font e The last two characters of the filename are two digits giving the nominal size of the font in points as in courO18 e Most bitmap files are of the Portable Compiled Format PCF type and have the file suffix pcf as in courO18 pef or 8x13B pcf e Files are compressed using the compress command see the compress 1 reference page and therefore have the terminal suffix Z as in courO18 pcf Z e Exceptions to these conventions are names such as Swiss721 Bold Bitstream Unicode 0_10 pcf Z which are bitmap fonts in the directory usr lib X11 fonts 100dpi These fonts use this format CIDFontName CMapName_PointSize pcf Z where CIDFontName is the font family name CMapName specifies the character map name and PointSize is the nominal size of the font These names are reserved for bitmap CID keyed fonts In usr lib
321. mation If you can t use dynamic layout objects refer to Layout on page 408 for instructions 21 Make sure that all icons and other pictographic representations used by your application are localizable See Icons on page 409 for more information Additional Reading on Internationalization For more information on internationalization refer to e OReilly Volume 1 Xlib Programming Manual e X Window System by Robert Scheifler and Jim Gettys e X Open Portability Guide e OSE Motif Style Guide 339 Chapter 16 Internationalizing Your Application Using Locales 340 An internationalized system is capable of presenting and receiving data understandably in anumber of different formats cultures languages and character sets An application running in an internationalized system must indicate how it wants the system to behave IRIX uses the concept of a locale to convey that information A process can have only one locale at a time Most internationalization interfaces rely on the locale of the current process being set properly the locale governs the behavior of certain library routines This section covers the following topics e Setting the Current Locale explains categories locales strings location of locale specific data and locale naming conventions e Limitations of the Locale System describes multilingual support misuses of locales and encoding You can find additional information in
322. mber of processes to be for use in initializing aio and for use by each child in a barrier call Asynchronous I O Example af nprocs lt nfiles Initialize async I O using aio_sgi_init in order to specify a number of locks at least equal to the number of child procs and in order to specify extra sproc users GA aioinit_t ainit 0 all fields initially zero Go with the default 5 for the number of aio created procs as we have no way of knowing the number of unique devices Af define AIO_PROCS 5 ainit aio_threads AIO_PROCS Set the number of locks aio needs to the number of procs we will start minimum 3 ainit aio_locks nprocs gt 2 nprocs 3 Warn aio of the number of user procs that will be using its arena xf ainit aio_numusers nprocs aio_sgi_init amp ainit Process each input file either in a child process or in a subroutine call as specified by the DO_SPROCS variable z for argno 0 argno lt nfiles argno pc amp array argno if DO_SPROCS define CHILD_STACK 64 1024 For each input file start a child process as an instance of the selected method a argument If an error occurs quit That will send a SIGHUP to any already started child which will kill it too 217 Chapter 8 Using Asynchronous I O else endif if DO_ I ay pc gt procid s
323. me form as a disk filename and in fact a queue is implemented as a file This implementation is permitted but not required by the POSIX standard Other implementations might not use it Once created a queue is a persistent object that survives until removed If you want the program to create a queue use it and then remove it during termination you can call mq_unlink to remove the queue 141 Chapter 6 Message Queues 142 The file can retain some queued messages when the queue is not open so that some queued data can persist beyond the termination of the programs that use the queue The queued data cannot be trusted after a reboot because the data might not have been written to disk before the system came down You should not depend on the state of the message queue after a reboot Opening an Existing Queue It is more common to open an existing queue When the program expects the queue to exist it omits the O_CREAT flag bit An error is returned if the queue does not exist or if the queue exists but the effective user ID or group ID of the program does not allow access to it The program can specify the O_RDONLY O_WRONLY or O_RDWR flag to show its intended use of the queue Access is controlled by the access permissions of the queue just as for a file Specifying Blocking or Nonblocking Access An important flag when opening a queue is the O_ NONBLOCK flag When the program specifies O_NONBLOCK it wants an immedi
324. me two basic procedures work to allocate any collection of objects For example the semaphore could represent the number of open slots in a ring buffer and the lock could stand for the right to update the ring buffer pointers A LIFO queue can be managed without a lock see Using Compare and Swap on page 93 Semaphores created using POSIX functions and semaphores created by the SVR4 IPC facility can be used to coordinate IRIX processes or POSIX threads Semaphores supported by the IRIX IPC facility can be used to coordinate IRIX processes only Condition Variables A condition variable is a software object that represents the occurrence of an event Typically the event is a software action such as other thread has supplied needed data Condition variable support is included in the POSIX pthreads library and can be used only to coordinate among POSIX threads not between IRIX processes See Chapter 13 Thread Level Parallelism for information on the pthread library A thread that wants to wait for an event claims the condition variable which causes the thread to wait The thread that recognizes the event signals the condition variable releasing one or all threads that are waiting for the event 81 Chapter 4 Mutual Exclusion In the expected mode of use there is a shared resource that can be depleted Access to the resource is represented by a mutex A thread claims the mutex but then finds that the shared res
325. mod buffered default synchronous or direct b bsize blocksize for each write default 512 n recs how many writes to do default 1000 i display info from fcntl F_DIOINFO xy include lt errno h gt for perror include lt stdio h gt for printf include lt stdlib h gt for getenv malloc 3c include lt sys types h gt required by open include lt unistd h gt getopt open write include lt sys stat h gt ditto include lt fcntl h gt open and fentl int main int argc char argv char tmpdir gt name string of temp dir char ofile NULL argument name of file path int oflag 0 m b s d result size_t bsize 512 blocksize void buffer aligned buffer int nwrites 1000 number of writes int ofd file descriptor from open int info 0 i option default 0 int CF scratch var for getopt char outpath 128 build area for output pathname struct dioattr dio Get the options ay while 1 232 c getopt argc argv o m b n i Using Direct I O switch c case o o outfile ofile optarg break case m m mode switch optarg case b m b buffered i e normal oflag 0 break case s m s synchronous but not direct oflag O_SYNC break case d md direct oflag O_DIRECT break default
326. mode mode_t perms if uid l 1L buf msg_perm uid uid_t uid if gid 1L buf msg_perm gid gid_t gid if bytes 1L buf msg_qbytes ulong_t bytes if 1 msgctl msqid IPC_SET amp buf perror nmsgct1 IPC_SET printf owner d d perms 040 max bytes d n buf msg_perm uid buf msg_perm gid buf msg_perm mode buf msg_qbytes printf Sd msgs d bytes on queue n buf msg_qnum buf msg_cbytes else perror nmsgct1 IPC_STAT else perror msgget 165 Chapter 6 Message Queues 166 Example of msgsnd The msgsnd program in Example 6 7 allows you to send one or more messages of specified length and type to a message queue The following command line arguments are supported k key Numeric identifier of a message queue for example k 99 iid Message queue ID alternative to specifying the key for example i 80 c count Number of messages to send The default is 1 t type Numeric type of message to send Types less than 1 are rejected by msgsnd b bytes Size of each message for example b 0x200 n Use the IPC_NOWAIT flag with msgsnd The program sends as many messages as you specify each with the specified type and size The first 32 bytes of each message is a printable string containing a sequence number and the date and time The message is padded out to the specified size with binary 0 System V Message Queues Example 6 7
327. n and is predictable If the application creates the object each time the application starts up the key is always the same The ID number is arbitrary and a new ID is created each time an object is created A process can gain access to an object based on either number the key or the ID For example an SVR4 shared memory segment has a key and an ID The shmget function takes a key and returns the corresponding ID The ID is used to attach the segment However if a process knows the ID it can simply use it without first calling shmget to obtain it 51 Chapter 2 Interprocess Communication Using 4 2 BSD IPC 52 Private Key Values When creating an IPC object you can specify a key of KEY_PRIVATE 0 This causes an object to be created and recorded in the IPC name space with a key of 0 The created object cannot be accessed from another process by key because if another process uses KEY_PRIVATE it creates its own object However another process can access a key private object using the object s ID number You can use the KEY_PRIVATE feature when you want to create an IPC object for use within a single process or share group a share group is the set of processes that share one address space see Process Creation and Share Groups on page 262 The IPC object can be used within the share group based on its address or by ID number Because it has no key it cannot be used outside the share group The 4 2 BSD function
328. n aioinit amp A When to Initialize The time at which initialization occurs is important If you initialize in a process that has been assigned to run on an isolated CPU the asynchronous I O processes will also run on that CPU You probably want the I O processes to run under normal dispatching on unrestricted CPUs In that case the proper sequence of initialization is e Open all file descriptors and verify that files and devices are ready e Initialize asynchronous I O The lightweight processes created by aioinit inherit the attributes of the calling process including its current priority and access to open file descriptors e Isolate any CPUs that are to be dedicated e Create child processes and assign them to their CPUs The asynchronous I O processes created by aioinit continue to be scheduled according to their priority in whatever CPUs remain available Scheduling Asynchronous I O You schedule an input or output operation by calling aio_read or aio_write passing an aiocb structure to describe the operation see the aio_read 3 and aio_write 3 reference pages The operation is queued to that file descriptor It will be executed when one of the asynchronous I O processes or threads is available The return code from the library call says nothing about the I O operation itself it merely indicates whether or not the aiocb could be queued About Synchronous and Asynchronous I O Note It is important to use a
329. n attempt is made to send a message that is larger than the queue maximum size mq_send b 129 var tmp Q32x128 mq_send Inappropriate message buffer length A message of appropriate size is sent Its presence on the queue is verified using mq_getattr mq_send b 128 p 7 var tmp Q32x128 mq attr var tmp Q32x128 flags 0x0 maxmsg 32 msgsize 128 curmsgs 1 An attempt is made to send a message with an illegal priority 32 is the highest allowed mq send p 99 var tmp Q32x128 mq_send Invalid argument A message is sent with a valid priority mq_send p 19 var tmp Q32x128 mq attr var tmp Q32x128 flags 0x0 maxmsg 32 msgsize 128 curmsgs 2 The two messages are received The one with higher priority is received first mq _ receive c 2 var tmp Q32x128 1 priority 19 len 63 text 00001 Fri Jun 14 09 19 12 1996 2 priority 7 len 128 text 00001 Fri Jun 14 09 17 15 1996 Another message is requested Since the O_NONBLOCK flag is used the absence of any message is reported as an error code rather than suspending the process mq receive n var tmp Q32x128 mq_receive Resource temporarily unavailable Example of mq_getattr The program mq_attr in Example 6 1 uses mq_getattr to get and display the queue attributes Only one command line argument is accepted path The file pathname of the queue must be given following all options 145 Chapter 6 Message Queues 146 Example 6 1 Program
330. n order to be compatible with a variety of historic UNIX systems the IRIX Developer s Option includes the unique regular expression library sets listed in Table 16 6 Note that only the last wsregexp supports internationalization Table 16 6 Regular Expression Libraries in IRIX Library Documentation Type of Support Provided regcemp 3G Function regcmp compiles a pattern string regex applies the pattern to a target string Syntax is said to be that of ed but syntax and semantics have been changed slightly in unspecified ways regcmp 1 Command applies regcemp against a file of pattern strings generating C code for literal strings that can be included in a source program to preclude having to compile patterns at run time REGEX 3 Function re_comp compiles a pattern string re_exec applies the last compiled pattern against a target string No means of storing compiled patterns No documentation of supported syntax but cross references ed 1 with which it may or may not be compatible regexp 5 Function compile compiles a pattern string step or advance applies a stored pattern against a target string Unusual interface compiles these functions directly into your source module using macro functions you must define Pattern syntax clearly documented wsregexp 3W Function wsrecompile compiles a pattern string wsrestep or wsrematch applies a pattern against a target Both pattern and target strings are w
331. n use the w parameter to have the program wait after attaching This allows you to start more copies of the program so that multiple processes have attached the segment Example 3 6 shmat System Call Example Program to test shmat shmat k lt key gt i lt id gt a lt addr gt r w k lt key gt the key to use to get an ID i lt id gt or the ID to use a lt addr gt address to attach default 0 i attach read only default read write w wait on keyboard input before detaching include lt unistd h gt for getopt include lt sys shm h gt for shmget etc include lt errno h gt errno and perror include lt stdio h gt int main int argc char argv key_t key 1 key int shmid 1 or ID void addr 0 address to request void attach address gotten int rwflag 0 read or r w int wait 0 wait before detach int c ret whil f Ce getopt argc argv k i a rw switch c case k key key key_t strtoul optarg NULL 0 break case i l id shmid int strtoul optarg NULL 0 break 75 Chapter 3 Sharing Memory Between Processes 76 case a addr addr void strtoul optarg NULL 0 break case r read write rwflag SHM_RDONLY break case w wait wait 1 break default return 1 if 1 shmid key mus
332. n what to pay attention to for a given event XmbLookupString returns a status value in a passed parameter equal to one of the following XLookupKeysym Indicates that the keysym should be checked XLookupChars Indicates that a string has been typed or composed XLookupBoth Means both of the above XLookupNone Means neither is ready for processing XBufferOverflow Means the supplied buffer is too small call XmbLookupString again with a bigger buffer XmbLookupString also returns the length of the string in question Note that XmbLookupString returns the length of the string in bytes while XwcLookupString returns the length of the string in characters The example below should help show how these functions work Most event processors perform a switch on the event type assume you have done that and have received a KeyPress event 405 Chapter 16 Internationalizing Your Application 406 Example 16 13 KeyPress Event case KeyPress EAE Keysym keysym Status status int buflength static int bufsize 16 static char buf NULL if buf NULL buf malloc bufsize if buf lt 0 StopSequence buflength XmbLookupString ic amp event buf bufsize amp keysym amp status first check to see if that worked if status XBufferOverflow buf realloc buf bufsize buflength buflength XmbLookupString ic amp event buf bufsize amp keysym amp status
333. named in the pthread_create call When it returns from that function the thread terminates A thread can terminate earlier by calling pthread_exit In either case the thread returns a value of type void One thread can request early termination of another by calling pthread_cancel passing the thread ID of the target thread A thread can protect itself against cancellation using two built in switches e The pthread_setcancelstate function lets you postpone cancellation indefinitely PTHREAD_CANCEL_DISABLE or permit cancellation PTHREAD_CANCEL_ENABLE e The pthread_setcanceltype function lets you decide when cancellation will take place if it is allowed at all Cancellation can happen whenever it is requested PTHREAD_CANCEL_ASYNCHRONOUS or only at defined points PTHREAD_CANCEL_DEFERRED Using Thread Unique Data When you prevent cancellation by setting PTHREAD_CANCEL_DISABLE a cancellation request is blocked but remains pending until the thread terminates or changes its cancellation state The initial cancellation state of a thread is PTHREAD_CANCEL_ENABLE and the type is PTHREAD_CANCEL_DEFERRED In this state a cancellation request is blocked until the thread calls a function that is a defined cancellation point The functions that are cancellation points are listed in the pthread_setcanceltype 3P reference page A thread can explicitly permit cancellation by calling pthread_testcancel Joining and Detaching S
334. nchronization objects in the same cache line strategy 3 A lock or semaphore can be in the same cache line as the data that it controls because an update of one usually follows an update of the other strategy 4 Carefully review the design of any data collection that is used by parallel code For example the root and the first few branches of a binary tree or B tree are likely to be visited by every CPU that searches that tree and therefore will be cached by every CPU Elements at higher levels in the tree may be visited and cached by only a few CPUs Other classic data structures can cause cache contention computer science textbooks on data structures are generally still written from the standpoint of a single level mainframe memory architecture For example a hash table can be implemented compactly with only a word or two in each entry But that creates false sharing by putting several table entries which are unrelated by definition in the same cache line To avoid false sharing in a hash table make each table entry a full 128 bytes cache aligned You can take advantage of the extra bytes in each entry to store a list of overflow hits such a list can be quickly scanned because the entire cache line is fetched as one memory access 37 Chapter 1 Process Address Space 38 Getting Optimum Memory Placement Suppose a Fortran program allocates a 1000 by 1000 array of complex numbers By default IRIX places this 16 MB memory all
335. nchronously sigwaitinfo 2 sigtimedwait 2 It is important to not mix these signal facilities Your program should use functions from only one column of Table 5 2 otherwise unexpected results can occur Signal Blocking and Signal Masks Certain ideas are basic to the use of signals One basic idea is that a program can block the delivery of any signal When a signal that is sent to a program is blocked the signal is queued and remains pending until the program unblocks the signal or terminates Certain urgent signals SIGKILL SIGSTOP SIGCONT cannot be blocked You specify which signals are blocked using a signal mask a set of bits in which each bit corresponds to one signal number When a bit in the mask is set on the signal is blocked if it is a signal that can be blocked Each process has a signal mask inherited from its parent process All three interfaces provide ways to set and clear bits in the current signal mask The BSD interface however only lets you mask the first 32 signal numbers listed in Table 5 1 Each POSIX thread has a signal mask also see Setting Signal Masks on page 285 A multithreaded program defined as a program that is linked with libpthread so it uses the pthreads version of the standard library should use the POSIX interface for signal handling Multiple Signals In most cases if a signal of a certain number is pending for a process and another signal of the same number arrives the se
336. ncy in Origin Systems 32 About CC NUMA Performance Issues 33 About Default Memory Location 33 About Large Memory Use 34 About Multithreaded Memory Use 34 Dealing With Cache Contention 34 Detecting Cache Contention 35 Correcting Cache Contention Problems 36 Getting Optimum Memory Placement 38 Detecting Memory Placement Problems 38 Programming Desired Memory Placement 39 Using Compiler Directives for Memory Placement 39 Taking Advantage of First Touch Allocation 40 Using Round Robin Allocation 41 Using Dynamic Page Migration 41 Using Explicit Memory Placement 42 Contents vi Interprocess Communication 45 Types of Interprocess Communication Available 46 Using POSIX IPC 48 POSIX IPC Name Space 48 Using IRIX IPC 49 Using System VIPC 49 SVR4 IPC Name Space 50 Configuring the IPC Name Space 50 Listing and Removing Persistent Objects 50 Access Permissions 51 Choosing and Communicating Key Values 51 Using ID Numbers 51 Private Key Values 52 Using 4 2 BSD IPC 52 Contents Sharing Memory Between Processes 53 Overview of Memory Sharing 53 Shared Memory Based on mmap 54 Sharing Memory Between 32 Bit and 64 Bit Processes 54 POSIX Shared Memory Operations 55 Creating a Shared Object 55 Shared Object Pathname 56 Shared Object Open Flags 56 Shared Object Access Mode 56 Using the Shared Object File Descriptor 57 Using a Shared Object 57 Example Program 57 IRIX Shared Memory Arenas 61 Overview of Shared Arenas 61 Initializing Arena
337. nd Operation sem_open 3 Create or access a named semaphore returning an address sem_close 3 Give up access to a named semaphore releasing a file descriptor sem_unlink 3 Permanently remove a named semaphore The sem_open function takes the following arguments name Name of the semaphore in the form of a file pathname oflag Either zero or O_CREAT or O_CREAT O_EXCL mode The access permissions to apply if the semaphore is created value Initial value of the semaphore Creating a Named Semaphore The POSIX standard leaves it to the implementation whether or not anamed semaphore is represented by a disk file The IRIX implementation does create a file to stand for each named semaphore see POSIX IPC Name Space on page 48 The file that stands for a semaphore takes up no disk space other than the file node in a directory POSIX Facilities for Mutual Exclusion The oflag is used to handle the following cases e Specify 0 to receive an error if the semaphore does not exist that is to require that the semaphore must exist e Specify O_CREAT O_EXCL to receive an error if the semaphore does exist that is to require that the semaphore not exist e Specify O_CREAT to have the semaphore created if necessary When sem_open creates a semaphore it sets the file permissions specified by mode These permissions control access to a semaphore by UID and GID just as for a file See the open 2 and chmod 2 reference page
338. nd Schedule Cession In many instances a program or a process within a multiprocess program needs to suspend execution for a period of time IRIX contains a variety of functions that provide this capability The functions differ in their precision and in their portability Table 5 6 contains a summary Table 5 6 Functions for Timed Suspensions Reference Page Precision Compatibility Operation sched_yield 2 n a POSIX Defer to any processes eligible to run sginap 2 dispatching IRIX Defer to other processes for the specified interval 10ms number of dispatching cycles sleep 3C second POSIX Suspend for a number of seconds or until a signal arrives usleep 3C microsecond IRIX Suspend for a number of microseconds or until a signal arrives nanosleep 2 nanosecond POSIX Suspend for a number of seconds and nanoseconds or until a signal arrives Sometimes you do not want to suspend for any particular amount of time but simply want to make the current process defer to other processes so that any waiting processes receive a chance to run You can achieve this in two ways The IRIX unique function sginap accepts an argument of 0 meaning to defer for the minimum amount of time However sched_yield is a POSIX compliant function for this purpose 127 Chapter 5 Signalling Events 128 Time Data Structures The include files time h and sys time h define several data types and data structures related to time Some of the
339. nd a list of keysyms This list is usually very short Most keys have only one or two engravings on them Using the state byte Xlib chooses a keysym from the list to find out what was engraved on the key the user pressed At this point the client can choose to act on the keysym itself if for instance it was a backspace or it can ask for a character string represented by the keysym or both Generating such a string is tricky it is discussed in Input Methods IMs below Details on X keyboard support can be found in X Window System Third Edition from Digital Press Details on input methods are also available in that book as well as in the Xlib Programming Manual Volume One Composed Characters There are two ways to compose characters that do not exist on a keyboard explicit and implicit It is common for an application to be modal and switch between the two For example Japanese input of kana is often done via implicit composition Users switch between a mode where input is interpreted as romaji Latin characters and a mode where input is translated to kana 393 Chapter 16 Internationalizing Your Application 394 Furthermore both styles may operate simultaneously While an application is supporting implicit composition of certain characters other characters may be composable via explicit composition Not every keystroke produces a character even if the associated keysym normally implies character text T
340. nd syntax is aiocat o outfile a 0 1 2 3 infilename The output file is given by o with STMPDIR aiocat out by default The aio method of waiting for completion is given by a as follows a 0 poll for completion with aio_error default 1 wait for completion with aio_suspend a 2 wait on a semaphore posted from a signal handler 3 wait on a semaphore posted from a callback routine Up to MAX_INFILES input files may be specified Each input file is read in BLOCKSIZE units The output file contains the data from the input files in the order they were specified Thus the output should be the same as cat infilename gt outfile When DO_SPROCS is compiled true all I O is done asynchronously and concurrently using one sproc d process per file Thus ina multiprocessor concurrent input can be done aed 211 Chapter 8 Using Asynchronous I O includ includ includ includ includ includ includ includ includ includ includ includ includ includ define define define define define MAX_INFI define _SGI_MP_SOURCE lt sys time h gt AE lt errno h gt ee lt stdio h gt lt stdlib h gt lt ulocks h gt hk lt bstring h gt lt sys resource h gt lt sys pretl h gt lt sys types h gt lt unistd h gt AE lt sys types h gt lt sys prcetl h gt lt signal h gt lt aio h gt fE BLOCKSIZE 2
