PTF DVFS Plugin User's Guide
Contents
1. include with boost lib BOOST_LIBDIR with xerces include XERCES_BASE include with xerces lib XERCES_BASE lib enable papi with papi include PAPI BASE include with papi lib PAPI_BASE lib prefix HOME install periscope enable enopt with enopt include ENOPT_BASE include with enopt lib ENOPT_BASE lib CHAPTER 2 QUICK START 4 The next step is to build and install the DVFS Plugin using the following commands in the terminal window make j 16 install and then make install It must be assured that the PAPI library was compiled with the RAPL component support This PAPI component uses the RAPL library which allows in Sandy Bridge EP and Ivy Bridge architectures the access to the energy and power sensors To check this the following command must be run papi_native_avail If the output contains the string rapl PPO_ENERGY PACKAGEO rapl PPO_ENERGY PACKAGE1 Then the PAPI library has RAPL support and thus the energy measure ments can be performed Otherwise please refer to the PAPI documentation on how to compile PAPI with the RAPL support Note Depending on the Linux kernel and kernel settings used the command papi_native_avail may required privileged permissions root to list the above RAPL counters If this requirement is not fulfilled for these kernels the strings will not appear even if the energy counters are available 2 2 Running DVFS Plugin The DVFS plugin runs with2. TF PTF DVFS Plugin User s Guide PTF Version 1 1 DVFS Plugin Version 1 1 Carla Guillen 13 04 2015 Contents 1 Introduction 2 2 Quick Start 3 2 1 Basic configuration eeen 3 2 2 Running DVFS Plugin 4 2 3 Execution results 2 22 ee 5 3 DVFS Autotuning Approach 6 3 1 Tuning parameter 5 5405 6 2s eee ed ee 6 3 2 Search strategy veces e sera ek us ee de ee eae ole a 6 3 3 Tuning scenario aoaaa 6 3 4 Tuning action ae 7 8 ee eee 8 4 2 Configuration of the Domain to Change the Frequency 10 3 Configuration of the Number of Neighbors in the Search Space 10 5 How To Use the Tuning Advice 12 Chapter 1 Introduction One of the main goals of the DVFS Plugin is to minimize the amount of en ergy that the HPC system uses when executing an application One method of reducing the energy is to lower the clock frequency of the processors which is possible in modern processors However manual tuning of processor fre quencies for parallel applications to obtain an optimal energy to solution can be extremely time consuming So it is important to provide an automatic tool that enables the user to e Measure the energy consumption of processors e Analyze the performance and energy data from the application e Provide the optimal energy to solution configuration for the given ap plication e Set the new core frequency and the userspace governor during the application runtime The Per
3. ed correctly For this cases it is convenient to set the PSC_FREQ_TO_ALL_NODE environment variable to one such that the master process or the task that runs in a sequential region in the case of OpenMP will change the frequency of the entire node there are two processors in a node Note that the downside of this is the increased latency of the changes in frequency Example Setting the frequency from the master process to all the node is done as follows Exporting the environment variable should be done before running the PTF command export PSC_FREQ_TO_ALL_NODE 1 psc_frontend apprun lt APPLICATION_NAME gt mpinumprocs lt MPI_PROCS gt tune dvfs force localhost 4 3 Configuration of the Number of Neighbors in the Search Space The environment variable PSC_FREQ_NEIGHBORS specifies the number of neigh boring frequencies that will be searched in the experimentation By default only one neighboring frequency which is higher and one neighboring fre quency which is lower than the predicted frequency will be used However if the PSC_FREQ_NEIGHBORS environment variable is set the number of neigh bors to the right and to the left of the predicted frequency will be used CHAPTER 4 ADVANCED CONFIGURATION 11 Example The following setting will allow to experiment with the frequen cies in the range fp a fp 4 In this case fp is the predicted frequency export PSC_FREQ_NEIGHBORS 4 Only a maximum of seven neighboring f
