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SPDX-License-Identifier: GPL-2.0 + +============================================================ +Intel(R) Speed Select Technology User Guide +============================================================ + +The Intel(R) Speed Select Technology (Intel(R) SST) provides a powerful new +collection of features that give more granular control over CPU performance. +With Intel(R) SST, one server can be configured for power and performance for a +variety of diverse workload requirements. + +Refer to the links below for an overview of the technology: + +- https://www.intel.com/content/www/us/en/architecture-and-technology/speed-select-technology-article.html +- https://builders.intel.com/docs/networkbuilders/intel-speed-select-technology-base-frequency-enhancing-performance.pdf + +These capabilities are further enhanced in some of the newer generations of +server platforms where these features can be enumerated and controlled +dynamically without pre-configuring via BIOS setup options. This dynamic +configuration is done via mailbox commands to the hardware. One way to enumerate +and configure these features is by using the Intel Speed Select utility. + +This document explains how to use the Intel Speed Select tool to enumerate and +control Intel(R) SST features. This document gives example commands and explains +how these commands change the power and performance profile of the system under +test. Using this tool as an example, customers can replicate the messaging +implemented in the tool in their production software. + +intel-speed-select configuration tool +====================================== + +Most Linux distribution packages may include the "intel-speed-select" tool. If not, +it can be built by downloading the Linux kernel tree from kernel.org. Once +downloaded, the tool can be built without building the full kernel. + +From the kernel tree, run the following commands:: + +# cd tools/power/x86/intel-speed-select/ +# make +# make install + +Getting Help +------------ + +To get help with the tool, execute the command below:: + +# intel-speed-select --help + +The top-level help describes arguments and features. Notice that there is a +multi-level help structure in the tool. For example, to get help for the feature "perf-profile":: + +# intel-speed-select perf-profile --help + +To get help on a command, another level of help is provided. For example for the command info "info":: + +# intel-speed-select perf-profile info --help + +Summary of platform capability +------------------------------ +To check the current platform and driver capaibilities, execute:: + +#intel-speed-select --info + +For example on a test system:: + + # intel-speed-select --info + Intel(R) Speed Select Technology + Executing on CPU model: X + Platform: API version : 1 + Platform: Driver version : 1 + Platform: mbox supported : 1 + Platform: mmio supported : 1 + Intel(R) SST-PP (feature perf-profile) is supported + TDP level change control is unlocked, max level: 4 + Intel(R) SST-TF (feature turbo-freq) is supported + Intel(R) SST-BF (feature base-freq) is not supported + Intel(R) SST-CP (feature core-power) is supported + +Intel(R) Speed Select Technology - Performance Profile (Intel(R) SST-PP) +------------------------------------------------------------------------ + +This feature allows configuration of a server dynamically based on workload +performance requirements. This helps users during deployment as they do not have +to choose a specific server configuration statically. This Intel(R) Speed Select +Technology - Performance Profile (Intel(R) SST-PP) feature introduces a mechanism +that allows multiple optimized performance profiles per system. Each profile +defines a set of CPUs that need to be online and rest offline to sustain a +guaranteed base frequency. Once the user issues a command to use a specific +performance profile and meet CPU online/offline requirement, the user can expect +a change in the base frequency dynamically. This feature is called +"perf-profile" when using the Intel Speed Select tool. + +Number or performance levels +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +There can be multiple performance profiles on a system. To get the number of +profiles, execute the command below:: + + # intel-speed-select perf-profile get-config-levels + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + get-config-levels:4 + package-1 + die-0 + cpu-14 + get-config-levels:4 + +On this system under test, there are 4 performance profiles in addition to the +base performance profile (which is performance level 0). + +Lock/Unlock status +~~~~~~~~~~~~~~~~~~ + +Even if there are multiple performance profiles, it is possible that they +are locked. If they are locked, users cannot issue a command to change the +performance state. It is possible that there is a BIOS setup to unlock or check +with your system vendor. + +To check if the system is locked, execute the following command:: + + # intel-speed-select perf-profile get-lock-status + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + get-lock-status:0 + package-1 + die-0 + cpu-14 + get-lock-status:0 + +In this case, lock status is 0, which means that the system is unlocked. + +Properties of a performance level +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To get properties of a specific performance level (For example for the level 0, below), execute the command below:: + + # intel-speed-select perf-profile info -l 0 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + perf-profile-level-0 + cpu-count:28 + enable-cpu-mask:000003ff,f0003fff + enable-cpu-list:0,1,2,3,4,5,6,7,8,9,10,11,12,13,28,29,30,31,32,33,34,35,36,37,38,39,40,41 + thermal-design-power-ratio:26 + base-frequency(MHz):2600 + speed-select-turbo-freq:disabled + speed-select-base-freq:disabled + ... + ... + +Here -l option is used to specify a performance level. + +If the option -l is omitted, then this command will print information about all +the performance levels. The above command