341. nd to change the permissions and owner It takes the following arguments on the command line k key Numeric key to identify the semaphore set for example k 99 iid Semaphore ID number alternative to specifying the key p perms Access permissions to apply to the selected set for example p 0664 u uid New user ID for the semaphore owner g gid New group ID for the semaphore owner If only the key or ID is given the program only displays the state of the set When you specify permissions owner or group the program first queries the current information to initialize an information structure Then it inserts the new items you specified and calls semctl with IPC_SET to change the information Example 4 4 Program to Demonstrate semctl for Management d program to test semct1 2 for status ownership and permissions semmod k lt key gt i lt semid gt p lt perms gt u lt user gt g lt group gt k lt key gt the key to use or i lt semid gt the semid to use p lt perms gt permissions to set with IPC_SET u lt uid gt uid to set as owner with IPC_SE g lt gid gt gid to set as owner with IPC_SE lt unistd h gt for getopt lt sys sem h gt for shmget etc lt errno h gt errno and perror lt stdio h gt int argc char argv t key key semid 1 object ID perms popt 0 perms to set if given uid uopt 0 uid to s
342. ndition is signalled e Wake up re acquiring the mutex for the shared resource and rechecking the condition These three actions are combined into one using a condition variable The functions used with condition variables are summarized in Table 13 10 Table 13 10 Functions for Using Condition Variables Function Purpose pthread_cond_wait 3P Wait on a condition variable pthread_cond_timedwait 3P Wait on a condition variable returning with an error after a time limit expires pthread_cond_signal 3P Signal that an awaited event has occurred releasing at least one waiting thread pthread_cond_broadcast 3P Signal that an awaited event has occurred releasing all waiting threads The pthread_cond_wait and pthread_cond_timedwait functions require both a condition variable and a mutex that is owned by the calling thread The mutex is released and the wait begins When the event is signalled or the time limit expires the mutex is reacquired as if by a call to pthread_mutex_lock Synchronizing Pthreads The POSIX standard explicitly warns that it is possible in some cases for a conditional wait to return before the event has been signalled For this reason a conditional wait should always be coded in a loop that tests the shared resource for the needed status These principles are suggested in the code in Example 13 3 which is modeled after an example in the POSIX 1003 1c standard Example 13 3 Use of Conditi
343. ner 0 initiatePending scanner usunsetlock dontTouchThatStuff static void initiatePending int P lock must be held on entry theAiocb aio_fildes pendingIO P theFile theAiocb aio_buf pendingIO P theData theAiocb aio_nbytes pendingIO P theSize 206 About Synchronous and Asynchronous I O theAiocbh aio_offset pendingIO P theSeek theAiocb aio_sigevent sigev_notify SIGEV_CALLBACK theAiocbh aio_sigevent sigev_func yeahWeFinishedOne theAiocb aio_sigevent sigev_value sival_int P if pendingIO P readNotWrite aio_read amp theAiocb else aio_write amp theAiochb pendinglIO P status STATUS_ACTIVE numPending public int scheduleRead int FD void pdata off_t len off_t pos int Jy if numPending gt MAX_PENDING likeTotallyFreakOut ussetlock dontTouchThatStuff for j 0 pendingIO j status STATUS_EMPTY j r pendingIO j theFile FD pendingIO j theData pdata pendingIO j theSize len pendingIO j theSeek pos pendingIO j readNotWrite 1 pendingIO j status STATUS_PENDING if 1 numPending initiatePending j usunsetlock dontTouchThatStuff Holding Callbacks Temporarily You can temporarily prevent callback functions from being entered using the aio_hold function This function is not defined in the POSIX standard it is added by the MIPS ABI standard Use it as follows e Call ai
344. ng Asynchronous I O You can initialize asynchronous I O in either of two ways One way is simple the other gives you control over the initialization Implicit Initialization You can initialize asynchronous I O simply by starting an operation with aio_read lio_listio or aio_write The first such call causes default initialization This is the only form of initialization described by the POSIX standard However you may need to control at least the timing of initialization About Synchronous and Asynchronous I O Initializing with aio_sgi_init You can control initialization of asynchronous I O by calling aio_sgi_init refer to the aio_sgi_init 3 reference page and to the declarations in usr include nio h The argument to this call can be a null pointer indicating you want default values or you can pass an aioinit_t structure The principal fields of this structure specify the number of asynchronous processes or threads to execute I O aio_threads The asynchronous I O library creates asynchronous processes or threads to perform the I O It uses sproc in normal programs or pthread_create ina pthread program In either case the default of asynchronous threads is 5 and the minimum is 2 Specify 1 more than the number of I O operations that could reasonably be executed in parallel on the available hardware For example if you will be doing asynchronous I O to one disk file and one tape drive there could be at most tw
345. ng to acquire it for write must wait but multiple readers can own the lock at the same time Preparing Read Write Locks When a thread wants to modify or read data shared by several threads the thread claims the associated lock This can cause the thread to wait until it can acquire the lock When the thread has finished reading or writing the shared data it releases the lock A read write lock has attributes that control its behavior The pthreads library contains several functions used to prepare a lock for use These functions are summarized in Table 13 11 Table 13 11 Functions for Preparing Read Write Locks Function Purpose pthread_rwlockattr_init 3P Initialize a pthread_rwlockattr_t with default attributes pthread_rwlockattr_destroy 3P Uninitialize a pthread_rwlockattr_t pthread_rwlockattr_getpshared 3P Query the process shared attribute pthread_rwlockattr_setpshared 3P Set the process shared attribute pthread_rwlock_init 3P Initialize a rwlock object based on a pthread_rwlockattr_t pthread_rwlock_destroy 3P Uninitialize a read write lock object A read write lock must be initialized before use You can do this in one of three ways e Static assignment of the constant PTHREAD_RWLOCK_INITIALIZER e Calling pthread_rwlock_init passing NULL instead of the address of a read write lock attribute object e Calling pthread_rwlock_init passing a pthread_rwlockattr_t object that you have set up with att
346. nged later see Changing Memory Protection on page 28 flags Options on how the new segment is to be managed The elements of flags determine the way the segment behaves and are as follows MAP_FIXED Take addr literally MAP_PRIVATE Changes to the mapped data are visible only to this process MAP_SHARED Changes to the mapped data are visible to all processes that map the same object 13 Chapter 1 Process Address Space 14 MAP_AUTOGROW _ Extend the object when the process stores beyond its end not a MAP_LOCAL POSIX feature Map is not visible to other processes in share group not POSIX MAP_AUTORESRV Delay reserving swap space until a store is done not POSIX The MAP_FIXED element of flags modifies the meaning of addr Discussion of this is under Choosing a Segment Address on page 21 The MAP_AUTOGROW element of flags specifies what should happen when a process stores data past the current end of the segment provided storing is allowed by prot When flags contains MAP_AUTOGROW the segment is extended with zero filled space Otherwise the initial len value is a permanent limit and an attempt to store more than len bytes from the base address causes a SIGSEGV signal Two elements of flags specify the rules for sharing the segment between two address spaces when the segment is writable MAP_SHARED specifies that changes made to the common pages are visible to other processes sharing the segment This
347. nitiate a program at a specified nondegrading priority explained under Process Scheduling on page 266 using npri You can initiate a program running on a specific CPU of a multiprocessor using runon Both attributes the assigned priority and the assigned CPU are inherited by any child processes that the program creates Process Creation The process that creates another is called the parent process The processes it creates are child processes or siblings The parent and its children together are a share group IRIX provides special services to share groups For example you can send a signal to all processes in a share group The fork function is the traditional UNIX way of creating a process The new process is a duplicate of the parent process running in a duplicate of the parent s address space Both execute the identical program text that is both processes return from the fork call Your code can distinguish them by the return code which is 0 in the child process but in the parent is the new process ID The sproc and sprocsp functions create a lightweight process The difference between these calls is that sproc allocates a new memory segment to serve as the stack for the new process You use sprocsp to specify a stack segment that you have already allocated for example a block of memory that you allocate and lock against paging using mpin The sproc calls take as an argument the address of the func
348. normal IRIX scheduler and it has features designed for real time work including detection of overrun when a scheduled process does not complete its work in the necessary time and underrun when a scheduled process fails to execute in its turn At this writing there are no real time applications that use multiple nodes of an Array system 271 Chapter 13 Thread Level Parallelism IRIX 6 5 conforms to ISO TEC 9945 1 1996 and UNIX 98 that is it supports POSIX threads or pthreads This chapter contains the following main topics Overview of POSIX Threads on page 274 summarizes the similarities and differences of pthreads and processes Compiling and Debugging a Pthread Application on page 275 covers compiling and debugging tools Creating Pthreads on page 277 covers the process of creating a pthread with the desired attributes Executing and Terminating Pthreads on page 280 discusses how threads initialize themselves and how you synchronize on thread termination Using Thread Unique Data on page 283 tells how to define variables that have a unique value in each thread Pthreads and Signals on page 284 discusses the pthread specific details of signal handling see Signals on page 113 for the general information Scheduling Pthreads on page 286 covers scheduling priorities and policies Synchronizing Pthreads on page 288 details the use of mutexes and condition v
349. ns on a Message Queue Operation POSIX Function SVR4 Function Gain access to a queue creating itifit mq_open 3 msegget 2 does not exist Query attributes of a queue and mq_getattr 3 msgctl 2 number of pending messages Change attributes of a queue mq_setattr 3 msgctl 2 Give up access to a queue mq_close 3 n a Remove a queue from the system mq_unlink 3 rm 1 msgctl 2 iperm 1 Overview of Message Queues Table 6 1 Abstract Operations on a Message Queue continued Operation POSIX Function SVR4 Function Send a message to a queue mq_send 3 msgsnd 2 Receive a message from a queue mq_receive 3 msercv 2 Request asynchronous notification ofa maq_notify 3 n a message arriving at a queue Both implementations can be used to communicate between POSIX threads and between IRIX processes in any combination Besides obvious features of syntax the principal differences between the two implementations are as follows POSIX functions are implemented as library functions in the libc library and operate primarily in the user process address space SVR4 functions are implemented in the kernel and every operation requires a context switch This generally results in lower overhead for the POSIX functions The identity of a POSIX or an SVR4 queue is retained over a reboot The contents of a POSIX queue might or might not survive a reboot but you should not depend on either type of queue to retain its state afte
350. ns that operate on semaphores are summarized in Table 4 3 Table 4 3 POSIX Functions to Operate on Semaphores Function Name Purpose and Operation sem_getvalue 3 Return a snapshot of the current value of a semaphore sem_post 3 Perform the V operation incrementing a semaphore and possibly unblocking a waiting process sem_trywait 3 Perform the P operation only if the value of the semaphore is 1 or more sem_wait 3 Perform the P operation decrementing a semaphore and blocking if it becomes negative The abstract operation P is implemented as the sem_wait function Use this to decrement a semaphore s value and if the result is negative to suspend the calling function until the value is restored The V operation is sem_post You can sample a semaphore s value using sem_getvalue The sem_trywait operation is useful when a process or thread cannot tolerate being suspended Using Mutexes and Condition Variables Two additional types of mutual exclusion are available only within a threaded program to coordinate the actions of POSIX threads The mutex is comparable to a lock or to a semaphore initialized to a count of 1 The condition variable provides a convenient way for a thread to give up ownership of a mutex wait for something to happen and then reclaim the mutex Both of these facilities are covered in detail in Chapter 13 Thread Level Parallelism See the headings Mutexes on page 289 and C
351. nstalled bitmap files Refer to the naming conventions for existing bitmap font files see Conventions for Bitmap Font Filenames on page 321 and use names with a consistent format when you create new font names For example Adobe provided Utopia Regular bitmap font files designed for the resolutions of 100 and 75 dpi The original names of these files were UTRG_10 bdf through UTRG_24 bdf Filenames closer to IRIX conventions are utopR10 through utopR24 followed by the appropriate file suffixes Convert files in Bitmap Distribution Format BDF to Portable Compiled Format PCF font files BDF font files are text ASCII files You can think of them as source font files You can put BDF font files into an X font directory but normal practice is to use only binary font formats such as the PCF pcf or compressed PCF format pcf Z for performance reasons Use the bdftopcf command to convert a BDF font file to a PCF font file see the bdftopcf 1 reference page For example Adobe provided two sets of Utopia Regular bitmap font files that were designed for the resolutions of 100 and 75 dpi These files were in the extended Bitmap BDF 2 1 format The original names of the bitmap files were UTRG_10 bdf through UTRG_24 bdf One of them could be converted with the following command bdftopcf o utopR1l0 pcf UTRG_10 bdf However you normally want to compress the PCF file as well You can compress a PCF file by entering a command such as
352. nt level parallel support is based on using common variables in memory and so it can be used only within the bounds of a single memory system a CHALLENGE system or a single node in a POWER CHALLENGEarray system Message Passing Models One way to design a parallel program is to think of each thread of execution as operating in an independent address space communicating with other threads by exchanging discrete units of data as messages through an abstract formal interface for message exchange 251 Chapter 10 Models of Parallel Computation 252 The threads of a program designed in this way can be distributed over different computers Three message passing execution models are supported by Silicon Graphics systems Each defines and implements a formal abstract model for data exchange Two of the models allow a computation to be distributed across the nodes of a multiple memory system without having to reflect the system configuration in the source code The programming models are e Shared Memory Model GHMEM e Message Passing Interface MPI e Parallel Virtual Machine PVM All three models are briefly summarized in the following topics and are discussed in more detail in Chapter 14 Message Passing Parallelism Support for all three is included in the Message Passing Toolkit MPT product For an overview of MPT see this URL http www cray com products software mpt mpt html Shared Memory SHMEM Model The SHME
353. ntrolled files 177 Chapter 7 File and Record Locking Lock Promotion and Demotion A read lock can be promoted to write lock status if no other process is holding a read lock in the same record If processes with pending write locks are waiting for the same record the lock promotion succeeds and the other sleeping processes wait Demoting a write lock to a read lock can be done at any time Because the lockf function does not support read locks lock promotion is not applicable to locks set with that call gt Controlling File Access With File Permissions 178 The access permissions for each UNIX file control which users can read write or execute the file These access permissions may be set only by the owner of the file or by the superuser The permissions of the directory in which the file resides can also affect the access permissions for a file Note that if the permissions for a directory allow anyone to write in the directory and the sticky bit is not included in the permissions files within that directory can be removed even by a user who does not have read write or execute permission for those files If your application warrants the use of record locking make sure that the permissions on your files and directories are also set properly A record lock even a mandatory record lock protects only the records that are locked while they are locked Unlocked parts of the files can be corrupted if proper precauti
354. number of utility functions for setting clearing and testing the bits in a signal mask object Several POSIX signal functions take a signal mask as an argument For example sigsuspend takes a new signal mask and swaps it for the current signal mask establishing which pending signals will be accepted while the process is suspended Using Synchronous Handling You can design your program so that it treats arriving signals as a stream of event records to be processed in sequence For example you could use one or more signal numbers in the POSIX real time range to signify events that are meaningful to your application Your application or one thread in your application can receive each signal in turn and act upon it To implement this design approach follow these steps 1 Block the expected signal numbers in all processes or threads using sigprocmask or pthread_sigmask 2 Send the signals using sigqueue This function permits you to augment the signal number with a union sigval in effect creating an open ended set of sub signals and also assures that multiple signals will be retained until you process them 3 In the signal processing loop wait for the next signal with sigwaitinfo or sigtimedwait When the signal arrives act accordingly and wait again The sigwaitinfo and sigtimedwait functions accept a new signal mask They unblock the specified signal or signals and suspend until one such signal arrives They accep
355. o concurrent I O operations so there is no need to have more than 3 1 more than 2 asynchronous processes the number of locks that the asynchronous I O processes should preallocate aio_locks The default used by aio_init is 3 locks the minimum is 1 Specify the maximum number of simultaneous lio_listio LIO_NOWAIT aio_fsync and aio_suspend calls that your program could execute concurrently If in doubt specify the number of subprocesses your program contains the number of processes or threads that will be sharing the use of asynchronous I O aio_numusers The default is 5 the minimum is 2 Specify 1 more than the number of different processes or pthreads that will be requesting asynchronous I O Other fields of the aioinit_t structure such as aio_num and aio_usedba are not used at this time and must be zero Zero valued fields are taken as a request for the default for that field Example 8 1 shows a subroutine to initialize asynchronous I O given counts of devices and calling processes 199 Chapter 8 Using Asynchronous I O 200 Example 8 1 Initializing Asynchronous I O int initAIO int numDevs int numSprocs int maxOps aioinit_t A 0 ensure zero d fields if numDevs we do know how many devices A aio_threads 1 numDevs if numSprocs we do know how many sprocs A aio_locks A aio_numusers 1 numSprocs if maxOps we do know max aiocbs at 1 time A aio_num maxOps retur
356. o not need to be specifically opened The catalog of choice can be set explicitly once or it can be specified every time a string is needed To specify the default message catalog to be used by subsequent calls to MNLS functions that reference catalogs use setcat include lt pfmt h gt char setcat const char catalog catalog is limited to 14 characters and may contain no character equal to zero or to the ASCII codes for slash or colon See the setcat 3 reference page setcat doesn t check to see if the catalog name is valid it just stores the string for future reference For an example of use see the following topic The catalog indicated by the string must be found in the directory usr lib locale localename LC_MESSAGES Getting Strings From MNLS Message Catalogs MNLS message catalogs do not need to be specifically opened The catalog of choice can be set explicitly once or it can be specified in each reference call Strings are read from a catalog via gettxt see the gettxt 3 reference page include lt unistd h gt char gettxt const char msgid const char defaultStr msgid is a string containing two fields separated by a colon msgfilename msgnumber The msgfilename is a catalog name as described previously in the Specifying MNLS Catalogs on page 377 For example to get message 10 from the MQ catalog you could use either char str gettxt MQ 10 Hello world n or setcat
357. o value to be passed into the callback ay pab gt aio_sigevent sigev_notify SIGEV_CALLBACK pab gt aio_sigevent sigev_func callBack3 pab gt aio_sigevent sigev_value sival_ptr void pch pab gt aio_buf pch gt buffer always the same if DO_SPROCS Wait for the starting gun X barrier convene nprocs endif pch gt etime clock do read and write read and write Set up the aiocb for a read queue it and wait for it EA pab gt aio_fildes pch gt fd pab gt aio_offset pch gt inbase pab gt aio_nbytes BLOCKSIZE if ret aio_read pab ret inWait3 pch if ret break read error 227 Chapter 8 Using Asynchronous I O get the result of the read call the count of bytes read Since aio_error returned 0 the count is nonnegative It could be 0 or less than BLOCKSIZE indicating EOF bytes aio_return pab actual read result if bytes break no need to write a last block of 0 pch gt inbase bytes where to read next time Set up the aiocb for a write queue it and wait for it KY pab gt aio_fildes outFD pab gt aio_nbytes bytes pab gt aio_offset pch gt outbase if ret aio_write pab ret inWait3 pch if ret break pch gt outbase bytes where to write next time while ret amp amp bytes BLOCKSIZE The loop is complete I
358. o_hold AIO_HOLD_CALLBACK to prevent any callback function from being invoked e Call aio_hold AIO_RELEASE_CALLBACK to allow callback functions to be invoked Any that were held are now called e Call aio_hold AIO_ISHELD_CALLBACK returns 1 if callbacks are currently being held otherwise it returns 0 207 Chapter 8 Using Asynchronous I O 208 Multiple Operations to One File When you queue multiple operations to a single file descriptor the asynchronous I O package does not always guarantee the order of their execution There are three ways you can ensure the sequence of operations You can open any output file descriptor passing the flag O_APPEND see the open 1 reference page Asynchronous write requests to a file opened with O_APPEND are executed in the sequence of the calls to aio_write or the sequence they are listed for lio_listio You can use this feature to ensure that a sequence of records is appended to a file in sequence For files that support lseek you can specify any order of operations by specifying the file offset in the aiocb The asynchronous process executes an absolute seek to that offset as part of the operation Even if the operations are not performed in the sequence they were requested the data is transferred in sequence You can use this feature to ensure that multiple requests for sequential disk input are stored in sequential locations For non disk input operations the only way you can b
359. ocation on page 279 Table 13 3 Functions for Creating Pthreads Function Purpose pthread_attr_init 3P Initialize a pthread_attr_t object to default settings pthread_attr_setdetachstate 3P Set the automatic detach attribute pthread_attr_setinheritsched 3P Specify whether scheduling attributes come from the attribute object or are inherited from the creating thread pthread_attr_setschedparam 3P Set the starting thread priority pthread_attr_setschedpolicy 3P Set the scheduling policy pthread_attr_setscope 3P Set the scheduling scope pthread _attr_setstacksize 3P Set the stack size attribute pthread_attr_setguardsize 3P Set the stack guard size attribute pthread_attr_setstackaddr 3P Set the address of memory to use as a stack when you allocate the stack for the new thread 277 Chapter 13 Thread Level Parallelism 278 Table 13 3 Functions for Creating Pthreads continued Function Purpose pthread_attr_destroy 3P Uninitialize a pthread_attr_t object pthread_create 3P Create a new thread based on an attribute object or with default attributes Initial Detach State Detaching means that the pthreads library frees up resources held by the thread after it terminates see Joining and Detaching on page 283 There are three ways to detach a thread e automatically when the thread terminates e explicitly by calling pthread_join e explicitly by calling pthread_detach You can
360. ocation 279 static initializer 281 synchronization of 288 299 termination 282 termination event 281 thread ID 281 thread unique data 283 284 pthread scheduling contention 286 PVM 253 differences from MPI 304 306 R read 195 with guaranteed rate I O 240 reaping child processes 265 resident set size 10 rlimit kernel parameter 6 rpc lockd daemon 192 427 Index S Saudi Arabia country code 418 sched_yield 127 segment 4 heap 4 locking 25 lowest address 4 stack 4 text 4 segment address 21 segments at fixed offsets 21 sem_destroy 83 sem_init 83 semaphore 80 IRIX 87 90 polled 88 POSIX named 84 POSIX unnamed 83 SVR4 96 112 using POSIX 85 setlocal 342 setlocale 340 setrlimit 6 limit 9 sginap 127 shared arena initializing 61 shared memory 53 76 IRIX 61 70 POSIX 55 60 SVR4 71 76 example 73 shared memory See IPC shared memory segment 19 share group 262 SHMEM 252 sigaction 123 428 SIGALRM from interval timer 135 SIGBUS on access to truncated mapped file 18 on NFS error in mapped file 18 on PIO access to invalid bus address 21 on reference past end of mapped segment 13 sigevent structure 198 SIGKILL on reaching limit of virtual swap 8 possible when locking pages 24 signal 113 126 and X intrinsics 120 asynchronous I O use 203 blocking 117 BSD facilities 126 catching 118 com
361. ocation in the node where the program starts up But what if the program contains the CSDOACROSS directive to parallelize the DO loop that processes the array See Chapter 11 Statement Level Parallelism Some number threads say four execute blocks of the DO loop in parallel using four CPUs located in two three or even four different nodes Two problems arise e At least two of the threads have to pay a penalty of at least one router hop to get the data It would be better to allocate parts of the array in the nodes where those threads are running e A single hub chip can easily keep up with the memory demands of two CPUs but when four CPUs are generating constant memory requests one hub may saturate slowing access It would be better to distribute the array data among other nodes any other nodes to prevent a single hub from being a bottleneck Detecting Memory Placement Problems Unfortunately none of the counter values reported by perfex provide a direct diagnosis of bad memory placement You can suspect memory placement problems from a combination of circumstances e Performance does not improve as expected when more parallel threads and CPUs are added e The perfex report shows a relatively low percentage of cache line reuse less than 85 secondary cache hits to pick a common number This is a performance problem you can address for its own sake but it demonstrates that the program depends on a high memory