4. ilable models and the corresponding ids that can be used to set them with the PSC_DVFS_MODEL environment variable Model PSC DVFS MODEL id number Model Energy 1 1 Model Energy 2 2 Energy 3 Delay Product TCO 4 Power Capping 5 Model Policy 1 6 Model Policy 2 7 Model Policy 3 8 Model Policy 4 9 Table 4 1 Available models and ids Example Choosing TCO as tuning objective and running the DVFS plu gin is done as follows Check in Table the identification number of the TCO model the id number is on the second column and set is as environment variable before CHAPTER 4 ADVANCED CONFIGURATION 10 running PTF with the plugin as shown below export PSC_DVFS_MODEL 4 psc_frontend apprun lt APPLICATION_NAME gt mpinumprocs lt MPI_PROCS gt tune dvfs force localhost 4 2 Configuration of the Domain to Change the Frequency The environment variable PSC_FREQ_TO_ALL_NODE specifies how the plugin will change the frequencies of the processors By default the plugin changes only the frequency of one core from a task or a thread Intel Sandy Bridge EP processors change the frequency at the level of the processor each pro cessor contains 8 cores If the set frequencies are different in a processor the architecture takes the highest frequency set for all the cores and applies this to the entire processor If not all cores in a processor are being used for an application the change of frequency may not be perform
5. in the Periscope Tuning Framework as a plugin It can be started using the normal psc_frontend command refer to the PTF User s Guide In that case the tune flag must be configured in order to specify the DVFS plugin tune dvfs For instance running a certain application in localhost with a concrete num ber of tasks should look like psc_frontend apprun lt APPLICATION_NAME gt mpinumprocs lt MPI_PROCS gt tune dvfs force localhost This command will start the application and the DVFS tuning strategy CHAPTER 2 QUICK START 5 2 3 Execution results Once the application finishes correctly and upon completion of the tuning measurements the DVFS shows the results for three CPU frequencies The DVFS predicts one frequency based on an energy time and power model The predicted frequency as well as two other neighboring frequencies one lower and one higher to the predicted frequency if available are used for the experiments By the default only these three frequencies are used However the plugin can be configured to increase the search space by increasing the number of neighboring frequencies As an example a possible output of the plugin running a certain application is presented below the output is slightly modified to fit the page Found Optimum Scenario Region id USER_REGION file1 f90 4 Optimum Scenario 2 Frequency 1700 Region id USER_REGION file2 f90 11 Optimum Scenario 4 Freque
6. iscope Tuning Framework PTF provides a mechanism that auto matically extracts the information required for tuning the system The PTF DVFS plugin provides a mechanism to tune the processor frequencies based on the analysis of the data provided by the PTF to produce the optimal energy to solution configuration for the specific parallel application The DVFS plugin relies on energy power and time models to reduce the search space for tuning The models use performance data collected at the pre analysis stage The frequency that the model predicts as consuming the minimum energy consumption is calculated by the plugin The neighboring frequencies of the predicted frequency are explored via experiments by the plugin and the best frequency among all three is given as an output Chapter 2 Quick Start The DVFS Plugin is installed along with the Periscope Tuning Framework Please refer to the PTF Installation Guide for a complete description of the installation process 2 1 Basic configuration Set the environment variables as described in the PTF Installation Manual Make sure you use the following module module load enopt 1 3 To configure the build environment for the DVFS we use the following con figure command within a terminal window mkdir lt build directory gt cd lt build directory gt lt path to source code directory gt configure with ace include ACE BASE with ace lib ACE_LIBDIR with boost include BO0ST_BASE
7. ments directly by using the reference frequency Model Energy 2 optimizes based on power and time measurements of the reference frequency In contrast to model 1 power and time are predicted separately and their product is used Energy Delay optimizes based on the product of energy and runtime Total Cost of Ownership TCO optimizes based on the total cost of ownership The prices of energy are based on current prices used in Germany The cost function is adapted to the SuperMUC in the Leibniz Supercomputing Centre CHAPTER 4 ADVANCED CONFIGURATION 9 Power capping optimizes taking into account a maximum power limit The optimal frequency recommended by the plugin will not surpass the power limit This power limit has been defined as 110 Watt Model Policy 1 optimizes the increase of performance only when it is greater than the increase of energy Normalized energy values are used to compare the increase of energy Model Policy 2 optimizes the increase of performance only when it is greater than the increase of power Normalized energy values are used to compare the increase of power Model Policy 3 optimizes by staying below a powercap 110W or by having a significant performance increase a factor 1 1 performance increase Model Policy 4 optimizes by considering a maximum performance degra dation with respect to the nominal frequency of no more than 10 and staying below a powercap 110W Table shows the different ava