362. ocks on open files BSD compatible chmod 1 chmod 2 Command and system function that can enable mandatory file locking on a specified file Terminology The discussion of file and record locking depends on the terms defined in this section Record A record is any contiguous sequence of bytes in a file The UNIX operating system does not impose any record structure on files The boundaries of records are defined by the programs that use the files Within a single file a record as defined by one process can overlap partially or completely on a record as defined by some other process Overview of File and Record Locking Read Shared Lock A read lock keeps a record from changing while one or more processes read the data If a process holds a read lock it may assume that no other process can alter that record at the same time A read lock is also a shared lock because more than one process can place a read lock on the same record or on a record that overlaps a read locked record No process however can have a write lock that overlaps a read lock Write Exclusive Lock A write lock is used to gain complete control over a record A write lock is an exclusive lock because when a write lock is in place on a record no other process may read or write lock that record or any data that overlaps it If a process holds a write lock it can assume that no other process will read or write that record at the same time Advisory Lock
363. ode returns the memory data and also sets the bit for the reading CPU to 1 When a CPU discards a cached line for any reason the corresponding bit is set to 0 Thus the directory bits reflect the existence of cached copies of data As long as all CPUs only read the data there is no time cost for directory management Using Origin2000 Nonuniform Memory When a CPU wants to modify a cache line two things happen The hub chip in the node that contains the memory sends a message to every CPU whose directory bit for that line is 1 telling the CPU to discard its copy because it is no longer valid And the modifying CPU is noted as the exclusive owner of that line Any further requests for that line s data are rerouted to the owning CPU so that it can supply the latest version of the data Eventually the owning CPU updates memory and discards the cache line and the directory status returns to its original condition About CC NUMA Performance Issues Most programs operate with good performance when they simply treat the system as having a single large uniform memory When this is not the case IRIX contains tools you can use to exploit the hardware About Default Memory Location Clearly it is a performance advantage for a process to execute on a CPU that is as close as possible to the data used by the process Default IRIX policies ensure this for most programs e Memory is usually allocated on a first touch basis that is it is
364. of your programs need fonts How a program accesses font files depends on the program type e X programs access fonts by calling X font functions such as XListFonts and XLoadFont e IRIS GL and IRIS GL X mixed model programs usually access fonts by calling font management fm functions from the IRIS GL Font Manager library fmenumerate and fmfindfont for example Most fonts are installed when you install the X Window System X11 Execution Environment Some fonts are installed with other software components such as IRIS Showcase Some bitmap fonts are installed when you install a language module such as the Japanese Language Module JLM Some outline fonts are installed when you install a font module such as the Japanese Font Module JFM However most fonts are shared by the X Window System IRIS GL Font Manager Impressario and other software components Using Fonts With the X Window System To maintain compatibility and portability it is best not to access font files directly from an application program because font formats font names font contents and the location of font directories may change Your program should use the Application Programming Interfaces APIs specified for the X Window System and IRIS GL Font Manager or call even higher level functions for the 2D and 3D text available from toolkits such as IRIS Inventor and IRIS Performer Using Fonts With the X Window System This section describes how
365. olling the Degree of Parallelism 258 Choosing the Loop Schedule Type 259 Distributing Data 260 12 Process Level Parallelism 261 Using Multiple Processes 262 Process Creation and Share Groups 262 Process Creation 263 Process Management 264 Process Reaping 265 Process Scheduling 266 Controlling Scheduling With IRIX and BSD Compatible Facilities 266 Controlling Scheduling With POSIX Functions 268 Self Dispatching Processes 269 Parallelism in Real Time Applications 271 13 Thread Level Parallelism 273 Overview of POSIX Threads 274 Compiling and Debugging a Pthread Application 275 Compiling Pthread Source 276 Debugging Pthread Programs 277 Creating Pthreads 277 Initial Detach State 278 Initial Scheduling Scope Priority and Policy 278 Thread Stack Allocation 279 Executing and Terminating Pthreads 280 Getting the Thread ID 281 Initializing Static Data 281 Setting Event Handlers 281 Terminating a Thread 282 Joining and Detaching 283 Using Thread Unique Data 283 XV Contents Pthreads and Signals 284 Setting Signal Masks 285 Setting Signal Actions 285 Receiving Signals Synchronously 286 Scheduling Pthreads 286 Contention Scope 286 Scheduling Policy 287 Scheduling Priority 288 Synchronizing Pthreads 288 Mutexes 289 Preparing Mutex Objects 289 Using Mutexes 292 Condition Variables 292 Preparing Condition Variables 293 Using Condition Variables 294 Read Write Locks 298 Preparing Read Write Locks 298 Using Read Writ
366. ollowing is a sample NLSPATH assignment NLSPATH usr lib locale L LC_MESSAGES 3N usr local 1lib locale L LC_MESSAGES SN usr defaults N Creating XPG 4 Message Catalogs Message catalogs are of this general form these forms are detailed in the gencat 1 reference page Sset n comment a message a n b message b n c message c n Squote d message d Sthis is a comment Each message is identified by a message number and a set Sets are often used to separate messages into more easily usable groups such as error messages help messages directives and so on Alternatively you could use a different set for each source file containing all of that source file s messages Strings and Message Catalogs set n specifies the beginning of set n where n is a set identifier in the range from 1 to NL_SETMAX All messages following the set statement belong to set n until either a delset or another set is reached You can skip set numbers for example you can have a set 3 without having a set 2 but the set numbers that you use must be listed in ascending numerical order and every set must have anumber Any string following the set identifier on the same line is considered a comment delset n deletes the set n from a message catalog quote c specifies a quote character c which can be used to surround message text so that trailing spaces or null empty messages are visible in a message s
367. om the moment a signal is generated until a signal handler begins to execute is the signal latency Signal latency can be long as real time programs measure time and signal latency has a high variability The IRIX kernel normally delivers a pending unblocked signal the next time the process returns to user code from the kernel domain In most cases this occurs e when the process is dispatched after a wait or preemption e upon return from a system function e upon return from the kernel s usual 10 millisecond tick dispatch interrupt SIGALRM which signals the expiration of a real time timer see Timer Facilities on page 127 is given special treatment It is delivered as soon as the kernel is ready to return to a user process after the timer interrupt in order to preserve timer accuracy 119 Chapter 5 Signalling Events 120 When a process is ready to run and is not preempted by a process of higher priority and is executing in user code not calling a system function the latency for other than SIGALRM can be as much as 10 milliseconds However when the process is suspended for example waiting on a semaphore or when there are competing processes having higher priorities the delivery of a signal is delayed until the next time the receiving process is scheduled This can be many milliseconds In general you should use signals to deliver infrequent messages of high priority You should not use the exchange of si
368. ometimes you do not care when threads terminate your program starts a set of threads and they continue until the entire program terminates In other cases threads are created and terminated as the program runs One thread can wait for another to terminated by calling pthread_join specifying the thread ID The function does not return until the specified thread terminates The value the specified thread passed to pthread_exit is returned At this time your program can release any resources that you associate with the thread for example stack space see Thread Stack Allocation on page 279 The pthread_join function also detaches the terminated thread If your program does not use pthread_join you must arrange for terminated threads to be detached in some other way One way is by specifying automatic detachment when the threads are created see Initial Detach State on page 278 Another is to call pthread_detach at any time after creating the thread including after it has terminated If your program creates threads and lets them terminate but does not detach them resources will be used up and eventually an error will occur when trying to create a thread Using Thread Unique Data In some designs especially modules of library code you need to store data that is both e unique to the calling thread e persistent from one function call to another 283 Chapter 13 Thread Level Parallelism Normally the onl
369. on Variables include lt assert h gt include lt pthread h gt typedef int listKey_t typedef struct element_s list element listKey_t key struct element_s next int busyFlag pthread_cond_t notBusy event of no longer in use element_t typedef struct listHead_s list head and mutex pthread_mutex_t mutList right to modify the list element_t head listHead_t Internal function to find an element in a list returning NULL if the key is not in the list A returned element could be in use by another thread busy The caller is assumed to hold the list mutex otherwise the returned value could be made invalid at any time static element_t scanList listHead_t lp listKey_t key element_t ep for ep lp gt head ep ep ep gt next if ep gt key key break return ep Public function to find a key in a list wait until the element is no longer busy mark it busy and return it Ea element_t getFromList listHead_t lp listKey_t key element_t ep pthread_mutex_lock amp lp gt mutList lock list against changes 295 Chapter 13 Thread Level Parallelism 296 while ep scanList lp key amp amp ep gt busyFlag pthread_cond_wait amp ep gt notBusy amp lp gt mutList A if ep ep gt busyFlag 1 pthread_mutex_unlock lp gt mutList return ep Public f
370. on capabilities Refer to the chapter titled Internationalization in the OSF Motif Programmer s Guide for information about the following topics e issues in internationalized applications e compound strings fonts and text display e localizing applications e advanced topics in internationalization There are some important points to remember when you internationalize and localize your application e At the top of your main program issue the call XtSetLanguageProc NULL NULL NULL e Translate your app defaults and install it in usr lib X11 LANG app defaults e Motif uses font sets and font lists to display text Specify a font list in your application defaults file using the following format fontList font list string Be sure to separate elements in the font list string as follows e Separate single fonts with a comma e Separate elements within a font set with a semicolon e End the string with a colon An example of specifying a Japanese fontList is as follows fontList 7x14 mincho 14 14 Translating User Input Translating User Input This section explains the translation of physical user events into programmatic character strings or special keyboard data such as backspace This kind of work should be done by toolkits If you can use a toolkit to manage event processing for you do so and blissfully ignore this section If you are writing a toolkit text object or
371. on is just a string enumerating XLFD names of fonts See X Logical Font Description Conventions an MIT X Consortium standard as well as Font Names on page 313 This string can include wild card characters For example a specification of 16 point fixed fonts might be as follows char fontSetSpecString fixed medium r normal 150 Based on the fonts available a particular server might expand this to a string such as jis fixed medium r normal 16 150 75 75 c 160 Jjisx0208 1983 0 sony fixed medium r normal 16 150 75 75 c 80 1s08859 1 sony fixed medium r normal 16 150 75 75 c 80 jisx0201 1976 0 Internationalization Support in X11R6 Specifying the fontset by simply enumerating the fonts is perfectly acceptable char fontSetSpecString 4is fixed medium r normal 150 75 75 jisx0208 1983 0 sony fixed medium r normal 150 75 75 iso8859 1 sony fixed medium r normal 150 75 75 jisx0201 1976 0 A German locale would work with only the ISO font a Japanese locale might use all three a Chinese locale would have trouble with this fontset The developer should specify a default fontset suitable for the default locale Furthermore developers should ensure that the application accepts localized fontset specifications via resources or message catalogs or command line options Localizers are responsible for providing default fontset specifications suitable for their locales
372. on is taken You specify what that action should be using the sigaction function These actions are set on a process wide basis not individually for each thread Although each thread has a private signal mask signal actions are shared with all threads in the process See Signal Handling Policies on page 118 for details 285 Chapter 13 Thread Level Parallelism Receiving Signals Synchronously You can design a program to receive signals in a synchronous manner instead of asynchronously To do this set a mask that blocks all the signals that are to be received synchronously Then call one of the following three functions sigwait 3 Suspend until one of a specified set of signals is generated then return the signal number sigwaitinfo 3 Like sigwait but returns additional information about the signal sigtimedwait 3 Like sigwaitinfo but also returns after a specified time has elapsed if no signal is received Using these functions you can write a thread that treats signals as a stream of events to be processed This is generally the safest program model much easier to work with than the asynchronous model of signal delivery Scheduling Pthreads 286 The pthreads scheduling algorithm is controlled by three variables a scope policy and priority for each thread These variables are set initially when the thread is created see Initial Scheduling Scope Priority and Policy on page 278 but policy and prio
373. on of the system time CLOCK_REALTIME the hardware cycle counter in this system CLOCK_SGI_CYCLE or the high resolution timer base CLOCK_SGI_FAST The POSIX functions for interval timers are summarized in Table 5 9 Table 5 9 POSIX Time Management Functions Function Name Purpose and Operation alarm 2 timer_create 3C timer_delete 3C timer_settime 3C timer_gettime 3C timer_getoverrun 3C Cause a SIGALRM signal after a specified number of whole seconds Create a POSIX timer and specify its time base CLOCK_REALTIME or CLOCK_SGI_FAST and the signal number it can generate Remove a timer created with timer_create Set expiration and reload times of a timer or disarm it Query the time remaining in a timer Query the number of overrun events generated by a timer Getting Program Execution Time The times function returns counts of accumulated user process and system execution time These counts have a resolution of the system dispatching interval 10 milliseconds Timer Facilities Creating Timestamps The time function returns a timestamp with a resolution of 1 second A timestamp with a resolution this coarse can be used only for infrequent events You can use the clock_gettime function to sample the system time with a resolution of 0 01 second or you can use it to read the hardware cycle counter a free running binary counter with an update frequency near the machine clock rate
374. ondition Variables on page 292 IRIX Facilities for Mutual Exclusion IRIX Facilities for Mutual Exclusion IRIX supports a wide selection of mutual exclusion facilities all tuned for use between processes that run concurrently in a multiprocessor Using IRIX Semaphores Two kinds of semaphores are supported in IRIX IPC normal and polled Both are allocated in a shared memory arena see IRIX Shared Memory Arenas on page 61 Creating Normal Semaphores The functions for managing normal semaphores are summarized in Table 4 4 Table 4 4 IRIX Functions to Manage Nonpolled Semaphores Function Name Purpose and Operation usnewsema 3P Allocate a semaphore in an arena and give it an initial value usfreesema 3P Release arena memory used by a semaphore does not release any process waiting on the semaphore usinitsema 3P Reset a semaphore value and its metering information does not release any process waiting on the semaphore usctlsema 3P Set and reset semaphore metering information and other attributes usdumpsema 3P Dump semaphore metering information to a file To allocate a new shared arena semaphore and set its initial value call usnewsema Use usctlsema to enable recursive use of the semaphore and to enable the collection of metering information You can use the metering information to find out whether a semaphore is a bottleneck or not Tip When reading the reference pages cited above notice that u
375. ons are not taken Only a known set of programs or users should be able to read or write a database This can be enforced through file permissions as follows 1 Using the chown facility see the chown 1 and chown 2 reference pages set the ownership of the critical directories and files to reflect the authorized group ID 2 Using the chmod facility see also the chmod 1 and chmod 2 reference pages set the file permissions of the critical directories and files so that only members of the authorized group have write access 775 permissions 3 Using the chown facility set the accessing program executable files to be owned by the authorized group 4 Using the chmod facility set the set GID bit for each accessing program executable file and to permit execution by anyone 2755 permissions Using Record Locking Users who are not members of the authorized group cannot modify the critical directories and files However when an ordinary user executes one of the accessing programs the program automatically adopts the group ID of its owner The accessing program can create and modify files in the critical directory but other programs started by an ordinary user cannot Using Record Locking This section covers the following topics e Opening a File for Record Locking e Setting a File Lock e Setting and Removing Record Locks e Getting Lock Information e Deadlock Handling Opening
376. ons for Preparing Mutex Objects Function Purpose pthread_mutexattr_init 3P pthread_mutexattr_destroy 3P pthread_mutexattr_getprotocol 3P pthread_mutexattr_setprotocol 3P pthread_mutexattr_getprioceiling 3P pthread_mutexattr_setprioceiling 3P pthread_mutexattr_getpshared 3P pthread_mutexattr_setpshared 3P pthread_mutexattr_gettype 3P pthread_mutexattr_settype 3P pthread_mutex_init 3P pthread_mutex_destroy 3P Initialize a pthread_mutexattr_t with default attributes Uninitialize a pthread_mutexattr_t Query the priority protocol Set the priority protocol choice Query the minimum priority Set the minimum priority Query the process shared attribute Set the process shared attribute Get the mutex type Set the mutex type Initialize a mutex object Uninitialize a mutex object A mutex must be initialized before use You can do this in one of three ways e Static assignment of the constant PTHREAD_MUTEX_INITIALIZER e Calling pthread_mutex_init passing NULL instead of the address of a mutex attribute object e Calling pthread_mutex_init passing a pthread_mutexattr_t object that you have set up with attribute values The first two methods initialize the mutex to default attributes Synchronizing Pthreads Four attributes can be set in a pthread_mutexattr_t You can set the priority inheritance protocol using pthread_mutexattr_setprotocol to one of three values PTHREAD_PR
377. option is not used the program uses O_RDWR with open and PROT_READ PROT_WRITE PROT_AUTOGROW with mmap Wait for keyboard input before exiting allowing you to run other copies of the program while this one has the segment mapped To create a segment named var tmp test seg use a command such as shm_open c x p 0644 s 0x80000 var tmp test seg To attach that segment read only and then wait use the command shm_open r w var tmp test seg From a different terminal window enter the command shm_open var tmp test seg In the original window press lt Enter gt and observe that the value of the first word of the shared segment changed during the wait Example 3 1 POSIX Program to Demonstrate shm_open Program to test shm_open 3 shm_open p lt perms gt s lt bytes gt c x r t w lt path gt p lt perms gt access mode to use when creating default 0600 s lt bytes gt size of segment to map default 64K O use O_CREA x use O_EXCL i use O_RDONLY default is O_RDWR E use O_TRUNC WwW wait for keyboard input before exiting lt path gt the pathname of the queue required zy include lt sys mman h gt shared memory and mmap include lt unistd h gt for getopt include lt errno h gt errno and perror include lt fcntl h gt O_flags include lt stdio h gt int main int argc char argv 06 int perms size_t size 58 00 65536
378. or 64 bit data and 32 bit addressing or 64 for 64 bit addressing The pthreads functions are defined in the library libpthread so Link with this library using the lpthread compiler option which should be the last library on the command line The compiler chooses the correct library based on the execution model usr lib libpthread so usrflib32 libpthread so and usr lib64 libpthread so Note A pthread program is a program that links with libpthread Do not link with libpthread unless you intend to use the pthread interface because libpthread replaces many standard library functions Creating Pthreads Creating Pthreads Debugging Pthread Programs The dbx debugger and Workshop Debugger have been extended for use with threaded programs See the dbx 1M reference page and the documentation for Workshop Debugger for more details You create a pthread by calling pthread_create One argument to this function is a thread attribute object of type pthread_attr_t You pass a null address to request a thread having default attributes or you prepare an attribute object to reflect the features you want the thread to have You can use one attribute object to create many pthreads Functions related to attribute objects and pthread creation are summarized in Table 13 3 and described in the following sections e Initial Detach State on page 278 e Tnitial Scheduling Scope Priority and Policy on page 278 e Thread Stack All
379. or systems where one processor can release the lock while another processor is spinning trying to acquire the lock On a uniprocessor a process waiting to claim a lock is suspended until the lock is released by another process Creating and Managing Locks The functions for creating and controlling locks are summarized in Table 4 7 Table 4 7 IRIX IPC Functions for Managing Locks Function Name Purpose and Operation usnewlock 3P Allocate a lock in a specified arena usfreelock 3P Release lock memory does not release any process waiting on the lock usinitlock 3P Reset a lock and its metering information does not release any process waiting on the lock usctllock 3P Fetch and reset semaphore metering information or debugging information usdumplock 3P Dump lock metering information to a file You decide whether the locks in an arena will have metering information or not You specify this before creating the arena to usconfig see Initializing Arena Attributes on page 61 When lock metering is enabled you can retrieve the information about a lock at any time to find out whether a lock is a bottleneck in a program IRIX Facilities for Mutual Exclusion Claiming and Releasing Locks The functions for using locks are summarized in Table 4 8 Table 4 8 IRIX IPC Functions for Using Locks Function Name Purpose and Operation ussetlock 3P Seize a lock suspending the caller if necessary until the
380. or the starting gun barrier convene nprocs endif pch gt etime clock do read and write read and write 222 Set up the aiocb for a read queue it and wait for it pab gt aio_fildes pch gt fd pab gt aio_offset pch gt inbase pab gt aio_nbytes BLOCKSIZE if ret aio_read pab break ret inWait1 pch If the aio_suspend return is nonzero it means that the wait did not end for i o completion but because of a signal Since we expect no signals here we take that as an error Ad if ret op is complete ret aio_error pab read status should be 0 if ret break signal or nonzero read completion get the result of the read call the count of bytes read Since aio_error returned 0 the count is nonnegative It could be 0 or less than BLOCKSIZE indicating EOF FS bytes aio_return pab actual read result if bytes break no need to write a last block of 0 Asynchronous I O Example pch gt inbase bytes where to read next time Set up the aiocb for a write queue it and wait for it ef pab gt aio_fildes outFD pab gt aio_nbytes bytes pab gt aio_offset pch gt outbase if ret aio_write pab break ret inWait1 pch if ret op is complete ret aio_error pab should be 0 if ret break pch gt outbase
381. or this font enter grep FontName UTRG____ pfa You should get the response FontName Utopia Regular def When this font was added to IRIX the name of the file UTRG____ pfa was changed to Utopia Regular 4 Put the file Utopia Regular in the directory usr lib DPS outline base because that outline font is in the Type 1 format If you have an outline font in the Speedo format put it in the directory usr lib X11 fonts Speedo 326 Installing and Adding Font and Font Metric Files To add the Utopia Regular font and font metric files to the system enter usr bin X11 makepsres o usr lib DPS DPSFonts upr usr lib DPS outline base usr lib DPS AFM You should now be able to access the font file you added For most font families shipped by Silicon Graphics there is one entry per font family in the file usr lib X11 fonts ps2xlfd_map as described in Adding a Bitmap Font The same entry is used for both bitmap and outline fonts If you add your own local bitmap or outline fonts put an entry for each font family in the file called usr lib X11 fonts ps2xlfd_map local You can use entries in the file ps2xlfd_map as templates for entries in the file ps2xlfd_map local If the file ps2xIfd_map local does not exist log in as root and create it You can now access the font you added via the IRIS GL Font Manager To add an outline font in the Type 1 format to the rest of the X Window System in any directory
382. ource is depleted or unready This thread needs to do three things 1 Give up the mutex so that some other thread can renew the shared resource 2 Wait for the event that resource is now ready for use 3 Re claim the mutex for the shared resource These three actions are combined into one action using a condition variable When a thread claims a condition variable it must pass a mutex that it owns The claim releases the mutex waits and reclaims the mutex in one operation Barriers Barriers provide a convenient way of synchronizing parallel processes on multiprocessor systems To understand barriers think of a time when you planned to go to lunch with other people at your workplace The group agrees to meet in the lobby of the building Some of your coworkers reach the lobby early and others arrive later One comes running in last apologizing When all of you have gathered and you know that everyone is ready you all leave the building in a group A barrier is the software equivalent of the lobby where you waited A group of processes are going to work ona problem None should start until all the data has been initialized However starting each process is part of the initialization and they cannot all be started at the same time Each process must be created each must join an arena and perhaps open a file and you cannot predict when they will all be ready To coordinate them you create a barrier Each process when it is read
383. ource line By default there is no quote character and messages are separated by newlines To continue a message onto a second line add a backslash to the end of the first line Sset 1 1 Hello world 2 here is a long string n 3 Hello again n message text n Message 2 in set 1 is here is a long string n Compiling XPG 4 Message Catalogs After creating the message catalog sources you need to compile them into binary form using gencat which has the following syntax gencat catfile msgfile msgfile where catfile is the target message catalog and msgfile is the message source file see the gencat 1 reference page If an old catfile exists gencat attempts to merge new entries with the old gencat resolves set and message number conflicts with new information replacing the old The catfile then needs to be placed in a location where catopen can find it see the XPG 4 Catalog Location on page 374 375 Chapter 16 Internationalizing Your Application 376 SVR4 MNLS Message Catalogs There are many ways to use strings from MNLS message catalogs You can get strings directly and then use them or you can use output routines that search catalogs Putting MNLS Strings Into a Catalog An MNLS catalog source file contains a list of strings separated by new lines For an empty string an empty line is used Strings are referenced by line number in the original source file Applications acce
384. ourier Oblique This font belongs to a font family called Courier which includes e Courier e Courier Bold e Courier Bold Oblique e Courier Oblique When the PostScript page description software language was developed by Adobe Systems the spaces embedded in font names were replaced with dashes PostScript font names look like this Courier Courier Bold Courier BoldoOblique HeiseiMin W3 Adobe Japan1l 2 The size of a font is usually not part of the name of a scalable font because it can be scaled to any size Bitmap fonts are usually designed in specific sizes They are referred to by names such as 12 point Courier or 10 pixel Courier Bold The X Consortium specified 14 part font names for the X Window System Each name is in effect a complete description of the font 313 Chapter 15 Working With Fonts 314 Figure 15 1 shows an example 14 part name for a bitmap font with each part labeled Point sizes in X font names are specified in decipoints tenths of a point Point Vertical Average Foundry Weight Set width size resolution width Encoding adobe courier medium o normal 20 140 100 100 m 110 is08859 1 Font family Slant Pixel Honzontal Spacing Registry size resolution Figure 15 1 X Window System Font Name Example Writing Programs That Need to Use Fonts You can write different types of programs for Silicon Graphics computers for example X IRIS GL OpenGL and mixed model programs Some
385. owing operations p sem Apply the P decrement by 1 operation to sem for example p 1 v sem Apply the V increment by 1 operation to sem for example v 1 Z sem Wait for sem to contain 0 for example z 4 You can give a sequence of operations For example consider the following sequence 1 Wait for zero in semaphore 4 2 Increment semaphore 0 with undo if a following operation fails 3 Decrement semaphore 2 not waiting and with undo 4 Decrement semaphore 3 not waiting and with undo The sequence above can be specified as follows semop k 0x101 z 4 u v 0 n p 2 p 3 The program does not support incrementing or decrementing by other than 1 and there is no way to turn off IPC_NOWAIT or SEM_UNDO once it is on Example 4 6 Program to Demonstrate semop semop program to test semop 2 for all functions semop k lt key gt i lt semid gt n u p lt n gt v lt n gt z lt n gt k lt key gt the key to use or i lt semid gt the semid to use i use the IPC_NOWAIT flag on following ops use the SEM_UNDO flag on following ops p lt n gt do the P operation 1 on semaphore lt n gt v lt n gt do the V operation 1 on semaphore lt n gt z lt n gt wait for lt n gt to become zero 108 IRIX Facilities for Mutual Exclusion KY include lt unistd h gt for getopt include lt sys sem h gt for shmget etc include lt errno h gt
386. p functions take four arguments destp Address of the target memory field you want to update old Expected current value of the memory field new Desired new value based on the expected old value u Address of any IRIX shared memory arena The arena address u is not actually used by the functions However the functions cannot work until usinit has been called at least once Passing an arena address ensures that this has happened 93 Chapter 4 Mutual Exclusion 94 Use a compare and swap function in a loop like the following 1 Copy the current value of the target memory field 2 Calculate a new value based on that current value 3 Use compare and swap to install the new value provided that the current value has not changed during step 2 4 Ifthe compare failed so the swap was not done uscas returns 0 another process has changed the target return to step 1 and repeat The code in Example 4 2 illustrates how this type of loop can be used to manage a simple LIFO queue Example 4 2 Using Compare and Swap on a LIFO Queue include lt ulocks h gt typedef struct item_s struct item_s next other fields ss p item t void push_item item_t lifo item_t new usptr_t u item_t old do new gt next old lifo while 0O uscas lifo ptrdiff_t old ptrdiff_t new u item_t pull_item item_t lifo usptr_t u item_t old new do old lifo if old break
387. patibility 116 handling in pthread 285 handling policy for 118 ignoring 118 latency 119 mask 117 122 mask in pthread 285 multiple received 117 POSIX facilities 120 124 SIGALRM 135 SIGBUS 13 18 21 SIGKILL 8 24 signal numbers 114 116 SIGSEGV 5 10 14 28 SVR4 facilities 124 125 synchronous receipt 119 122 SIGSEGV on access to read only page 28 on attempt to change read only page 10 on reference to undefined page 5 on store past end of mapped segment 14 South Africa country code 418 Spain country code 418 Index Speedo format fonts 319 sproc and mapped segments 15 stack segment 4 6 locking 25 Store Conditional instruction 78 SVR4 and IPC 46 swap 6 9 Sweden country code 418 Switzerland country code 418 synchronous disk output 229 syntax conventions XXXV sysconf 11 syssgi set flush interval 236 system scope threads 286 systune command 7 T Taiwan country code 418 test and set 92 96 compiler intrinsics for 95 instructions 78 library functions for 92 text rendering routines 388 text segment 4 loaded from program file 9 locking 25 read only 10 threads process scope 286 system scope 286 timer 127 136 BSD facilities 134 135 data structures 128 fasthz obsolete 129 hardware cycle counter 135 implementation 129 latency 128 POSIX facilities 129 134 Type 1 font See fonts typographical conventions xxxv typography S
388. pecifying one of three operations Zero meaning to test the semaphore for equality to 0 A positive number such as 1 meaning to increment the semaphore value possibly releasing waiting processes or threads the V operation A negative number such as 1 meaning to decrement the semaphore value when that can be done without making it negative the P operation e A flag word that can specify these flags IPC_NOWAIT do not suspend but return an error if the Zero test fails or the P operation cannot be done SEM_UNDO undo this operation if it succeeds but an operation later in the array should fail In the simplest case you pass an array containing just one operation to increment or decrement one semaphore by 1 the traditional V or P operation Used this way a semaphore in a set is functionally the same as an IRIX or POSIX semaphore SVR4 semaphores permit additional operations not available with IRIX or POSIX semaphores The negative or positive value in the operation structure is not required to be 1 so you can increment or decrement a semaphore by more than 1 in an operation The wait for zero operation allows one process or thread to monitor the state of a semaphore independent of the P and V operations performed on the semaphore by other processes or threads You can also perform a sequence of operations a sequence of P or V or zero wait operations or a mix of operation types on multiple semaphores in a sing
389. ple the delay can be negligible if the data is already in a buffer in memory It can be as long as one rotation time of a disk if the disk is positioned on the correct cylinder It can be longer still if the disk has to seek or if the disk controller or bus adapter is busy with other transfers About Synchronous Output For disk files a process that calls write is normally delayed only as long as it takes to copy the output data to a buffer in the kernel address space The kernel asks the device driver to schedule the device write The actual disk output is asynchronous As a result a process that requests output is usually blocked for only a short time However a number of disk write requests could be pending so the true state of a file on disk is unknown until the file is closed In order to make sure that all data has been written to disk successfully a program calls fsync for a conventional file or msync for a memory mapped file see the fsync 2 and msync 2 reference pages The process that calls these functions is blocked until all buffered data has been written An alternative for disk output is to use direct output discussed under Using Direct I O on page 231 Devices other than disks may block the calling process until the output is complete It is the device driver logic that determines whether a call to write blocks the caller and for how long About Asynchronous I O Some processes should never be blocked
390. port some pragma statements for data placement These are documented in the C Language Reference Manual see Other Useful References on page xxxiv Taking Advantage of First Touch Allocation By default IRIX places memory pages in the nodes where they are first touched that is referenced by a CPU In order to take advantage of this rule you have to be aware of when a first touch can take place With reference to the different means of Address Definition on page 5 e The system call fork duplicates the address space including the placement of all its pages e The system call exec creates initial stack and data pages in the node where the new program will run e The system calls brk and sbrk extend the virtual address space but do not touch new complete pages e The standard and optional library functions malloc when called to allocate more than a page size aligned on a page boundary do not touch any new pages they allocate Space that has been allocated touched and freed can be reused and it stays where it was first touched e The system call mmap does not touch the pages it maps see Mapping Segments of Memory on page 12 e The library call calloc touches the pages it allocates to fill them with zero e The system functions to lock memory pages see Locking and Unlocking Pages in Memory on page 23 do touch the pages they lock It is typical to allocate all memory includ
391. ports no more children exist then it can exit Sometimes it is necessary to handle child termination and other work and the parent cannot suspend In this case the parent can treat the termination of a child process as an asynchronous event and trap it in a signal handler for SIGCLD see Catching Signals on page 118 The wait 2 reference page has extensive discussion of the three methods BSD SVR4 and POSIX for handling this situation with example code for each 265 Chapter 12 Process Level Parallelism 266 Process Scheduling There are two different approaches to setting the scheduling priorities of a process one compatible with IRIX and BSD the other POSIX compliant Controlling Scheduling With IRIX and BSD Compatible Facilities The IRIX compatible and BSD compatible scheduling operations are summarized in Table 12 3 Table 12 3 Commands and Functions for Scheduling Control Function Name Purpose and Operation schedctl 2 Query and set IRIX process scheduling attributes getpriority 2 Return the scheduling priority of a process or share group setpriority 2 Set the priority of a process or process group nice 1 Run a program at a positive or negative increment from normal priority renice 1 Alter the priority of a running process by a positive or negative increment For BSD compatibility use the nice and renice commands to alter priorities and within a program use getpriority and setpriority
392. pport multiple styles for example both Off the Spot and Root Window The application may be able to do in order of preference Over the Spot Off the Spot and Root Window The application should determine that the best match in this case is Off the Spot First discover what the IM can do then set up a variable describing what the application can do as shown in Example 16 8 Example 16 8 Finding What a Client Can Do XIMStyles IMcando XIMStyle clientCanDo note type difference XIMStyl styleWeWillUse NULL XGetImValues im XNQueryInputStyle amp IMcando NULL clientCanDo none XIMPreeditNone XIMStatusNone over XIMPreeditPosition XIMStatusArea off XIMPreeditArea XIMStatusArea root XIMPreeditNothing XIMStatusNothing Translating User Input A client should always be able to handle the case of XIMPreeditNone XIMStatusNone which is likely in a Western locale To the application this is not very different from a RootWindow style but it comes with less overhead Once you know what the application can handle look through the IM styles for a match as shown in Example 16 9 Example 16 9 Setting the Desired IM Style for i 0 i lt IMcando gt count_styles i XIMStyle tmpStyle tmpStyle IMcando gt support_styles i if tmpStyle amp clientCanDo tmpStyle styleWeWillUse tmpStyle if styleWeWillUse NULL exit_with_error XFree IMcando
393. process is blocked the function does not return until the count is nonnegative e When a polled semaphore count remains or becomes negative the function returns 0 and the calling process must use poll to find out when it becomes nonnegative To perform the V operation on a semaphore of either type call usvsema The uscpsema function provides a conditional P operation it performs a P operation on the semaphore only if it can do so without making the value negative The ustestsema function returns the current value of the semaphore which of course is immediately out of date The usinitsema function reinitializes the semaphore to a specified value Note that if you reinitialize a semaphore on which processes are waiting the processes continues to wait You should reinitialize a semaphore only in unusual circumstances 89 Chapter 4 Mutual Exclusion 90 You can call usctlsema to enable the keeping of either metering information cumulative counts of usage or a history trace The metering information shows whether a semaphore is a bottleneck in the program s operations The history trace can be used to analyze bugs Using Locks IRIX locks are implemented differently depending on the hardware architecture of the computer using them On a multiprocessor computer locks are busy wait locks so the processor continually tries to acquire the lock until it succeeds This implementation makes sense only on multiprocess
394. procsp method function to start PR_SALL share all keep FDs sync d void pc argument to child func NULL absolute stack seg CHILD_STACK max stack seg growth QUITIFMONE pc gt procid sproc For each input file call the selected a method as a subroutine to copy its file eA fprintf stderr file s pc gt fname method void pc 0 if errors break fprintf stderr done n SPROCS Wait for all the kiddies to get themselves initialized When all have started and reached barrier all continue If any errors occurred in initialization quit barrier convene nprocs endif Child processes are executing now Reunite the family round the old hearth one last time when their processing is complete Each child ensures that all its output is complete before it invokes barrier l l l barrier convene nprocs Close the output file and print some statistics close outFD 218 clock_t timesum long bytesum double bperus printf procid time fsize filename n for argno 0 timesum bytesum 0 argno lt nfiles argno Asynchronous I O Example pc amp array argno timesum pc gt etime bytesum pc gt fsize printf 2d 8d 8d 8d s n argno pc gt procid pc gt etime pc gt fsize pc gt fname bperus double bytesum double time
395. ptor to a polled semaphore The file descriptor can be passed to poll or select This must be done before the semaphore can be used usclosepollsema 3P Release a file descriptor assigned with usopenpollsema usfreepollsema 3P Release arena memory used by a polled semaphore and invalidate any file descriptors assigned to it IRIX Facilities for Mutual Exclusion Operating on Semaphores The functions for semaphore operations are summarized in Table 4 6 Table 4 6 IRIX IPC Functions for Semaphore Operations Function Name Purpose and Operation uspsema 3P Perform the P operation on either type of semaphore usvsema 3P Perform the V operation on either type of semaphore ustestsema 3P Return the current instantaneous value of a semaphore uscpsema 3P Perform the P operation only if the resulting count will be nonnegative usinitsema 3P Reset a semaphore value and its metering information does not release any process waiting on the semaphore usctlsema 3P Set and reset semaphore metering information and other attributes usdumpsema 3P Dump semaphore metering information to a file To perform the P operation on a semaphore of either type use uspsema When the decremented semaphore value is nonnegative the function returns 1 The action when the decremented count would be negative differs between the polled and normal semaphores e When anormal semaphore count remains or becomes negative the calling
396. quivalence class then both A b and a b are equivalent to Aab Locale Specific Behavior Table 16 7 continued Character Expressions in Internationalized Regular Expressions Expression Description L cc A collating symbol Multi character collating elements must be represented as collating symbols to distinguish them from single character collating elements As an example if the string ch is a valid collating element then ch is treated as an element matching the same string of characters while ch is treated as a simple list of cand h If the string is not a valid collating element in the current collating sequence definition the symbol is treated as an invalid expression c c Any collation element in the character expression range c c where c can identify a collating symbol or an equivalence class If the hyphen character appears immediately after an opening square bracket or immediately prior to a closing square bracket it has no special meaning Within square brackets a period that is not part of a c sequence a colon that is not part of a class sequence and an equals sign that is not part of a c sequence matches itself Table 16 8 shows examples of simple regular expressions Table 16 8 Examples of Internationalized Regular Expressions Pattern Definition a bcd any form of a followed by bcd ch e any element that collates between ch and e
397. r the last program closes it POSIX allows you to set a limit on the number of messages and the size of one message SVR4 allows you to set a limit on the aggregate size of queued messages but not on their number or their individual sizes With a POSIX queue the choice of whether or not operations should block on a full or empty queue is an attribute of the queue descriptor With SVR4 you specify blocking or nonblocking operation on each send or receive operation POSIX supports asynchronous notification of a message arrival SVR4 does not SVR4 allows a receiver to request a message from a particular priority class in effect creating sub queues within a queue POSIX supports a priority class on each message but it always returns the first message of the highest priority class 139 Chapter 6 Message Queues Uses of Message Queues You can use message queues in a variety of ways For example you can use a message queue to implement the producer consumer model of cooperating processes or threads The producer sends its output to the queue the consumer receives the data from the queue When one process gets ahead of the other it is automatically suspended on the queue until the other process catches up Another design model common in real time programming is to use message queues to dispatch units of work to waiting processes or threads A process or thread dedicated to one type of work waits on a message queue
398. ram on a specific node either by node number or with respect to the node where a certain I O device is attached e Distribute the processes of a program among any available cluster of nodes having a specified topology usually cube topology to minimize router distances between nodes e Place specified segments of the virtual address space in designated nodes The dprof profiler see the dprof 1 reference page complements dplace You use dprof to run a program and get a trace report showing which pages are read and written by each process in the program When you have control of the source code of a program you can place explicit calls to dplace within the code The program can call dplace to move specific processes to specific nodes or to migrate specific ranges of addresses to nodes PART TWO Interprocess Communication Chapter 2 Interprocess Communication Provides an overview of the different communication mechanisms and describes the POSIX System V and BSD compatibility features Chapter 3 Sharing Memory Between Processes Describes the different ways of sharing segments of memory between different processes Chapter 4 Mutual Exclusion Describes semaphores locks and other means of synchronization and exclusion between processes and threads Chapter 5 Signalling Events Describes the different interfaces to UNIX signals and the interval timer facilities Chapter 6 Message Queues
399. raphical Conventions xxxv Memory System Calls 11 Functions for Locking Memory 24 Functions for Unlocking Memory 27 Types of IPC and Compatibility 46 SVR4 IPC Name Space Management 50 POSIX Shared Memory Functions 55 IRIX Shared Arena Management Functions 61 Arena Features Set Using usconfig 62 IRIX Shared Memory Arena Allocation Functions 65 IRIX Shared Memory First Datum Functions 66 SVR4 Shared Memory Functions 71 SVR4 Shared Segment Management Operations 72 POSIX Functions to Manage Unnamed Semaphores 83 POSIX Functions to Manage Named Semaphores 84 POSIX Functions to Operate on Semaphores 86 IRIX Functions to Manage Nonpolled Semaphores 87 IRIX IPC Functions for Managing Polled Semaphores 88 IRIX IPC Functions for Semaphore Operations 89 IRIX IPC Functions for Managing Locks 90 IRIX IPC Functions for Using Locks 91 IRIX IPC Functions for Barriers 92 Compiler Intrinsics for Atomic Operations 95 SVR4 Semaphore Management Functions 97 SVR4 Semaphore Set Management Operations 98 SVR4 Semaphore Management Operations 99 Xxix List of Tables XXX Table 5 1 Table 5 2 Table 5 3 Table 5 4 Table 5 5 Table 5 6 Table 5 7 Table 5 8 Table 5 9 Table 5 10 Table 5 11 Table 6 1 Table 6 2 Table 6 3 Table 6 4 Table 6 5 Table 7 1 Table 10 1 Table 11 1 Table 11 2 Table 12 1 Table 12 2 Table 12 3 Table 12 4 Table 13 1 Table 13 2 Table 13 3 Table 13 4 Table 13 5 Table 13 6 Table 13 7 Table 13 8 Table 13 9
400. rated in example programs in this section Managing SVR4 Message Queues The functions used to create and control SVR4 message queues are summarized in Table 6 4 Table 6 4 SVR4 Functions for Managing Message Queues Function Name Purpose and Operation msgget 2 Create a message queue if it does not exist and gain access to it msgctl 2 Query the status of a queue change its owner ID or access permissions or remove it from the system Unlike a POSIX message queue whose name is also a filename the external name of an SVR4 message queue is an integer held in an IPC name table see SVR4 IPC Name Space on page 50 You specify this key when creating the message queue and again whenever you access it for use Creating a Message Queue The msgget function has two purposes It is used to gain access to a queue that exists and it can create a queue that does not exist To create a new queue call msgget with the following arguments key An integer key that is not defined at this time msgflag A set of flags that includes IPC_CREAT and may include IPC_EXCL This value also contains the access permission bits For example a call to create a queue might be written as follows ret msgget PROJ_KEY IPC_CREAT IPC_EXCL 0660 This example relies on a constant PROJ_KEY to supply the key Another option is to use the ftok library function see the ftok 3C reference page 155 Chapter 6 Message Qu
401. re e In order to sample the cycle counter call clock_gettime passing CLOCK_SGI_CYCLE e Jn order to find out the resolution update frequency of the cycle counter call clock_getres passing CLOCK_SGI_CYCLE e Jn order to find out the precision of the cycle counter call syssgi passing SGI_CYCLECNTR_SIZE The returned value is the number of bits in the counter The first two operations are illustrated in Example 5 1 on page 131 Chapter 6 Message Queues You use a message queue to pass blocks of data between processes or threads without having to share any memory between the processes One process or thread puts a message into the queue The message is held in the queue until another process or thread asks for the message IRIX supports two implementations of message queues a POSIX implementation as specified by IEEE standard 1003 1b 1993 and an SVR4 implementation compatible with System V Release 4 Both implementations can be used to coordinate POSIX threads or IRIX processes This chapter discusses message queues under these headings e Overview of Message Queues on page 138 describes message queues and the differences between the two implementations e POSIX Message Queues on page 140 documents the use of the POSIX implementation e System V Message Queues on page 155 documents the use of the SVR4 implementation 137 Chapter 6 Message Queues Overview of Message Queues 138 A me
402. reate a semaphore set or return the ID of a semaphore set semctl 2 Query or change semaphore values query or change semaphore set attributes semop 2 Perform operations on one or more semaphores in a set Semaphores are also discussed in the intro 2 reference page You can display semaphore sets from the command line using ipcs and remove them with ipcrm see the ipcs 1 and ipcr 1 reference pages Creating or Finding a Semaphore Set A process creates a semaphore set or locates an existing set using the semget system function The function creates a set only if the specified key is IPC_PRIVATE or no set with that key exists and the IPC_CREAT flag is used When it creates a set the arguments to the function establish e the numeric key of the set e the number of semaphores in the set from 1 to 25 e the access permissions to the set In addition the effective user ID and group ID of the calling process become the creator and owner identification of the new semaphore set See Example Uses of semget on page 102 for example code 97 Chapter 4 Mutual Exclusion 98 When semget locates an existing set access is controlled by the access permissions of the set and by the user ID and group ID of the calling process The value returned by semget is the ID number of the semaphore set It is used to identify the segment to other functions Managing Semaphore Sets The semctl function gives you the