8. ncy 1900 Region id USER_REGION file2 f90 27 Optimum Scenario 0 Frequency 1500 Search Path Scenario Governor Freq Energy Runtime EDP Region MHz J s 4 4 4444 0 Userspace 1500 2810 000 19 163 53849 154 USER_REGION file1 f90 4 0 Userspace 1500 362 000 1 558 564 137 USER_REGION file2 90 11 0 Userspace 1500 1729 000 17 526 30302 454 USER_REGION file2 f90 27 ened 9 Userspace 2400 2922 000 12 466 36424 775 USER_REGION file1 f90 4 9 Userspace 2400 363 000 1 558 565 706 USER_REGION file2 90 11 9 Userspace 2400 2403 000 10 810 25977 391 USER_REGION file2 90 27 Other data Scenario Governor Freq Avrg Power TCO EDDP Region MHz W node EUR node 4 44 444 0 Userspace 1500 89 859 2 601 1031932 878 USER_REGION file1 f90 4 0 Userspace 1500 119 354 0 224 1879 146 USER_REGION file2 f90 11 0 Userspace 1500 50 097 2 191 531080 809 USER_REGION file2 90 27 ER 9 Userspacel 2400 118 244 1 788 454060 323 USER_REGION file1 f90 4 9 Userspace 2400 119 352 0 224 1881 608 USER_REGION file2 f90 11 9 Userspace 2400 115 167 1 541 280825 990 USER_REGION file2 90 27 Chapter 3 DVFS Autotuning Approach The DVFS plugin follows the general PTF plugin approach refer also to the PTF User s Guide 3 1 Tuning parameter The DVFS plugin employs as a tuning parameter the available CPU fre quencies of the processor excep
9. requencies are taken If the envi ronment variable exceeds this number or is set with negative values the plugin will use the default value one neighbor at each side of fp Chapter 5 How To Use the Tuning Advice Once the application is successfully completed the DVFS plugin displays the list of all tested scenarios identified each of them by its id the specific combination of the tuning parameters applied to that region and the energy and time measurements performed with that configuration as well as the scenario id where the optimal values where found In this case the best scenario is the one that presents a better energy to solution One should call the specific functions to change the frequency provided by the periscope interface as the first code line of the main function setting as parameters the configuration found in the optimum scenario The user can opt to do this automatically by using the enopt library This library uses the same interface as the interface of PTF with the application The instrumented source code can be recompiled and linked only to the enopt library In order to implement the advice the user has to set the environ ment variable PSC_DVFS_ADVICE_FILE which contains one string the path to the enopt advice called advice_enopt_jpidj txt For example export PSC_DVFS_ADVICE_FILE path to advice advice_enopt_134 txt The environment variable must be set before run the application Inter nally during run
10. t for turbomode which is 3 1 GHz for the Intel Sandy Bridge EP processors The Intel Sandy Bridge EP microarchi tecture uses frequencies between 1 2 GHz and 2 7 GHz in steps of 0 1 GHz ie 1 2 1 3 1 4 2 6 and 2 7 GHz 3 2 Search strategy In order to find the best tuning of an application a search through the tuning space has to be performed The DVFS plugin uses a model based search which reduces the search space to three frequencies 3 3 Tuning scenario Based on the strategy consecutive tuning scenarios are then being generated at run time and the energy to solution of the application is evaluated for each of these scenarios CHAPTER 3 DVFS AUTOTUNING APPROACH 7 3 4 Tuning action Applying a scenario to the application means setting the CPU parameters before running the application Therefore the tuning action performed by the DVFS plugin is to set the CPU frequency Chapter 4 Advanced Configuration In the following sections the configuration of the runtime environment is described The plugin can change the objective function and the domains to change the frequency via the two environment variables PSC_DVFS_MODEL and PSC_FREQ_TO_ALL_NODE respectively 4 1 Configuration of the Objective Function If the user does not set the PSC_DVFS_MODEL environment variable the tool will calculate the model based on the Model Energy 1 The following models are available Model Energy 1 optimizes based on energy measure
11. time the application reads these two files and produces a hashed map which contains the file id and the region s first line as the key and the optimized frequency as the map s value These two values are provided by the instrumentation when it inserts the start_region and the stop_region so at runtime the corresponding frequency from the advice will be set on each region 12
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