403. record locking one record is locked which has the size of the entire file The file is locked starting at a byte offset of zero and size of the maximum file size This size is beyond any real end of file so that no other lock can be placed on the file You have a choice of three functions for this operation the basic fentl the library function lockf and the BSD compatible library function flock All three functions can interoperate That is a lock placed by one is respected by the other two Using Record Locking Whole File Lock With fentl The fentl function treats a lock length of 0 as meaning size of file The function lockWholeFile in Example 7 2 attempts a specified number of times to obtain a whole file lock using fentl When the lock is placed it returns 0 otherwise it returns the error code for the failure Example 7 2 Setting a Whole File Lock With fcntl include lt fcntl h gt include lt errno h gt define MAX_TRY 10 int lockWholeFile int fd int tries int limit tries tries MAX_TRY int try struct flock lck lck l_type F_WRLCK write exclusive lock lck l_whence 0 0 offset for l_start Iek start OL lock starts at BOF lck l_len OL extent is entire file for try 0 try lt limit try if 0 fentl fd F_SETLK amp lck break mission accomplished if errno EAGAIN amp amp errno EACC
404. red writes with syssgi as follows syssgi SGI_SSYNC Note This technique is meant for use in a uniprocessor Code executing in an isolated CPU of a multiprocessor is not affected by kernel disk writes unless a large buffer flush monopolizes a needed bus or disk controller Using Guaranteed Rate I O 236 Under specific conditions your program can demand a guaranteed rate of data transfer You would use this feature for example to ensure input of data for a real time video display or to ensure adequate disk bandwidth for high speed telemetry capture About Guaranteed Rate I O Guaranteed rate I O GRIO allows a program to request a specific data bandwidth to or from a filesystem The GRIO subsystem grants the request if that much requested bandwidth is available from the hardware For the duration of the grant the application is assured of being able to move the requested amount of data per second Assurance of this kind is essential to real time data capture and digital media programming GRIO is a feature of the XFS filesystem support EFS the older IRIX file system does not support GRIO In addition the optional subsystem ece sw xfsrt must be installed With IRIX 6 5 GRIO is supported on XLV volumes over disks or RAID systems Using Guaranteed Rate I O GRIO is available only to programs that use direct I O see Using Direct I O on page 231 The concepts of GRIO are covered in sources you should examine
405. redefined events by sending it a message with a user specified tag that the application can check A PVM call is also provided through which a task can kill another PVM task These functions are not available in MPI A task can leave unenroll from a PVM session as many times as it wants whereas an MPI task must initialize finalize exactly once A PVM task need not explicitly enroll the first PVM call enrolls the calling task into a PVM session An MPI task must call MPI_Init before calling any other MPI routine and it must call this routine only once A PVM task can be registered by another task as responsible for adding new PVM hosts or as a PVM resource manager or as responsible for starting new PVM tasks These features are not available in MPI 305 Chapter 14 Message Passing Parallelism 306 e A PVM task can multicast data to a set of tasks As opposed to a broadcast this multicast does not require the participating tasks to be members of a group MPI does not have a routine to do multicasts e PVM tasks can be started in debug mode that is under the control of a debugger of the user s choice This capability is not specified in the MPI standard although it can be provided on top of MPI in some cases e InPVM a user can use the pym_catchout routine to specify collection of task outputs in various ways The MPI standard does not specify any means to do this e PVM includes a receive routine with a timeout capab
406. reduces the memory that is available for all other programs in the system Locking a large program increases the rate of page faults for other programs Locking Program Text and Data Using mpin and mlock you have to calculate the starting address and the length of the segment to be locked It is relatively easy to calculate the starting address and length of global data or of a mapped segment but it can be awkward to learn the starting address and length of program text or of stack space Using mlockall you lock all of the program text and data as it exists at the time of the call You specify a flag either MCL_CURRENT or MCL_FUTURE to give the scope in time One possible way to lock only program text is to call mlockall with MCL_CURRENT early in the initialization of a program The program s text and static data are locked but not any dynamic or mapped pages that may be created subsequently Specific ranges of dynamic or mapped data can be locked with mlock as they are created Locking and Unlocking Pages in Memory Using plock you specify whether to lock text data or both When you specify the text option the function locks all executable text as loaded for the program including shared objects DSOs It does not lock segments created with mmap even when you specify PROT_EXEC to mmap Use mlock or mpin to lock executable mapped segments When you specify the data option plock locks the default data heap
407. regard to their contents as long as the strings remain intact Displaying MB strings on a terminal is done with the usual routines printf puts and so on Many programs such as cat need never concern themselves with the multibyte nature of MB strings since they operate on bytes rather than on characters so MB strings are often used for string I O Manipulation of individual characters in an MB string can be difficult since finding a particular character or position in a string is nontrivial see Handling Multibyte Characters below Therefore it is common to convert to WC strings for that kind of work Handling Multibyte Characters Usually multibyte characters are handled just like char strings Editing such strings however requires some care You cannot tell how many bytes are in a particular character until you look at the character You cannot look at the nth character in a string without looking at all the previous n 1 characters because you cannot tell where a character starts without knowing where the previous character ends Given a byte you don t know its position within a character Thus we say the string has state or is context sensitive that is the interpretation we assign to any given byte depends on where we are in a character This analysis of characters is locale dependent and therefore must be done by routines that understand locale Conversion to Constant Size Characters Multibyte characters
408. ress Space 42 To enable migration for a Fortran or C program using libmp set the LDDSM_MIGRATION environment variable as described in mp 3 In order to enable migration for another type of program run the program under the dplace command with the migration option Using Explicit Memory Placement The dplace execution monitor is a powerful tool that runs any program other than programs that use libmp dplace and libmp manage the same facilities and cannot be used together using a custom memory placement policy that you define using a simple control file The program you run does not have to be recompiled or modified in any way to take advantage of the memory placement and it runs at full speed once started The dplace tool is documented in three reference pages dplace 1 describes the command syntax and options dplace 5 documents the control file syntax and dplace 3 describes how you can call on dplace dynamically from within a program Using dplace you can e Establish the virtual page size of the stack heap and text segments individually at sizes from 16 KB to 16 MB For example if the perfex monitor shows the program is suffering many TLB misses you can increase the size of a data page effectively increasing the span of addresses covered by each TLB entry e Turn on dynamic page migration for the program and set the threshold of local to remote accesses that triggers migration e Place each process within the prog
409. ret gt 0 got a message if quiet if isascii msg gt text 0 printf Sd type ld len d text 32 32s n Cy msg gt type ret msg gt text else printf d type ld len d nonascii n Cc msg gt type ret else an error end loop perror msgrcev break for c lt count good msgget else perror msgget 172 PART THREE Advanced File Control Chapter 7 File and Record Locking Describes the different ways of locking files or records within files for exclusive use between processes and systems Chapter 8 Using Asynchronous I O Describes how to schedule file I O asynchronously in a parallel thread Chapter 9 High Performance File I O Describes the use of direct to disk file I O and guaranteed rate I O Chapter 7 File and Record Locking IRIX supports the ability to place a lock upon an entire file or upon a range of bytes within a file Programs must cooperate in respecting record locks A file lock can be made mandatory but only at a cost in performance For these reasons file and record locking should normally be seen as a synchronization mechanism not a security mechanism The chapter includes these topics Overview of File and Record Locking presents an introduction to locking mechanisms Controlling File Access With File Permissions discusses the relationship of file permissions to exclusive file
410. revious releases of X a string may contain characters from more than one codeset There are several methods for determining which codeset a given character is in which method is appropriate depends on the locale and the encoding used For information on installing and using fontsets with an application refer to Chapter 15 Working With Fonts Such multiple codeset strings usually cannot be rendered using a single font A fontset is a collection of fonts suitable for rendering all codesets represented in a locale s encoding A fontset includes information to indicate which locale it was created in Applications create fontsets for their own use when a program creates a fontset it is told which of the requested fonts are unavailable Example EUC in Japanese To render strings encoded in EUC in Japanese an application would need fonts encoded in 8859 1 JIS X 208 and JIS X 201 The application doesn t need to know which characters in a string go with which font since it doesn t deal with locale specifics So it creates a fontset that is made from a list of user specified fonts under the assumption that the localizer has provided an appropriate list Rendering is then done using that fontset The locale aware rendering system chooses the appropriate fonts for each character being rendered from the supplied list You can find additional information about EUC in Asian Languages Specifying a Fontset A fontset specificati
411. ribute values Synchronizing Pthreads The first two methods initialize the read write lock to default attributes By default only threads within a process share a read write lock Using pthread_rwlockattr_setpshared you can allow any thread from any process with access to the read write lock memory location to claim the read write lock Enable read write lock sharing by changing the default PTHREAD_PROCESS_PRIVATE attribute to PTHREAD_PROCESS_SHARED Using Read Write Locks The functions for claiming releasing and using read write locks are summarized in Table 13 12 Table 13 12 Functions for Using Read Write Locks Function Purpose pthread_rwlock_wrlock 3P Apply a write lock blocking until it is available pthread_rwlock_trywrlock 3P Test a write lock and acquire it if it is available else return an error pthread_rwlock_rdlock 3P Apply a read lock blocking until it is available pthread_rwlock_tryrdlock 3P Test a read lock and acquire it if it is available else return an error pthread_rwlock_unlock 3P Release a read or a write lock To determine where read write locks should be used examine the memory variables and other objects such as files that can be accessed from multiple threads Create a read lock for each set of shared objects that are used together Ensure that the code acquires the write lock before it modifies the shared objects You acquire a write lock by calling pthread_rwlock_wrlock
412. ries 341 Setting the Locale 342 Empty String 342 Nonempty Strings in Calls to setlocale 343 Location of Locale Specific Data 343 Locale Naming Conventions 343 Limitations of the Locale System 345 Multilingual Support 345 Misuse of Locales 345 No Filesystem Information for Encoding Types 346 xviii Contents Character Sets Codesets and Encodings 346 Eight Bit Cleanliness 347 Character Representation 348 Multibyte Characters 349 Use of Multibyte Strings 350 Handling Multibyte Characters 350 Conversion to Constant Size Characters 350 Finding the Number of Bytes in a Character 350 How Many Bytes in an MB String 351 How Many Characters in an MB String 351 Wide Characters 352 Uses for wchar Strings 352 Support Routines for Wide Characters 353 Conversion to MB Characters 353 Reading Input Data 353 Cultural Items 353 Collating Strings 354 Specifying Numbers and Money 355 Using printf 356 Using localeconv 356 Using strfmon 357 Formatting Dates and Times 357 Character Classification and ctype 357 Regular Expressions 359 Locale Specific Behavior 359 Overview of Locale Specific Behavior 360 Local Customs 360 Regular Expressions 360 ANSI X3 159 198X Standard for C 360 Native Language Support and the NLS Database 362 Configuration Data 362 Collating Sequence Tables 363 Character Classification Tables 363 xix Contents Shift Tables 364 Language Information 364 Using Regular Expressions 365 Internationalized Regular
413. ring Tip The mktemp library function can be used to create a unique temporary filename see the mktemp 3C reference page If the specified file doesn t exist usinit creates it and gives it the access permissions specified to usinit with CONF_CHMOD If a shared arena already exists based on that name usinit joins that shared arena If the file exists but is not yet a shared arena usinit overwrites it In any case usinit is subject to normal filesystem permission tests and it returns an error if the process doesn t have read and write permission on the file if it already exists or permission to create the file if it doesn t exist Code to prepare an arena is shown in Example 3 2 Example 3 2 Initializing a Shared Memory Arena usptr_t makeArena size_t initSize int nProcs int ret char tmpname var tmp arenaXXXXXX if ret usconfig CONF_INITUSERS nProcs perror usconfig users return 0 if ret usconfig CONF_INITSIZE initSize perror usconfig size return 0 return usinit mktemp tmpname Joining an Arena Only one process creates a shared arena Other processes join or attach the arena There are three ways of doing this When the arena is not restricted to a single process family either by file permissions or by CONF_ARENATYPE setting any process that calls usinit and passes the same pathname string gains access to the same ar
414. ription of internationalized regular expression grammar in Using Regular Expressions Locale Specific Behavior You can internationalize an application so it can span a range of language and cultural environments This section covers some locale specific topics you should consider when internationalizing an application Topics include e Overview of Locale Specific Behavior e Native Language Support and the NLS Database e Using Regular Expressions e Cultural Data Much of the information in this section is from the X Open Portability Guide For additional information on locale specific behavior refer to the X Open Portability Guide Volume 3 XSI Supplementary Definitions 359 Chapter 16 Internationalizing Your Application 360 Overview of Locale Specific Behavior This section covers e Local Customs e Regular Expressions e ANSI X3 159 198X Standard for C Local Customs To meet the requirements of local customs the X Open Native Language System NLS interface provides a set of library functions that allow cultural data appropriate to the user to be determined at run time Regular Expressions Regular expressions provide pattern matching facilities for text A variety of regular expression support libraries are supplied with IRIX Most of them parse regular expressions in terms of machine collating sequences the English language and the ASCII coded character set
415. riptors or streams User events are discussed in Translating User Input on page 391 It is generally fair to assume that unless otherwise specified data read by an application is encoded suitably for the current locale Text strings typically are in MB format Streams can be read in WC format by using routines defined in widec h This section discusses several aspects of a locale that may differ between locales It includes these topics e Collating Strings describes string collation e Specifying Numbers and Money explains some monetary formats and the printf and localeconv functions e Formatting Dates and Times covers using strftime to format of dates and times e Character Classification and ctype discusses associations between character codes and using macros and functions from usr lib ctype h e Regular Expressions presents information for developers who do their own regular expression parsing and matching 353 Chapter 16 Internationalizing Your Application 354 Also see Cultural Data for additional information Collating Strings Different locales can have different rules governing collation of strings even within identical encodings In English sorting rules are extremely simple each character sorts to exactly one unique place Under ASCII C locale the characters are even in numeric order However neither of those statements is necessarily true for other
416. rity can be modified while the thread is running Contention Scope The scheduling contention scope of a pthread see pthread_attr_setscope 3P determines the set of threads that it competes against for resources System scope threads compete with all other threads on the system and can be created only by privileged users These threads are used in programs when some form of guaranteed that is real time response is required Their scheduling parameters directly affect how the system treats them In addition to the usual scheduling attributes they can select a CPU on which to run using the pthread_setrunon_np call Process scope threads compete within the process and their scheduling attributes are used by the pthread library to select which threads to run on a pool of kernel entities The size of the pool is determined dynamically but may be influenced using the pthread_setconcurrency call Scheduling Pthreads Process scope threads generally require fewer resources than system scope threads because they can share kernel resources The kernel entities themselves share a common set of scheduling attributes which privileged users can change using the process scheduling interfaces see sched_setscheduler 2 and sched_setparam 2 For further details see the pthreads 5 reference page The functions used in scheduling are summarized in Table 13 6 and described in the following sections e Scheduling Policy on page 287 e
417. roblem you re always left with something compiled that can t be localized Resource names therefore use the X Portable Character Set The names may be anything at least they ll mean something to the application author If the names were numbers for example they would be meaningless to everybody Getting X Internationalization Started Xlib s internationalization state like that of libc needs to be initialized Initialization for Toolkit Programming If you re using Xt with a widget set such as IRIS IM Motif or XaW then don t use setlocale Instead use XtSetLanguageProc NULL NULL NULL If you re using a toolkit other than Xt call setlocale as early as possible after execution begins Initialization for Xlib Programming Initialize Xlib s internationalization state after calling setlocale Xlib is being initialized not a server or server specific object so a server connection is not necessary Example 16 5 Initializing Xlib for a Locale if setlocale LC_ALL NULL exit_with_error if XSupportsLocale exit_with_other_error if XSetLocaleModifiers NULL give_warning XSetLocaleModifiers is required only for input Just as passing an empty string to setlocale honors the user s environment so does passing an empty string to XSetLocaleModifiers 385 Chapter 16 Internationalizing Your Application 386 Fontsets In X11R5 and X11R6 unlike p
418. rogram Text and Data on page 24 Processes created with sproc normally share a single address space including mapped segments see the sproc 2 reference page However if flags contains MAP_LOCAL each new process created with sproc receives a private copy of the mapped segment on a copy on write basis When the segment is based on a file or on dev zero see Mapping a Segment of Zeros on page 19 mmap normally defines all the pages in the segment This includes allocating swap space for the pages of a segment based on dev zero However if flags contains MAP_AUTOGROW the pages are not defined until they are accessed see Delayed and Immediate Space Definition on page 7 Note The MAP_LOCAL and MAP_AUTOGROW flag elements are IRIX features that are not portable to POSIX or to System V Mapping a File for I O You can use mmap as a simple low overhead way of reading and writing a disk file Open the file using open but instead of passing the file descriptor to read or write use it to map the file Access the file contents as a memory array The memory accesses are translated into direct calls to the device driver as follows e An attempt to access a mapped page when the page is not resident in memory is translated into a call on the read entry point of the device driver to read that page of data e When the kernel needs to reclaim a page of physical memory occupied by a page of a mapped file and the p
419. roy it afterward Instead you can create a pool containing a small number of processes When a piece of work needs to be done you can dispatch one process to do it The fragmentary code in Example 12 1 shows the general approach Example 12 1 Partial Code to Manage a Pool of Processes typedef void workFunc void arg struct oneSproc struct oneSproc next gt next oneSproc ready to run workFunc calledFunc gt function the sproc is to call void callArg argument to pass to the called func usema_t sprocDone optional sema to post on completion usema_t sprocWait sproc waits for work here sprocList NUMSPROCS usema_t readySprocs count represents sprocs ready to work uslock_t sprocListLock mutex control of sprocList head struct oneSproc sprocList gt first ready oneSproc Put a oneSproc structure on the ready list and sleep on it Called by a child process when its work is done ay void sprocSleep struct oneSproc theSproc ussetlock sprocListLock acquire exclusive rights to sprocList theSproc gt next sprocList put self on the list sprocList theSproc 269 Chapter 12 Process Level Parallelism 270 usunsetlock sprocListLock release sprochist usvsema readySprocs notify master at least 1 on the list uspsema theSproc gt sprocWait sleep until master posts me Body of a general purpos
420. rror semctl IPC_STAT perror semget Example Uses of semctl for Query The program in Example 4 5 semsnap displays a snapshot of the current values of all semaphores in a set you specify The value of each semaphore is displayed in the first row GETVAL followed by the count of processes waiting in a P operation GETNCNT and the count of processes waiting for zero GETZCNT The arguments are as follows k key i id Example 4 5 Numeric key to identify the semaphore set for example k 99 Semaphore ID number alternative to specifying the key Program to Demonstrate semctl for Sampling semsnap program to test semctl 2 for semaphore status commands semsnap k lt key gt i lt semid gt k lt key gt the key to use or i lt semid gt the semid to use include lt unistd h gt for getopt include lt sys sem h gt for shmget etc include lt errno h gt errno and perror include lt stdio h gt int main int argc char argv key_t key int semid 1 LE int nsems j ushort_t semvals 25 ushort_t semns 25 ushort_t semzs 25 struct semid_ds ds 106 key object ID setsize and loop variable snapshot of values snapshot of P waiting snapshot of zero waiting IRIX Facilities for Mutual Exclusion unio int whil if if else n semun arg4 semctl
421. rs unrelated to process scheduling Tip The POSIX scheduling priority values reported by these functions and declared in sched h are not numerically the same as the bands supported by schedctl and declared in sys schedctl h The POSIX numbers are numerically higher for superior priority However the POSIX range is functionally but not numerically equivalent to the normal range supported by schedctl NDPNORMMAX to NDPNORMMIN Using Multiple Processes POSIX scheduling uses one of two scheduling policies strict FIFO and round robin which are described in detail in the sched_setscheduler 2 reference page The round robin scheduler which rotates processes of equal priority on a time slice basis is the default You can query the time slice interval with sched_get_rr_interval You can change both the policy and the priority by using sched_setscheduler Self Dispatching Processes Often each child process has a particular role to play in the application and the function that you name to sproc represents that work The child process stays in that function until it terminates Another design is possible In some applications you may have to manage a flow of many relatively short activities that should be done in parallel However the sproc function has considerable overhead It is inefficient to continually create and destroy child processes You do not want to create a new child process for each small activity and dest
422. running in different address spaces can share data simply by referring to the contents of the shared segment in memory 53 Chapter 3 Sharing Memory Between Processes 54 Shared Memory Based on mmap The basic IRIX system operation for shared memory is the mmap function with which a process makes the contents of a file part of its address space The fundamental uses of mmap are covered under Mapping Segments of Memory on page 12 see also the mmap 2 reference page When two or more processes map the same file into memory with the MAP_SHARED option that single segment is part of both address spaces and the processes can update its contents concurrently The POSIX shared memory facility is a simple formal interface to the use of mmap to share segments The IRIX support for shared arenas is an extension of mmap to make it simpler to create a shared allocation arena and coordinate its use The SVR4 facilities do not directly use mmap but have similar results Sharing Memory Between 32 Bit and 64 Bit Processes Larger Silicon Graphics systems support both 32 bit and 64 bit programs at the same time It is possible for a memory segment to be mapped by programs using 32 bit addresses and simultaneously mapped by programs that use 64 bit addresses There is nothing to prevent such sharing However such sharing can work satisfactorily only when the contents of the shared segment include no addresses at all Pointer valu
423. s When sem_open creates a semaphore it sets the initial value to value or to 0 if value is not specified Otherwise the value depends on the history of the semaphore since it was created The value of a semaphore is not preserved over a reboot the POSIX standard says it is not valid to depend on the value of a semaphore over a reboot A named semaphore is opened as a file and takes up one entry in the file descriptor table for the process There is no way to convert between the address of the sem_t and the file descriptor number or vice versa As a result you cannot directly pass the semaphore to a function such as fentl or chmod Closing and Removing a Named Semaphore When a process stops using a named semaphore it can close the semaphore releasing the associated file descriptor slot This is done with sem_close The semaphore name persists in the filesystem and as long as the system is up the current semaphore value persists in a table in memory To permanently remove a semaphore use sem_unlink Using Semaphores POSIX named and unnamed semaphores can be used to coordinate the actions of IRIX processes and POSIX threads They are the only mutual exclusion objects that can be freely used to coordinate between threaded and unthreaded programs alike Message queues can be used between threaded and unthreaded programs also see Chapter 6 Message Queues 85 Chapter 4 Mutual Exclusion 86 The functio
424. s a name space for IPC objects and the IRIX implementation is free to change its implementation in the future For best portability do not assume that IPC objects are always files If you plan to share an object between processes that could be started from different working directories you should always open the object using the full pathname starting with a slash That ensures that unrelated processes always refer to the same object regardless of their current working directory When a shared object is temporary you can use the tempnam library function to generate a temporary pathname see the tempnam 3 reference page Other POSIX IPC objects nameless semaphores mutexes and condition variables are not persistent but exist only in memory and are identified only by their addresses They disappear when the programs that use them terminate Using IRIX IPC Using IRIX IPC Using System V IPC The IRIX IPC facilities are designed to meet the demands of parallel programming in multiprocessor systems They offer advantages for this use but they are IRIX specific so programs using them are not portable to other systems In order to use any IRIX IPC functions you need to include the correct header files and link libraries when compiling The header files required for each function are listed in the reference pages for the functions IRIX IPC functions are defined in the standard libc library it is included automatica
425. s for signals and file locking are available To use them you must include the correct header files and link libraries when compiling The header files required for each function are listed in the reference pages for the functions One header file signal h declares both SVR4 and BSD signal handling functions Some of the BSD and SVR4 functions have the same names but different types of arguments or different results when called In order to declare the BSD family of signal functions in your program you must be sure to define the compiler variable BSD_SIGNALS or _BSD_COMPAT to the compiler You could do this directly in the source code More often you will manage compilation with make and you will include D_BSD_SIGNALS as one of the compiler options in the Makefile The BSD compatible function for file locking flock is defined in the standard libc library That library is included automatically in any link by the cc command However when you are using C not C the function name flock conflicts with a structure name declared in sys fcntl h In order to define the flock function and not the structure define the compiler variable _BSD_COMPAT A BSD compatible kernel function for managing the termination of child processes wait3 is discussed under Process Reaping on page 265 Chapter 3 Sharing Memory Between Processes There are three families of functions that let you create a segment of memory and sh
426. s to codeset 3 If any other byte whose high bit is 1 appears in the string without being preceded by ss1 or ss2 it is interpreted as all or part of a character from codeset 1 In EUC codeset 1 is always ASCII The other codesets are implementation or user defined This is why EUC cannot support Latin 1 in Asian locales EUC implementations exist but are not standardized for all ideographic Asian languages Unicode The Unicode Consortium has developed a character code system called Unicode Unicode 2 0 covers most of the modern languages scripts CJK Chinese Japanese Korean scripts and scientific and mathematical symbols Each character is represented by a fixed width of 16 bits Unicode 2 0 implements the characters that are coded in the Basic Multilingual Plane of ISO 10646 For more detailed information see Unicode Standard Version 2 0 published by Addison Wesley ISBN 0 201 48345 9 413 Appendix A ISO 3166 Country Names and Abbreviations Table A 1 lists the ISO 3166 country codes alphabetized by country name the table reads from left to right and top to bottom Table A 1 ISO 3166 Country Codes Country Name Code Country Name Code Country Name Code Afghanistan AF Albania AL Algeria DZ American Samoa AS Andorra AD Angola AO Anguilla Al Antarctica AQ Antigua and AG Barbuda Argentina AR Aruba AW Australia AU Austria AT Bahamas BS Bahrain BH Bangladesh BD Barbados BB Belgium BE Belize BZ Benin
427. s write or separate Mutual exclusion Mutexes condition IRIX semaphores and IRIX semaphores and objects variables and locks POSIX locks POSIX read write locks semaphores semaphores POSIX semaphores IRIX semaphores and locks Files pipes and I O Shared single process Shared or separate file Separate file table streams file table table Compiling and Debugging a Pthread Application Table 13 1 Comparison of Pthreads and Processes continued Attribute POSIX Threads Lightweight Processes UNIX Processes Signal masks and Each thread hasa mask Each process has a Each process has a signal handlers but handlers are shared mask and its own mask and its own handlers handlers Resource limits Single process limits Single process limits Limits apply to each process separately Process ID One PID applies to all PID per process plus PID per process threads share group PID It takes relatively little time to create or destroy a pthread as compared to creating a lightweight process Threads share all resources and attributes of a single process except for the signal mask see Pthreads and Signals on page 284 If you want each executing entity to have its own set of file descriptors or if you want to make sure that one entity cannot modify data shared with another entity you must use lightweight processes or normal processes Compiling and Debugging a Pthread Application A pthread application is a C or a C program
428. se I know an architect named Magosa Another example is the specification of Internet messages which calls for 7 bit data Thus if sendmail fails to strip the 8th bit from a character prior to sending it it violates a protocol if it does strip the bit it could garble a non ASCII message this protocol problem is being addressed 347 Chapter 16 Internationalizing Your Application 348 One of the simplest things to do to remove the American bias from a program is to replace the ASCII assumption with the assumption that the Latin 1 codeset will be used This approach is not true internationalization but it can make the application usable in most of Western Europe Latin 1 uses only one byte per character unlike some other codesets so 8 bit clean ASCII software should work without modification using the Latin 1 codeset Ensuring that code is 8 bit clean is the single most important aspect of internationalizing software Another caveat about 8 bit characters applies only to a particular set of circumstances If you are not using a multibyte character type see the next section you should not declare characters as type signed char The default in IRIX C is for char to imply unsigned char If you try to cast a signed char to an int as you must do to use the ctype functions and the character s high bit is set as it may be in an 8 bit character set the high bit is interpreted as a sign bit and extends into the full width of
429. se are used in POSIX time functions and others in BSD based functions and there are somewhat confusing similarities between them Features of these structures are summarized in Table 5 7 Table 5 7 Time Data Structures and Usage Data Type Declared In Contains Some Functions Using This Type time_t time h long int with time in seconds since _ time 2 ctime 3C cftime 3C 00 00 00 UTC January 1 1970 difftime 3C timeval sys time h structure of time_t giving seconds adjtime 2 getitimer 2 and a long int giving microseconds getrusage 3C gettimeofday 3C select 2 utimes 3B itimerval sys time h structure of two timeval fields for getitimer 2 and setitimer 2 first interval and repeat interval timespec_t _ time h structure of time_t giving seconds _ clock_gettime 2 nanosleep 2 and a long int giving nanoseconds aio_suspend 3 sigtimedwait 3C itimerspec time h structure of two timespec_t fields _ timer_settime 3C for first interval and repeat interval timer_gettime 3C tm time h structure of int fields for seconds _ localtime 2 gmtime 2 minutes hours day month etc strftime 3C Time Signal Latency It takes time for the kernel to deliver the SIGALRM that notifies your program at the end of an interval The issue of signal latency in general is discussed under Signal Latency on page 119 The signal latency is less for SIGALRM than for other signals since the kernel initiates a scheduling cycle immediat
430. se fields have different data types and precisions You can use setitimer for any of three operations e With it_value nonzero and it_interval zero initiate a one time interval e With it_value nonzero and it_interval nonzero initiate a repeating timer e With it_value zero disarm the timer preventing it from expiring if it has not expired already Hardware Cycle Counter All current Silicon Graphics systems have a hardware cycle counter a free running binary counter that is incremented at a high regular frequency You can use the cycle counter as a high precision timestamp 135 Chapter 5 Signalling Events 136 The precision of the cycle counter is different in different system types for example it is a 24 bit counter in the Indy workstation but a 64 bit counter in CHALLENGE and Onyx systems The rate at which the timer increments is its resolution and this also varies with the hardware type The cycle counter is an addressable hardware device that you can map into the address space of your process see Mapping Physical Memory on page 20 When this is done you can sample the cycle counter as if it were a program variable The code to do this mapping is discussed in the syssgi 2 reference page under SGI_QUERY_CYCLECNTR However the use of the hardware cycle counter has been integrated into the POSIX timer support beginning in IRIX 6 2 and this makes access to the cycle counter much simpler than befo
431. separate file called the font metric file Character A character is a graphical or mathematical representation of a glyph Letters digits punctuation marks mathematical symbols and cursors are examples of glyphs Font A font is a set of characters that is a set of representations of characters In a bitmap font the shape of each character is represented by a rectangular array of bit values 1 or 0 forming a bitmap of the shape In an outline font the shape of a character is represented by a mathematical description of its outline A distinction exists between a base and composite font A base font is a set of characters of the same size and style Characters in a base font usually match one another in size style weight and slant because their shape size position and spacing have been carefully designed by a skilled font designer A composite font is composed of base fonts with various attributes for example roman and italic or book weight and semibold Font Family or Typeface A professional font designer usually creates an entire font family or typeface composed of a variety of base fonts with related forms rather than a single font A base font family or typeface is a set of base fonts with the same style or design A composite font family or composite typeface is composed of base font families A base font family can consist of bitmap fonts in certain sizes a scalable font that can be used to produce bitmap fonts in
432. sk Once the application has chosen the desired locales it must do one of the following e fork and then call setlocale differently in each process e call setlocale repeatedly as necessary to change from language to language Misuse of Locales The LANG environment variable and the locale variables provide the freedom to configure a locale but they do not protect the user from creating a nonsensical combination of settings For example you are allowed to set LANG to fr French and LC_COLLATE to ja_JP EUC Japanese In such a case string routines would assume text encoded in 8859 1 except for the sorting routines which might assume French text and Japanese sorting rules This would likely result in arbitrary seeming behavior 345 Chapter 16 Internationalizing Your Application No Filesystem Information for Encoding Types The IRIX filesystem does not contain information about what encoding should be associated with any given data Thus applications must assume that data presented to an application in some locale is properly encoded for that locale In other words a file is interpreted differently depending on locale there is no way to ask the file what it thinks its encoding is For example you may have created a file while in a Japanese locale using EUC Later you might try printing it while in a French locale The results will likely resemble a random collection of Latin 1 characters This problem applies to almos
433. snewsema returns the address of a usema_t object and all the other functions take the address of a usema_t That is usema_t represents the type of the semaphore object itself and you refer to a semaphore by its address This is different from locks which are discussed later in this chapter 87 Chapter 4 Mutual Exclusion 88 Creating Polled Semaphores A polled semaphore differs from a normal semaphore in the P operation When decrementing the semaphore value produces a negative number the calling process is not blocked Instead it receives a return code The process then has to include the address of the semaphore in the list of events passed to poll see the poll 2 reference page The V operation applied to a polled semaphore does not release a block process but rather causes a poll operation to end You can use polled semaphores to integrate semaphore handling with other events for which you wait with poll such as file operations You cannot combine the use of normal semaphores with the use of polled devices since a single process cannot wait in a poll call and in a uspsema call at the same time The functions for creating and controlling polled semaphores are summarized in Table 4 5 Table 4 5 IRIX IPC Functions for Managing Polled Semaphores Function Name Purpose and Operation usnewpollsema 3P Allocate a polled semaphore in an arena and give it an initial value usopenpollsema 3P Assign a file descri
434. source the program claims the lock and releases the lock when it is done with the resource The POSIX standard refers to an object of this kind as a mutex a contraction of mutual exclusion that is a conventional term in computer science This book uses the simpler word lock when discussing locks in general and IRIX locks in particular and uses mutex when discussing POSIX mutexes You can use IRIX locks to coordinate between unrelated processes or lightweight processes through an IRIX shared memory arena You can use POSIX mutexes to coordinate between POSIX threads in a threaded program only not IRIX processes You define the meaning of a lock in terms that are relevant to your program s design You decide what resources can be used freely at any time and you decide what resources must be used serially by one process at a time You create and initialize a lock for each serial resource It is also your job to ensure that locks are used consistently in all parts of the program Two errors are easy to make You can forget to claim a lock so that some part of the program uses a resource freely instead of serializing Or you can forget to release a lock so that other processes trying to claim the lock hang or wait forever Both of these errors can be hard to find because the symptoms can be intermittent Most of the time there is no contention for the use of a shared variable For example if one process sometimes
435. sponding outline fonts 325 Chapter 15 Working With Fonts Adding an Outline Font To add the Utopia Regular outline font to the system follow these steps You can install only Adobe text ASCII Type 1 font files or compatibles not binary Type 1 font files and not Type 3 font files The IRIX system can handle Type 3 font files but the X Window System and IRIS GL Font Manager cannot 1 Log in as root 2 Convert the file to Printer Font ASCII PFA format if necessary Printer Font Binary PFB files are not supported To convert pfb files to pfa files use the pfb2pfa command shipped with IRIX version 6 5 see the pfb2pfa 1 reference page For example to convert the Adobe file UTRG____ pfb enter pfb2pfa UTRG pfb UTRG pfa 3 Look at the names of existing outline font files in the directory usr lib DPS outline base The system requires that the name of each outline font file match the PostScript font name specified in the FontName entry in the header of that outline font file For example if you enter grep FontName Courier Bold in the directory usr lib DPS outline base you get FontName Courier Bold def The name revealed is used for the filename of the outline font the filename of the metric file and in the usr lib X11 fonts ps2xlfd map file For example Adobe provided the Utopia Regular outline font file UTRG____ pfa which is an outline font file in the Type 1 format To find the PostScript font name f
436. ss Query the maximum size of the stack segment of the calling process For the parent process this reflects the system limit also available from getrlimit RLIMIT_STACK see getrlimit 2 For a process started by sprocsp the size of the allocated stack Set an upper limit on stack growth for the calling process and for child processes it creates in the future Prevent the calling process from being swapped out This has no connection to paging but to swapping out an entire inactive process under heavy system load The sysmp function gives a privileged process information about and control over the use of a multiprocessor Some of the operations it provides are as follows MP_NPROCS MP_NAPROCS MP_MUSTRUN MP_MUSTRUN_PID MP_GETMUSTRUN Number of CPUs physically in the system Number of CPUs available to the scheduler should be the same as prctl PR_MAXPPROCS Assign the calling process to run on a specific CPU Assign a specified other process typically a just created child process to run on a specific CPU Query the must run assignment of the calling process or MP_GETMUSTRUN_PID of a specified process MP_RUNANYWHERE Allow the calling process or a specified process to run MP_RUNANYWHERE PID on any CPU Using Multiple Processes The runon command see Process Creation on page 263 and runon 1 initiates the parent process of a program running ona specific CPU Any child processes also runs on
437. ss Communication Software products from Silicon Graphics use process level parallelism For example the IRIS Performer graphics library normally creates a separate lightweight process to manage the graphics pipe in parallel with rendering work The run time library for statement level parallelism creates a pool of lightweight processes and dispatches them to execute parts of loop code in parallel see Managing Statement Parallel Execution on page 258 Process Creation and Share Groups The most important system functions you use to create and manage processes are summarized in Table 12 1 Table 12 1 Commands and System Functions for Process Management Function Name npri 1 runon 1 fork 2 pcreate 3C sproc 2 sprocsp 2 pretl 2 sysmp 2 syss i 2 Purpose and Operation Command to run a process at a specified nondegrading priority Command to run a process on a specific CPU Create a new process with a private address space Create a new process with a private address space running a designated program with specified arguments Create a new process in the caller s address space using a private stack Create a new process in the caller s address space using a preallocated stack area Query and set assorted process attributes Query multiprocessor status and assign processes to CPUs Query process virtual and real memory use and other operations Using Multiple Processes You can i
438. ss common case when an arena is shared by unrelated processes each process that calls usinit might be the first one to create the arena or might not If the calling process is the first it should initialize the basic contents and set the shared pointer If it is not the first it should use the initialized contents that another process has already prepared This problem is resolved with uscasinfo as sketched by the code in Example 3 3 Example 3 3 Setting Up an Arena With uscasinfo typedef struct arenaStuff lock _t updateLock exclusive use of this structure short joinedProcs number of processes joined pointers to other things allocated by setUpArena arenaStuff_t The following function performs the one time setup of the arenaStuff contents It assumes that updateLock is held x extern void setUpArena usptr_t arena arenaStuff_t stuff The following function joins a specified arena creating it and initializing it if necessary It could be extended with values to pass to usconfig 3 before the arena is created Ef usptr_t joinArena char arenaPath usptr_t arena arenaStuff_t stuff int ret Join the arena creating it if necessary Exit on error Hip if arena usinit arenaPath perror usinit return arena Do the following as many times as necessary until the arena has been initialized ai for ret 0
439. ss space of a process rlimit_data_max Size of the portion of the address space used for data rlimit_stack_max Size of the portion of the address space used for stack The limits active during a login session can be displayed and changed using the C shell command limits A program can query the limits with getrlimit and change them with setrlimit see the getrlimit 2 reference page Defining the Address Space The initial default value and the possible range of a resource limit is established in the kernel tuning parameters For a quick look at the kernel limits use fgrep rlimit var sysgen mtune kernel To examine and change the limits use systune see the systune 1 reference page Example 1 1 Using systune to Check Address Space Limits systune i Updates will be made to running system and unix install systune gt rlimit_vmem_max rlimit_vmem_max 536870912 0x20000000 11 systune gt resource group resource statically changeable 536870912 0x20000000 11 536870912 0x20000000 11 rlimit_vmem_max rlimit_vmem_cur 536870912 0x20000000 11 67108864 0x4000000 11 rlimit_stack_max rlimit_stack_cur Tip These limits interact in the following way each time your program creates a process with sproc and does not supply a stack area see the sproc 2 reference page an address segment equal to rlimit_stack_max is dedicated to the stack of the new process When rlimit_stack_max is set high a program that
440. ss the catalog by line number so it s very important not to change the line numbers of existing catalog entries This means that when you want to add a new string to an existing catalog source you should always append it to the end of the file if you put it in the middle of the file then you change the line number for subsequent strings The following tools can help you compile MNLS message catalogs exstr 1 Searches a C source file for literal strings and lists them or replaces them with MNLS function calls mkmsgs 1 Creates a message catalog for a particular locale converting source text lines to the form used by exstr srchtxt 1 Displays selected strings from a message catalog When a file of strings is ready to be compiled simply run mkmsgs and put the results in the directory usr libflocaleflocalename LC_MESSAGES Using MNLS in Shell Scripts One difference between MNLS and XPG 4 catalog functions is that the MNLS catalog can be used from commands and hence it can be used to internationalize a shell script The following table summarizes MNLS functions that have both a command line and a function library version gettxt 1 Retrieve a string from the catalog Ifmt 1 Retrieve a format string insert arguments display to stderr and to system log or textport pfmt 1 Retrieve a format string insert arguments display to stderr Strings and Message Catalogs Specifying MNLS Catalogs MNLS message catalogs d
441. ssage queue is a software object maintained by the IRIX kernel logically apart from the address space of any process When you create a message queue the queue has a public identifier The identifier is a file pathname for POSIX or an integer for SVR4 A process uses the identifier to open the queue When the queue is open the process can send messages to the queue or receive messages from the queue A message queue has an access mode similar to a file access mode specifying read and write access for its owner its owner s group or all users A process with an effective user ID giving only read access can only receive messages from the queue A process with an effective user ID lacking access cannot open the queue When a process requests a message from a queue and no message is available the process can be notified immediately with an error code or it can be suspended until a message is sent A message queue has a limit on the amount of data that can be queued POSIX limits the number of messages SVR4 limits the total size of queued messages When a process sends a message that would exceed the queue s limit the process can be notified immediately with an error code or it can be suspended until there is room in the queue Implementation Differences The abstract operations that a message queue supports are summarized in Table 6 1 with the names of the POSIX and SVR4 functions that implement them Table 6 1 Abstract Operatio
442. ssor These functions are detailed in the test_and_set 3 and uscas 3 reference pages In addition the MIPSpro C and C compilers version 7 0 and after contain built in support for these operations IRIX Facilities for Mutual Exclusion Using Test and Set All test and set functions solve a similar problem how to update the contents of a memory word reliably from two or more CPUs concurrently Use a test and set function to avoid the traditional race condition For example suppose that two or more processes could execute code to increment a variable as in the C expression shared e Process A loads shared into a register and adds 1 to it e Process B loads shared into a register and adds 1 to it e Process A stores the value in memory e Process B stores the value in memory The result is to increment shared by 1 when it should be incremented by 2 However if both processes use test_then_add amp shared 1 instead they are assured that both increments will occur regardless of timing Using Compare and Swap The test and set functions are not adequate to do race free pointer manipulation you need a compare and swap function for that The C library includes the uscas and uscas32 functions for this purpose Use uscas to work with pointer sized values which can be either 32 or 64 bits depending on compile options Use uscas32 to work with words that should always be 32 bits in every program The compare and swa
443. st on the first vowel of the word then by consonants which may precede or follow the vowel in question Cultural Items e Primary Secondary sorts consider some characters as equals until there is a tie For example in French a 4 a and 4 all sort to the same primary location If two strings such as tache and tache collate to the same primary order then the secondary sort distinguishes them e Special case sorts exist for some Asian languages For example Japanese kanji has no strict sorting rules Kanji strings can be sorted by the strokes that make up the characters by the kana phonetic spellings of the characters or by other agreed upon rules It should be clear that a programmer cannot hope to collate strings by simple arithmetic or by traditional methods Locale specific collation should be performed with strcoll and strxfrm These are table driven functions the tables are supplied as part of locale support The value of LC_COLLATE determines which ordering table to use See the strcoll 3 and strxfrm 3 reference pages strcoll has the same interface as stremp and can be directly substituted into code that uses stremp However strcoll can consume more CPU time so where it is used in a time critical loop you may have to redesign Specifying Numbers and Money Format of simple numbers differs from locale to locale Characters used for decimal radix and group separators vary Grouping rules may
444. statement that starts with oe Put this statement at the beginning of your PS file If you have two such lines delete the second one When you download a font this way the font is available only while your print job is being processed e You can make a copy of a Type 1 font file and then insert the statement serverdict begin 0 exitserver after the first group of comment statements lines that start with if no password has been specified for your printer otherwise replace 0 in the above statement with the password for your printer Then send the edited file to your printer When you download a font this way the warning message S exitserver permanent state may be changed is sent to the file usr spool Ip log on the system to which the printer is attached The permanent state of the printer is not really changed Downloaded fonts disappear when you reset the printer by switching its power off and on If there is not enough memory for additional fonts you receive a message about a Virtual Memory VM error and the font is not downloaded If you again send the program that produces a list of available fonts to your printer you should see the PostScript names of the fonts you downloaded on that list 330 PART SIX Internationalizing Your Application Chapter 16 Internationalizing Your Application Documents how to prepare an application to execute in more than one language environment includin
445. sted in Table 15 1 Table 15 1 Font and Font Metric Directories Directory Path Conventional Contents usr lib DPS outline base Outline font files in the Adobe Type 1 format usr lib X11 fonts Typel Symbolic links to font files in usr lib DPS outline base usr lib DPS AFM Adobe Font Metric AFM files usr lib X11 fonts 100dpi Bitmap fonts designed for the screen resolution of 100 dpi usr lib X11 fonts 75dpi Bitmap fonts designed for the screen resolution of 75 dpi usr lib X11 fonts misc Miscellaneous other bitmap fonts usr lib X11 fonts Speedo Outline font files in the Bitstream Speedo format usr lib X11 fonts CID AFM CCM CFM CIDFont and CMap files for large outline fonts in the Adobe CID keyed format usr share ghostscript fonts Ghostscript fonts accessible only to Ghostscript but not to the rest of the X11 system Any font format known to Ghostscript could be in this location 319 Chapter 15 Working With Fonts 320 The X Window System IRIS GL Font Manager Impressario and other software components use the directories listed in Table 15 1 by default The locations of font files are made known to the X Window System in two ways e Within each directory specified in the X font path a file named fonts dir contains a directory of filenames with their corresponding 14 part font names For example to see the font names available in usr lib X11 fonts 100dpi use the command more usr lib X11 fonts 100dpi fonts
446. sum printf total time d usec total bytes d g bytes usec n timesum bytesum bperus Unlink the arena file so it won t exist when this progam runs again If it did exist it would be used as the initial state of the arena which might or might not have any effect z unlink arenaPath return 0 inProcO alternates polling with aio_error with sginap Under the Frame Scheduler it would use frs_yield instead of sginap The general pattern of this function is repeated in the other three only the wait method varies from function to function BRK KK KK KR RR RR RR RRR RR RR RR RA A AA A A A A A A A A A I A He int inWait0O child_t pch int ret aiocb_t pab amp pch gt ach while EINPROGRESS ret aio_error pab sginap 0 return ret void inProc0O void arg size_t stk child_t pch arg starting arg is gt child_t for my file aiocb_t pab amp pch gt ach base address of the aiocb_t in child_t int ret as long as this is 0 all is ok int bytes bytes read on each input Initialize no signals or callbacks needed Chapter 8 Using Asynchronous I O Kel pab gt aio_sigevent sigev_notify SIGEV_NONE pab gt aio_buf pch gt buffer always the same if DO_SPROCS Wait for the starting gun EJ barrier convene npro
447. t They run on a limited number or even just one CPU when necessary For example the Fortran programmer can control the number of CPUs used by a MIPSpro Fortran 77 program by setting environment variables before the program starts see Chapter 11 Statement Level Parallelism Types of Memory Systems The key memory issue for parallel execution is this Can one process access data in memory that belongs to another concurrent process and if so what is the time penalty for doing so The answer depends on the hardware architecture and determines the optimal programming model Single Memory Systems The CHALLENGE Onyx system architecture uses a high speed system bus to connect all components of the system One component is the physical memory system which plugs into the bus and is equally available to all other components Other units that plug into the system bus are I O adapters such as the VME bus adapter CPU modules containing MIPS R4000 R8000 or R10000 CPUs are also plugged into the system bus 245 Chapter 10 Models of Parallel Computation 246 In the CHALLENGE Onyx architecture the single common memory has these features e There is a single address map that is the same word of memory has the same address in every CPU e There is no time penalty for communication between processes because every memory word is accessible in the same amount of time from any CPU e All peripherals are equally accessible fro
448. t all stored strings Most strings are uninterpreted sequences of nonzero bytes This includes for example filenames You can if you want to name your files using Chinese characters in a Chinese locale but the names will look odd to anyone who runs bin ls on the same filesystem using a non Chinese locale Character Sets Codesets and Encodings 346 One major difference between nationalized and internationalized software is the availability in internationalized software of a wide variety of methods for encoding characters Developers of internationalized software no longer have the convenience of always being able to assume ASCII Three terms that describe groupings of characters are the following character set An abstract collection of characters codeset A character set with exactly one associated numerical encoding for each character The English alphabet is a character set ASCII is a codeset encoding A set of characters and associated numbers however this term is more general than codeset A single encoding may include multiple codesets Extended UNIX Code EUC for instance is an encoding that provides for four codesets in one data stream Character Sets Codesets and Encodings This section describes these topics Eight Bit Cleanliness explains how to make 8 bit clean characters e Character Representation discuses multibyte and wide characters e Multibyte Characters covers using and handl
449. t be given shmid shmget key 0 0 if 1 shmid we have an ID attach shmat shmid addr rwflag if attach void 1 printf Attached at Ox lx first word Ox 1lx n attach pid_t attach if rwflag SHM_RDONLY pid_t attach getpid printf Set first word to 0x 1lx n pid_t attach if wait char inp 80 printf Press return to detach gets inp printf First word is now 0x 1lx n pid_t attach if shmdt attach perror shmdt else perror shmat else perror shmget return errno Chapter 4 Mutual Exclusion You use mutual exclusion facilities whenever data is shared by multiple independent processes or threads Using such objects as locks also called mutexes and semaphores you can Ensure that only one process or thread uses a particular data structure at any time Synchronize activities so that processes or threads can wait for the completion of events or actions by other processes or threads Coordinate the use of a shared collection such as a ring buffer or queue In order to share data between processes you share memory between them Memory sharing is covered in Chapter 3 Sharing Memory Between Processes When independent processes share access to data in disk files they can ensure mutual exclusion using file locks which are covered in Chapter 7 File and Record Locking
450. t that signal restore the original signal mask and return the signal information You could construct a very similar work handling application using a message queue see Chapter 6 Message Queues However this design approach allows you to integrate the handling of unplanned signals such as SIGPIPE and interval timer signals such as SIGALRM into the same scheme as planned application events Signals Using Asynchronous Handling Using sigaction you specify a function to be called when a particular signal is received You have a choice of function prototypes In each case the signal handler is passed the signal number additional information about the signal and information about the machine context at the time the signal was delivered Your signal handler can have the POSIX prototype as follows void name int sig siginfo_t sip ucontext_t up The second argument a POSIX information structure siginfo_t contains these fields si_signo The signal number again si_errno Either 0 or an error code from errno h si_code An indication of the source of the signal si_value When si_code is SI_QUEUE the union sigval passed to sigqueue si_pid When si_code is SI_LUSER the process ID that called kill When the signal is an error reported by the kernel or hardware si_code is an explanatory number These values are spelled out in detail in the siginfo 5 reference page The third argument a pointer to a ucontext_t ob
451. t to specify the start or length of a record e The LOCK_NB flag requests the function to return if the lock cannot be placed Without this flag the function suspends until the lock can be placed Setting and Removing Record Locks Locking a record is done the same way as locking a file except that the record does not encompass the entire file contents This section examines an example problem of dealing with two records which may be either in the same file or in different files that must be updated simultaneously so that other processes get a consistent view of the information they contain This type of problem occurs for example when updating the inter record pointers in a doubly linked list 183 Chapter 7 File and Record Locking 184 To deal with multiple locks consider the following questions e What do you want to lock e For multiple locks in what order do you want to lock and unlock the records e What do you do if you succeed in getting all the required locks e What do you do if you fail to get one or more locks In managing record locks you must plan a failure strategy for the case in which you cannot obtain all the required locks It is because of contention for these records that you have decided to use record locking in the first place Different programs might e wait a certain amount of time and try again e end the procedure and warn the user e let the process sleep until signaled that the lock has been fr
452. te key and thus creates a message queue that can be used from this program only This is not useful since the program does nothing with the queue before it terminates System V Message Queues Example 6 5 Program to Demonstrate msgget Program to test msgget 2 l msgget k lt key gt p lt perms gt x c k lt key gt the key to use default 0 IPC_PRIVATE p lt perms gt permissions to use default 600 l x use IPC_EXCL g use IPC_CREAT include lt sys msg h gt msg queue stuff ipc h types h include lt unistd h gt for getopt include lt errno h gt errno and perror include lt stdio h gt int main int argc char argv key_t key IPC_PRIVATI int perms 0600 int msgflg 0 int msqid Fl 7 key permissions flags CREAT EXCL returned msg queue id struct msqid_ds buf buffer for stat info int e while 1 c getopt argc argv k p xc switch c case k key key key_t strtoul optarg NULL 0 break case p permissions perms int strtoul optarg NULL 0 break case c msgflg IPC_CREAT break case x msgflg IPC_EXCL break default unknown or missing argument return 1 msqid msgget key msgflg perms if 1 msqid 161 Chapter 6 Message Queues print
453. tem MPI messages are passed over a HIPPI network Latency and bandwidth are intermediate between memory to memory data exchange and socket based network communication Parallel Virtual Machine PVM Model PVM is an integrated set of software tools and libraries that emulates a general purpose flexible heterogeneous concurrent computing framework on interconnected computers of varied architecture Using PVM you can create a parallel application that executes as a set of concurrent processes on a set of computers that can include uniprocessors multiprocessors and nodes of Array systems Like MPI PVM has wide use on many types of supercomputer including Cray systems An implementation of PVM is included in the MPT PVM is discussed in more detail under Chapter 14 Message Passing Parallelism 253 Chapter 11 Statement Level Parallelism You can use statement level parallelism in three language packages Fortran 77 Fortran 90 and C This execution model is unique in that you begin with a normal serial program and you can always return the program to serial execution by recompiling Every other parallel model requires you to plan and write a parallel program from the start 255 Chapter 11 Statement Level Parallelism Products for Statement Level Parallelism 256 Software support for statement level parallelism is available from Silicon Graphics and from independent vendors Silicon Graphics Support T
454. tesi nuucp 234964 Jun 4 10 17 incatl rwxr xr x 1 cortesi nuucp 234964 Jun 4 10 17 incat2 rwxr xr x 1 cortesi nuucp 234964 Jun 4 10 18 incat3 rwxr Xr xX 1 cortesi nuucp 234964 Jun 4 10 19 incat4 gt aiocat o outcat a 0 incat procid time fsize filename 0 920 440000 234964 incatl 1 939 480000 234964 incat2 2 940 510000 234964 incat3 3 936 530000 234964 incat4 total time 1960000 usec total bytes 939856 0 479518 bytes usec gt aiocat o outcat a 1 incat procid time fsize filename 209 Chapter 8 Using Asynchronous I O 210 NFO 3 total time 1460000 usec gt aiocat o outcat a 2 incat Nr Oo By total time 350000 usec gt aiocat o outcat a 3 incat 0 Ts 2 3 o 942 944 949 946 procid 962 955 967 960 procid 909 969 966 972 350000 370000 370000 370000 time 90000 80000 90000 90000 time 50000 50000 60000 60000 234964 234964 234964 234964 fsize 234964 234964 234964 234964 fsize 234964 234964 234964 234964 incatl incat2 incat3 incat4 total bytes 939856 filename incatl incat2 incat3 incat4 total bytes 939856 filename incatl incat2 incat3 incat4 0 643737 bytes usec 2 6853 bytes usec total time 220000 usec total bytes 939856 4 27207 bytes usec Asynchronous I O Example Example 8 4 Source Code of aiocat aiocat c This highly artificial example demonstrates asynchronous I O The comma
455. that CPU unless the parent reassigns them to run anywhere or to run on a different CPU using sysmp The use of restricted CPUs and assigned CPUs to get predictable real time performance is discussed at length in the REACT Real Time Programmer s Guide The syssgi function has a number of interesting uses but only one of interest for managing processes syssgi SGI_PROCSZ returns the virtual and resident memory occupancy of the calling process Process Reaping A parent process should not terminate while its child processes continue to run When it does so the parent process of each child becomes 1 the init process This causes problems if a child process should loop or hang The functions you use to collect the technical term is to reap the status of child processes are summarized in Table 12 2 Table 12 2 Functions for Child Process Management Function Name Purpose and Operation wait 2 Function to block until a child stops or terminates and to receive the cause of its change of status waitpid 2 POSIX extension of wait which allows more selectivity and returns more information wait3 2 BSD extension of wait that allows you to poll for terminated children without suspending waitid 2 Function to suspend until one of a selected set of status changes occurs in one or more child processes When the parent process has nothing to do after starting the child processes it can loop on wait until wait re
456. that uses some of the POSIX pthreads functions In order to use these functions and in order to access the thread safe versions of the standard I O macros you must include the proper header files and link with the pthreads library You can debug and analyze the compiled program using some of the tools available for IRIX 275 Chapter 13 Thread Level Parallelism 276 Compiling Pthread Source The header files related to pthreads functions are summarized in Table 13 2 Table 13 2 Header Files Related to Pthreads Header Primary Contents errno h System error codes returned by pthreads functions pthread h Pthread functions and special pthread data types sched h The sched_param structure and related functions used in setting thread priorities stdio h Standard stream I O macros including thread safe versions sys types h IRIX and standard data types limits h Some POSIX constants such as _POSIX_THREAD_THREADS_MAX unistd h Constants used when calling sysconf to query POSIX limits see the sysconf 3 reference page It is recommended that the thread safe options be enabled at compile time using the feature test macro _POSIX_C_SOURCE see intro 3 for details For example to compile these options use this command cc D_POSIX_C_SOURCE 199506L app c llib0 1libl lpthread You can use pthreads with a program compiled to any of the supported execution models 32 for compatibility with older systems n32 f
457. the differences between PostScript and X Windows font names e Writing Programs That Need to Use Fonts covers X programs and IRIS GL and IRIS GL X programs Terminology Before discussing how to use fonts consider these terms Typography Typography is the art and technique of working with type In traditional typography the term type refers to a piece of wood or metal with a raised image of a character or characters on its upper face Such pieces of wood or metal are assembled into lines and pages which are printed by a letterpress process What typographers do with type is called typesetting or composition Type can also refer to the images produced by using such pieces of wood or metal Font Basics Traditional typesetting is seldom used today In modern typography type usually refers to the images produced on typesetting or composition systems which do not use wooden or metal type such as photo and digital composition systems The typography on a digital system such as a digital computer is called digital typography Digital typography is based on a hierarchy of objects called characters fonts and font families or typefaces Numeric values or measurements related to those objects can be divided into character metrics font metrics and typeface metrics Sometimes all information about a font family or typeface is stored in a set of font files but sometimes metric information for a set of font files is stored in a
458. the memory system with the system calls shown in Table 1 1 Table 1 1 Memory System Calls Memory Information System Call Invocation Size of a page in a data segment uiPageSize getpagesize uiPageSize sysconf _SC_PAGESIZE Virtual and resident sizes of a process syssgi SGI_PROCSZ pid amp uiSZ amp uiRSS Maximum stack size of a process uiStackSize prctl PR_GETSTACKSIZE Free swap space in 512 byte units swapctl SC_GETFREESWAP amp uiBlocks Total physical swap space in512 byte swapctl SC_GETSWAPTOT amp uiBlocks units Total real memory sysmp MP_KERNADDR MPSA_RMINFO amp rmstruct Free real memory sysmp MP_KERNADDR MPSA_RMINFO amp rmstruct Total real memory swap space sysmp MP_KERNADDR MPSA_RMINFO amp rmstruct The structure used with the sysmp call shown above has this form a more detailed layout is in sys sysmp h struct rminfo __uint32_t freemem pages of free memory __uint32_t availsmem total real swap memory space __uint32_t availrmem available real memory space __uint32_t bufmem not useful __uint32_t physmem total real memory space 11 Chapter 1 Process Address Space Mapping Segments of Memory Your process can create new segments within the address space Such a mapped segment can represent e the contents of a file e asegment initialized to binary zero e a POSIX shared memory object e a view of the kernel s private addr
459. tion Avoid arithmetic on character values Use the macros in ctype h to get information about a given character These macros are table driven and locale sensitive If you prefer you can use the functions that correspond to these macros instead Character Classification and ctype on page 357 provides more detailed information on these macros and functions If you do your own regular expression parsing and matching use the XPG 4 extensions to traditional regular expression syntax for internationalized software See Regular Expressions on page 359 for more information Where possible use the XPG 4 rather than the MNLS interface in order to maximize portability See Strings and Message Catalogs on page 372 for more information Provide a catalog for your locale See SVR4 MNLS Message Catalogs on page 376 for more information The File Typing Rule FTR strings that are used to customize the IRIX Interactive desktop can be Internationalized See Internationalizing File Typing Rule Strings With MNLS on page 380 for more information Use message catalogs for printf format strings that take linguistic parameters and allow localizers to localize the format strings as well as text strings See Variably Ordered Referencing of printf Arguments on page 381 for more information If you re using Xlib initialize Xlib s internationalization state after calling setlocale See Initialization for Xlib Pro
460. tion that the new process should execute The new process begins execution in that function and when that function returns the process is terminated Read the sproc 2 reference page for details on the flags that specify which process attributes a child process shares with its parent and for other comparisons between fork and sproc Note The sproc and sprocsp functions are not available for use in a threaded program see Chapter 13 Thread Level Parallelism The pthreads library uses lightweight processes to implement threading and has to control the creation of processes Also when your program uses the MPI library see Chapter 14 Message Passing Parallelism the use of sproc and sprocsp can cause problems 263 Chapter 12 Process Level Parallelism 264 Process Management Certain system functions give you some control over the processes you create The prctl function offers a variety of operations These are some of the most useful PR_MAXPROCS PR_MAXPPROCS PR_GETNSHARE PR_GETSTACKSIZE PR_SETSTACKSIZE PR_RESIDENT Query the system limit on processes per user also available from sysconf _SC_CHILD_MAX see sysconf 2 Query the maximum number of CPUs that are available to the calling process and its children This reflects both the system hardware and reservations made on CPUs but does not reflect system load Query the number of processes in the share group with the calling proce
461. to use fonts with the X Window System The X Window System has several font utilities This section covers a few of the most useful utilities and includes e Listing and Viewing Fonts explains using the x sfonts command e Viewing Fonts describes the xfd command e Getting the Current X Font Path covers the xset command e Changing the X Font Path explains the xset fp command For a complete description of the utilities refer to your X Window System documentation Listing and Viewing Fonts Getting a List of Font Names and Font Aliases To find out which font names and font aliases are known to the X Window System use the command x sfonts For more information about that command see the reference page xlsfonts 1 If you enter the command xlsfonts more the resulting display contains entries such as adobe courier bold o normal 0 0 0 0 m 0 iso8859 1 adobe courier bold o normal 14 100 100 100 m 90 is08859 1 sgi screen medium r normal 14 140 72 72 m 70 is08859 1 screenl4 315 Chapter 15 Working With Fonts 316 The first entry is an example of a 14 part X name for an outline scalable font Numeric parts of font names are set to zero for outline fonts because those fonts can be scaled to various sizes The second and third entries are examples of 14 part X font names for bitmap fonts while the last entry is an alias for the third entry An X program can get a list
462. ttempt to access data beyond that point causes a SIGBUS signal Describing the Mapped Object Three of the mmap parameters describe the object to be mapped into memory which is the backing store of the new segment fd A file descriptor returned by open or by the POSIX defined function shm_open see the open 2 and shm_open 2 reference pages All mmap calls require a file descriptor to define the backing store for the mapped segment The descriptor can represent a file or it can be based on a pseudo file that represents kernel memory or a device special file off The offset into the object represented by fd where the mapped data begins When fd describes a disk file off is an offset into the file When fd describes memory off is an address in that memory off must be an integral multiple of the memory page size see Interrogating the Memory System on page 11 len The number of bytes of data from fd to be mapped The initial size of the segment is len rounded up to a multiple of whole pages Describing the New Segment Three parameters of mmap describe the segment to be created addr Normally 0 to indicate that IRIX should pick a convenient base address addr can specify a virtual address to be the base of the segment See Choosing a Segment Address on page 21 prot Access control on the new segment You use constants to specify a combination of read write and execute permission The access control can be cha
463. ty is specified in the flags The text comes from a message catalog or a default as specified in the format and the label is specified earlier by the application In the example above if no label has been set we get only the output ERROR Permission denied Strings and Message Catalogs Typically an application sets the label once early in its life subsequent error messages have the label prepended For example setlabel UX myprog pfmt stderr MM_ERROR MQ 64 Permission denied would produce by default UX myprog ERROR Permission denied For details consult the pfmt 3 and setlabel 3 reference pages Format Strings for pfmt pfmt format strings are of this form catalog messagenum defaultstring The catalog field is in the format described in Specifying MNLS Catalogs on page 377 messagenum is the message number in the catalog to use as the format defaultstring specifies the string to use if the catalog lookup fails for any reason An important feature of pfmt is its ability to refer to format arguments in format specified order just as printf does See Variably Ordered Referencing of printf Arguments for details Using fmtmsg fmtmsg is a comprehensive formatter using the MNLS catalogs and standard formats You probably won t need to use it most applications should get by with pfmt gettxt and printf Consult the fmtmsg 3 reference
464. ty no longer supported 198 scheduling operations 200 signal use 203 Australia country code 415 Austria country code 415 419 Index backing store 6 9 13 28 barrier 82 IRIX 92 Belgium country code 415 Brazil country code 415 brk 6 7 BSD and IPC 46 Cc calloc 9 catalogs See message catalogs Challenge Onyx architecture PIO error latency 21 character sets See internationalization character sets Chile country code 415 China country code 415 chkconfig command 9 chmod command 19 C local value 344 codes country 415 codesets See internationalization codesets Colombia country code 415 compare and swap 93 95 compiler intrinsic 95 compiler intrinsic for atomic operations 95 condition variable 81 292 297 conventions syntax Xxxv country codes 415 418 Courier font 313 ctype character classification 357 cycle counter 135 420 D data segment locking 25 deadlocks 190 Denmark country code 416 dev mem 20 dev mmem 20 dev ome 20 dev zero and mmap 15 19 direct disk output 231 disk output synchronous 229 synchronous direct 231 DSO text segment for 4 E editres 409 Egypt country code 416 empty strings 342 encodings See internationalization encodings EUC encoding Chinese 387 German 387 Japanese 386 exec new address space 5 F fentlQ example code 239 file mapping into memory 15 26 file access permissions and mmap 1
465. uaranteed transfer capacity becomes available for other processes to reserve When a guarantee expires but the file is not closed the file remains usable for ordinary I O with no guarantee of rate PART FOUR Models of Parallel Computation Chapter 10 Models of Parallel Computation Provides an overview of the different models around which you can design a parallel or distributed application in Silicon Graphics systems Chapter 11 Statement Level Parallelism Gives an overview of the use of Power Fortran and Power C to execute do loops across multiple CPUs Chapter 12 Process Level Parallelism Describes the use of IRIX processes to execute in parallel within one address space or in multiple address spaces Chapter 13 Thread Level Parallelism Describes the use of POSIX threads IEEE 1003 1c for parallel execution within a single address space Chapter 14 Message Passing Parallelism Describes two different facilities for distributing an application across multiple host computers PVM and MPI Chapter 10 Models of Parallel Computation You design a program to perform computations in parallel in order to get higher performance by bringing more hardware to bear on the problem concurrently In order to succeed you need to understand the hardware architecture of the target system and also the software interfaces that are available The purpose of this chapter is to give a high leve
466. ue addressing the queue by its ID S msgsnd i 50 t 17 S msgctl i 50 owner 1110 20 perms 100600 max bytes 32768 1 msgs 64 bytes on queue The maximum queue size is changed this time addressing the queue by its key msgctl k 9 b 1024 owner 1110 20 perms 100600 max bytes 1024 1 msgs 64 bytes on queue A second message is sent msgsnd i 50 t 18 msgctl i 50 owner 1110 20 perms 100600 max bytes 1024 2 msgs 128 bytes on queue The first and second messages are received msgrcev k 9 1 type 17 len 64 text 00001 Thu Jun 20 09 32 55 1996 S msgrcev i 50 1 type 18 len 64 text 00001 Thu Jun 20 09 33 18 1996 Another message receipt is attempted first with IPC_NOWAIT msgrcev i 50 n msgrcv No message of desired typ Another message is attempted without IPC_NOWAIT While msgrcv is suspended the message queue is removed msgrcv k 9 amp 12477 iperm q 50 msgrcv Identifier removed 159 Chapter 6 Message Queues 160 Example of msgget The program msgget in Example 6 5 allows you to create a message queue from the command line The following command line arguments are supported k key Numeric identifier of a message queue for example k 99 p perms Access permissions to set for example p 0664 X Use the IPC_EXCL flag with msgget c Use the IPC_CREAT flag with msgget If the k argument is omitted the program uses a priva
467. uery allocation statistics see amallinfo 3 for structure fields The address of an object allocated using usmalloc or a related function is a valid address in any process that is attached to the shared arena If the address is passed to a process that has not attached the arena the address is not valid for that process and its use will cause a SIGSEGV The usmalloc family of functions is based on the arena allocation function family described in the amalloc 3 reference page The usmallopt function is the same as the amallopt function and both provide several options for modifying the memory allocation methods in a particular arena In a similar way usmallinfo is the same as amallinfo and both return detailed statistics on usage of memory allocation in one arena 65 Chapter 3 Sharing Memory Between Processes 66 Exchanging the First Datum The processes using a shared arena typically need to locate some fundamental data structure that has been allocated within the arena For example the parent process creates a foundation data structure in the arena and initializes it with pointers to other objects within the arena Any process starting to use the arena needs the address of the foundation structure in order to find all the other objects used by the application The shared arena has a special one pointer field for storing such a basic address This area is accessed using the functions summarized in Table 3 5
468. ues struct semid_ds ds info struct union semun arg4 int c semid way to pass amp ds properly aligned while 1 c switch c 102 getopt argc argv k p s xc IRIX Facilities for Mutual Exclusion case k key key key_t strtoul optarg NULL 0 break case s setsize nsems int strtoul optarg NULL 0 break case p permissions perms int strtoul optarg NULL 0 break case c semflg IPC_CREAT break case x semflg IPC_EXCL break default unknown or missing argument return 1 semid semget key nsems semflg perms if 1 semid printf semid d n semid arg4 buf amp ds if 1 semctl semid 0 IPC_STAT arg4 printf owner uid gid d d creator uid gid d d mode 0 o nsems d n ds sem_perm uid ds sem_perm gid ds sem_perm cuid ds sem_perm cgid ds sem_perm mode ds sem_nsems else perror semctl IPC_STAT else perror semget return errno 103 Chapter 4 Mutual Exclusion semmo ap include include include include int main key_ int int int int int stru 104 Example Uses of semctl for Management The program in Example 4 4 semmod allows you to call semctl from the command line to display the size permissions and owner and creator IDs of a semaphore set a
469. unction inWait0 under Asynchronous I O Example on page 209 This function is used when the aiocb is initialized with SIGEV_NONE meaning that no notification is to be returned at the completion of the operation The function waits for an asynchronous operation to complete using a loop in the general form shown in Example 8 2 About Synchronous and Asynchronous I O Example 8 2 Polling for Asynchronous Completion int waitForEndOfAsyncOp aiocb pab while EINPROGRESS ret aio_error pab sginap 0 return ret The function result is the final return code from the read write or sync operation that was started Checking for Completion You have a wide variety of design options other than polling Your program can e Use aio_suspend to wait until one of a list of operations completes e Set up an empty signal handler function and use sigsuspend or sigwait to wait until a signal arrives see the sigsuspend 2 and sigwait 3 reference pages e Use either a signal handler function or a callback function to report completion for example the function can post a semaphore Most of these methods are demonstrated in the example program under Asynchronous I O Example on page 209 Establishing a Completion Signal You request a signal from an asynchronous operation by setting these values in the aiocb refer to usr include nio h and usr include sys signal h aio_sigevent sigev_notify S
470. unction to release an element returned by getFromList Ay void freeInList listHead_t lp element_t ep assert ep gt busyFlag pthread_mutex_lock amp lp gt mutList lock list to prevent races ep gt busyFlag 0 pthread_cond_signal amp ep gt notBusy pthread_mutex_unlock amp lp gt mutList Public function to delete a list element returned by getFromList xy void deleteInList listHead_t lp element_t ep element_t epp assert ep gt busyFlag pthread_mutex_lock amp lp gt mutList for epp amp lp gt head ep epp epp amp epp gt next finding anchor of ep in list epp ep gt next remove ep from list ep gt busyFlag 0 pthread_cond_broadcast amp ep gt notBusy pthread_mutex_unlock lp gt mutList pthread_cond_destroy amp ep gt notBusy free ep The functions in Example 13 3 implement part of a simple library for managing lists In a list head mutList is a mutex object that represents the right to modify any part of the list The elements of a list can be busy that is in use by some thread An element that is busy has a nonzero busyFlag field Synchronizing Pthreads The getFromList function looks up an element in a specified list makes that element busy and returns it The function begins by acquiring the list mutex This ensures that the list cannot change while the function is searching the list
471. upports dynamic process groups that is groups whose membership can change dynamically at any time during a computation MPI does not support dynamic process groups MPI does not provide a mechanism to build a group from scratch but only from other groups that have been defined previously Closely related to groups in MPI are communicators which specify the communication context for a communication operation and an ordered process group that shares this communication context The chief difference between PVM groups and MPI communicators is that any PVM task can join leave a group independently whereas in MPI all communicator operations are collective A PVM task can add or delete a host from the virtual machine thereby dynamically changing the number of machines a program runs on This is not available in MPI A PVM program or any of its tasks can request various kinds of information from the PVM library about the collection of hosts on which it is running the tasks that make up the program and a task s parent The MPI library does not provide such calls Some of the collective communication calls in PVM for instance pym_reduce are nonblocking The MPI collective communication routines are not required to return as soon as their participation in the collective communication is complete PVM provides two methods of signaling other PVM tasks sending a UNIX signal to another task and notifying a task about an event from a set of p
472. urns the status of an asynchronous operation aio_fsync 3 Waits for all scheduled output for a file to complete aio_cancel 3 Cancels pending scheduled operations Each of these functions is described in detail in a reference page 197 Chapter 8 Using Asynchronous I O 198 Asynchronous I O Control Block Each asynchronous I O request is represented by an instance of struct aiocb a data structure that your program must allocate The important fields are as follows e The file descriptor that is the target of the operation File descriptors are returned by open see the open 2 reference page A file descriptor used for asynchronous I O can represent any file or device not only a disk file e The address and size of a buffer to supply or receive the data e The file position for the operation as it would be passed to Iseek see the lseek 2 reference page The use of this value is discussed under Multiple Operations to One File on page 208 e A sigevent structure whose contents indicate what if anything should be done to notify your program of the completion of the I O The use of the sigevent is discussed under Checking for Completion on page 203 Note The IRIX 5 2 implementation also accepted a request priority value Request priorities are no longer supported The request priority field of aiocb exists for compatibility and for possible future use but must currently contain zero Initializi
473. use pthread_attr_setdetachstate to specify that a thread should be detached automatically when it terminates Do this when you know that the thread will not be joined or detached by an explicit function call Initial Scheduling Scope Priority and Policy You can specify an initial thread scheduling scope by calling pthread_attr_setscope and passing one of the scope constants PTHREAD_SCOPE_SYSTEM or PTHREAD_SCOPE_PROCESS in the pthread_attr_t object By default process scope is selected and scheduling is performed by the thread runtime but thread scheduling by the kernel is provided with the system scope attribute System scope threads run at real time policy and priority and may be created only by privileged users You can specify an initial thread priority in a struct sched_param object in memory the structure is declared in sched h Set the desired priority in the sched_priority field Pass the structure to pthread_attr_setschedparam You can specify an initial scheduling policy by calling pthread_attr_setschedpolicy passing one of the policy constants SCHED_FIFO or SCHED_RR Creating Pthreads The pthread_attr_setinheritsched function is used to specify in the attribute object whether a new thread s scheduling policy and priority should be taken from the attribute object or whether they should be inherited from the thread that creates the new thread When you set an attribute object for inheritance the scheduling pol
474. ustments to the system time by a time daemon The Silicon Graphics hardware cycle counter always increases at a steady rate However the cycle counter has a limited precision that depends on the hardware You can use the syssgi system function to find out the precision of the cycle counter see syssgi 2 and look for the SGI_CYCLECNTR_SIZE option Using Interval Timers You create an interval timer object by calling timer_create To this function you pass codes that specify the time base to use and the signal to send upon timer expiration It returns an ID value to identify the timer to other functions The time base for a timer is either CLOCK_REALTIME or CLOCK_SGI_FAST the latter is anonportable request Typically CLOCK_SGI_FAST has finer resolution but you can verify that using the clock_getres function as shown in Example 5 1 You also pass a sigevent_t object to timer_create In it you would normally set the following values sigev_notify SIGEV_SIGNAL to have the timer generate a signal on expiration sigev_signo The signal number you want sent possibly selected from the POSIX real time range for example SIGRTMIN 1 sigev_value sival_int An extra value to be passed to the signal handling function or sigev_value sival_ptr to sigwait when the signal is delivered 133 Chapter 5 Signalling Events 134 You can pass a NULL instead of the address of a sigevent_t In that case the timer signals with a SIGALRM
475. utside of ASCII that break some non arithmetic assumptions Consider the German character which is a lowercase alphabetic character letter yet has no uppercase Consider also French as written in France where the uppercase of is E not Clearly the programmer of an internationalized application has no way of directly computing all the character associations that were available in English under ASCII Strict avoidance of arithmetic on character values should remove any trouble in this area The macros in ctype h are table driven and are therefore locale sensitive If you think of characters as abstract characters rather than as the numbers used to represent them you can avoid pitfalls in this area Locale Specific Behavior Regular Expressions XPG 4 specifies some extensions to traditional regular expression syntax for internationalized software Few application developers do their own regular expression parsing and matching however so we do not include full details here Briefly the extensions provide the ability to specify matches based on e character class such as alpha digit punct or space e equivalence class for instance a 4 a A A A and A may be equivalent e collating symbols allowing you to match the Spanish ch as one element because it is a single collating token e generalization of range specifications of the form c c to include the above If you are processing expressions see the desc
476. v t The op can Full be add sub or and xor and nand Atomically execute t p p v t Backward Atomically execute p 0 Forward Atomically execute w p p v 1 0 Full Issue the MIPS 3 instruction sync to synchronize Full the cache with memory 95 Chapter 4 Mutual Exclusion 96 Each of the compiler intrinsics except __synchronize causes the compiler to generate inline code using Load Linked and Store Conditional to update memory predictably In this respect they are similar to the library functions documented in the test_and_set 3 and uscas 3 reference pages For example the statement __add_and_fetch amp shared 1 j is functionally equivalent to the library call test_then_add amp amp shared 1 j The compiler intrinsic ___compare_and_swap is simpler to use than uscas since you do not have to create a shared memory arena first and avoids the overhead of a system call The compiler intrinsics are different from the library functions and different from an assembly language subroutine you might write in one important way The optimizer phases of the compiler recognize these intrinsics as barriers to code motion The Barrier column in Table 4 10 shows this effect For example the compiler cannot move code in either direction across s use of __compare_and_swap However it can move code backward but not forward across __lock_test_and_set You can make the code motion
477. v zero 19 Over the Spot style 398 P page copy on write 10 locking 23 read only 10 releasing unneeded 29 page fault prevent by locking memory 23 page size 5 page validation 9 parallel computation 243 253 hardware support for 244 models of 247 253 MPI 253 process level 248 261 271 PVM 253 self dispatching process 269 Index SHMEM 252 statement level 251 255 260 thread level 249 273 299 parallel hardware 244 parallelism See parallel computation parallel programming 49 path fonts 318 plockQ example of 25 polld 88 polled semaphore 88 Portugal country code 417 POSIX and IPC 46 POSIX threads See pthreads PostScript printers 329 printers PostScript 329 printfO 381 printf message catalogs 381 process 261 271 address space 4 compared to pthread 274 creation 262 parallelism 248 parent 265 reaping 265 scheduling 266 269 self dispatching 269 share group 262 process scheduling BSD 266 IRIX 266 POSIX 268 process scope threads 286 programming fonts 314 parallel 49 ps command 6 pscommand 10 pthread_mutexattr_setpshared 291 pthread_mutexattr_settype 292 pthread_setconcurrency 286 pthread_setrunon_np 286 pthreads 249 273 299 cancel 282 compare to process 274 compiling 276 creating 277 debugging 277 detach 278 283 fork event 281 priority 288 scheduling 279 286 288 signal action in 285 signal masks 285 stack all
478. ven force a parallelized program to execute on a single CPU when necessary MIPSpro Fortran 77 and MIPSpro Fortran 90 also recognize additional environment variables that specify a range of process numbers and use more or fewer processes within this range as system load varies See the Programmer s Guide for the language for details At certain points the multiple processes must wait for one another before continuing They do this by waiting in a busy loop for a certain length of time then by blocking until they are signaled You can specify the amount of time that a process should spend spinning before it blocks using either source directives or an environment variable see the Programmer s Guide for the language for system functions for this purpose Choosing the Loop Schedule Type Most parallel sections are loops The benefit of parallelization is that some iterations of the loop are executed in one CPU concurrent with other iterations of the same loop in other CPUs But how are the different iterations distributed across processes The languages support four possible methods of scheduling loop iterations as summarized in Table 11 2 Table 11 2 Loop Scheduling Types Schedule Purpose SIMPLE Each process executes LN P iterations starting at Q LN P First process to finish takes the remainder chunk if any DYNAMIC Each process executes C iterations of the loop starting with the next undone chunk unit returning for anot
479. ween the threads and the pages they use However it does ensure that the data will be served by multiple hub chips Using Dynamic Page Migration Dynamic page migration can be enabled for a specific program or for all programs When migration is enabled IRIX keeps track of the source of the references to each page of memory When a page is being used predominately from a different node IRIX copies the page contents to the node that is using it and resets the page tables to direct references to the new location Dynamic migration is a relatively expensive operation besides the overhead of a daemon that uses hardware counters to monitor page usage a migration itself entails a memory copy of data and the forced invalidation of translate lookaside registers in all affected nodes see Page Numbers and Offsets on page 5 For this reason migration is not enabled by default The system administrator can turn it on for all programs using the sn command as described in the sn 1 reference page but this is not recommended You can experiment to see whether dynamic page migration helps a particular program It is likely to help when the initial placement of data is not optimal and when the program maintains consistent access patterns for long periods many seconds to minutes When the program has variable inconsistent access patterns migration can hurt performance by causing frequent unhelpful page movements 41 Chapter 1 Process Add
480. will need to catalog their strings Some will need to use library routines for character sorting or locale dependent date time or number formatting A few whose applications use the eighth bit of 8 bit characters inappropriately will need to stop doing so The few applications that do arithmetic to manipulate characters will need to be cleaned up Some GUI designers will have to spend just a little more time thinking But for the large majority of developers there isn t much to do Overview of Internationalization The information presented in the following sections addresses internationalization issues pertinent to a developer some sections however may not be relevant to your applications Standards IRIX internationalization includes these standards compliant features among others ANSI C and POSIX ISO 9945 1 Locale X OPEN Portability Guide Issue 4 XPG 4 XPG 4 message catalogs interpretation of locale strings UNIX System V Release 4 Multi National Language Support MNLS message catalogs X11R5 and X11R6 Input methods text rendering resource files Internationalizing Your Application The Basic Steps To internationalize your icon follow these steps 1 2 3 4 Call setlocale as soon as possible to put the process into the desired locale See Setting the Current Locale on page 340 for instructions Make your application 8 bit clean An application is 8 bit clean if it does not use the h
481. y 201 Checking the Progress of Asynchronous Requests 202 Polling for Status 202 Checking for Completion 203 Establishing a Completion Signal 203 Establishing a Callback Function 204 Holding Callbacks Temporarily 207 Multiple Operations to One File 208 Asynchronous I O Example 209 High Performance File I O 229 Using Synchronous Output 229 About Buffered Output 229 Requesting Synchronous Output 230 Using DirectI O 231 Direct I O Example 231 Using a Delayed System Buffer Flush 236 xiii Contents Using Guaranteed Rate I O 236 About Guaranteed Rate I O 236 About Types of Guarantees 237 About Device Configuration 237 Creating a Real time File 238 Requesting a Guarantee 239 Releasing a Guarantee 240 10 Models of Parallel Computation 243 Parallel Hardware Models 244 Parallel Programs on Uniprocessors 245 Types of Memory Systems 245 Single Memory Systems 245 Multiple Memory Systems 246 Hierarchic Nonuniform Memory Systems 247 Parallel Execution Models 247 Process Level Parallelism 248 Thread Level Parallelism 249 Statement Level Parallelism 251 Message Passing Models 251 Shared Memory GHMEM Model 252 Message Passing Interface MPI Model 253 Parallel Virtual Machine PVM Model 253 11 Statement Level Parallelism 255 Products for Statement Level Parallelism 256 Silicon Graphics Support 256 Products from Other Vendors 256 Creating Parallel Programs 257 xiv Contents Managing Statement Parallel Execution 258 Contr
482. y data that is unique to a thread is the contents of its local variables on the stack and these do not persist between calls However the pthreads library provides a way to create persistent thread unique data The functions for this are summarized in Table 13 5 Table 13 5 Functions for Thread Unique Data Function Purpose pthread_key_create 3P Create a key pthread_key_delete 3P Delete a key pthread_getspecific 3P Retrieve this thread s value for a key pthread_setspecific 3P Set this thread s value for a key Your program calls pthread_key_create to define a new storage key Once created a key may be used by all threads to identify a unique key value Any thread can use pthread_getspecific to retrieve that thread s unique value stored under a key A thread can fetch only its own value which is the value stored by this same thread using pthread_setspecific The initial stored value is NULL When you create a key you can specify a destructor function that is called automatically when a thread terminates The destructor is called while the key is valid and the key value for the terminating thread is not NULL The destructor receives the thread s key value as its argument Pthreads and Signals 284 For a general overview of signal concepts and numbers see Signals on page 113 and the signal 5 reference page IRIX supports three different signal facilities BSD signals SVR4 signals and POSIX signa
483. y to start the main operation calls barrier passing the address of the barrier and the number of processes that will meet When that many processes have called barrier all of them are released to begin execution Barriers are part of IRIX IPC and require the use of a shared arena Barriers cannot be used to coordinate POSIX threads POSIX Facilities for Mutual Exclusion 82 The POSIX real time extensions detailed in IEEE standard 1003 1b include named and unnamed semaphores The POSIX threads library detailed in IEEE standard 1003 1c introduces mutexes and condition variables POSIX Facilities for Mutual Exclusion Managing Unnamed Semaphores An unnamed semaphore is a semaphore object that exists in memory only An unnamed semaphore can be identified only by its memory address so it can be shared only by processes or threads that share that memory location The functions for creating and freeing unnamed semaphores are summarized in Table 4 1 Table 4 1 POSIX Functions to Manage Unnamed Semaphores Function Name Purpose and Operation sem_init 3 Initialize a semaphore object setting its value and preparing it for use sem_destroy 3 Make a semaphore unusable The type of a POSIX semaphore is sem_t which is declared in the header file semaphore h You create an unnamed semaphore by allocating memory for a sem_t variable either dynamically or statically and initializing it with sem_init The function in Example
484. ys e Static assignment of the constant PTHREAD_COND_INITIALIZER e Calling pthread_cond_init passing NULL instead of the address of an attribute object e Calling pthread_cond_init passing a pthread_condattr_t object that you have set up with attribute values The first two methods initialize the variable to default attributes By default only threads within a process share a condition variable Using pthread_condattr_setpshared you can allow any thread from any process with access to the condition variable memory location to use the condition variable Enable condition variable sharing by changing the default PTHREAD_PROCESS_PRIVATE attribute to PTHREAD_PROCESS_SHARED 293 Chapter 13 Thread Level Parallelism 294 Using Condition Variables A condition variable is a software object that represents a test of a Boolean condition Typically the condition changes because of a software event such as other thread has supplied data A thread establishes that it needs to wait by first evaluating the condition The thread that satisfies the condition signals the condition variable releasing one or all threads that are waiting For example a thread might acquire a mutex that represents a shared resource While holding the mutex the thread finds that the shared resource is not complete The thread does three things e Wait giving up the mutex so that some other thread can renew the shared resource e Wait until the co

Thread-Level Parallelism

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