is printing properties of the +performance level 0. + +For this performance profile, the list of CPUs displayed by the +"enable-cpu-mask/enable-cpu-list" at the max can be "online." When that +condition is met, then base frequency of 2600 MHz can be maintained. To +understand more, execute "intel-speed-select perf-profile info" for performance +level 4:: + + # intel-speed-select perf-profile info -l 4 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + perf-profile-level-4 + cpu-count:28 + enable-cpu-mask:000000fa,f0000faf + enable-cpu-list:0,1,2,3,5,7,8,9,10,11,28,29,30,31,33,35,36,37,38,39 + thermal-design-power-ratio:28 + base-frequency(MHz):2800 + speed-select-turbo-freq:disabled + speed-select-base-freq:unsupported + ... + ... + +There are fewer CPUs in the "enable-cpu-mask/enable-cpu-list". Consequently, if +the user only keeps these CPUs online and the rest "offline," then the base +frequency is increased to 2.8 GHz compared to 2.6 GHz at performance level 0. + +Get current performance level +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To get the current performance level, execute:: + + # intel-speed-select perf-profile get-config-current-level + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + get-config-current_level:0 + +First verify that the base_frequency displayed by the cpufreq sysfs is correct:: + + # cat /sys/devices/system/cpu/cpu0/cpufreq/base_frequency + 2600000 + +This matches the base-frequency (MHz) field value displayed from the +"perf-profile info" command for performance level 0(cpufreq frequency is in +KHz). + +To check if the average frequency is equal to the base frequency for a 100% busy +workload, disable turbo:: + +# echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo + +Then runs a busy workload on all CPUs, for example:: + +#stress -c 64 + +To verify the base frequency, run turbostat:: + + #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1 + + Package Core CPU Bzy_MHz + - - 2600 + 0 0 0 2600 + 0 1 1 2600 + 0 2 2 2600 + 0 3 3 2600 + 0 4 4 2600 + . . . . + + +Changing performance level +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To the change the performance level to 4, execute:: + + # intel-speed-select -d perf-profile set-config-level -l 4 -o + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + perf-profile + set_tdp_level:success + +In the command above, "-o" is optional. If it is specified, then it will also +offline CPUs which are not present in the enable_cpu_mask for this performance +level. + +Now if the base_frequency is checked:: + + #cat /sys/devices/system/cpu/cpu0/cpufreq/base_frequency + 2800000 + +Which shows that the base frequency now increased from 2600 MHz at performance +level 0 to 2800 MHz at performance level 4. As a result, any workload, which can +use fewer CPUs, can see a boost of 200 MHz compared to performance level 0. + +Check presence of other Intel(R) SST features +--------------------------------------------- + +Each of the performance profiles also specifies weather there is support of +other two Intel(R) SST features (Intel(R) Speed Select Technology - Base Frequency +(Intel(R) SST-BF) and Intel(R) Speed Select Technology - Turbo Frequency (Intel +SST-TF)). + +For example, from the output of "perf-profile info" above, for level 0 and level +4: + +For level 0:: + speed-select-turbo-freq:disabled + speed-select-base-freq:disabled + +For level 4:: + speed-select-turbo-freq:disabled + speed-select-base-freq:unsupported + +Given these results, the "speed-select-base-freq" (Intel(R) SST-BF) in level 4 +changed from "disabled" to "unsupported" compared to performance level 0. + +This means that at performance level 4, the "speed-select-base-freq" feature is +not supported. However, at performance level 0, this feature is "supported", but +currently "disabled", meaning the user has not activated this feature. Whereas +"speed-select-turbo-freq" (Intel(R) SST-TF) is supported at both performance +levels, but currently not activated by the user. + +The Intel(R) SST-BF and the Intel(R) SST-TF features are built on a foundation +technology called Intel(R) Speed Select Technology - Core Power (Intel(R) SST-CP). +The platform firmware enables this feature when Intel(R) SST-BF or Intel(R) SST-TF +is supported on a platform. + +Intel(R) Speed Select Technology Core Power (Intel(R) SST-CP) +--------------------------------------------------------------- + +Intel(R) Speed Select Technology Core Power (Intel(R) SST-CP) is an interface that +allows users to define per core priority. This defines a mechanism to distribute +power among cores when there is a power constrained scenario. This defines a +class of service (CLOS) configuration. + +The user can configure up to 4 class of service configurations. Each CLOS group +configuration allows definitions of parameters, which affects how the frequency +can be limited and power is distributed. Each CPU core can be tied to a class of +service and hence an associated priority. The granularity is at core level not +at per CPU level. + +Enable CLOS based prioritization +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To use CLOS based prioritization feature, firmware must be informed to enable +and use a priority type. There is a default per platform priority type, which +can be changed with optional command line parameter. + +To enable and check the options, execute:: + + # intel-speed-select core-power enable --help + Intel(R) Speed Select Technology + Executing on CPU model: X + Enable core-power for a package/die + Clos Enable: Specify priority type with [--priority|-p] + 0: Proportional, 1: Ordered + +There are two types of priority types: + +- Ordered + +Priority for ordered throttling is defined based on the index of the assigned +CLOS group. Where CLOS0 gets highest priority (throttled last). + +Priority order is: +CLOS0 > CLOS1 > CLOS2 > CLOS3. + +- Proportional + +When proportional priority is used, there is an additional parameter called +frequency_weight, which can be specified per CLOS group. The goal of +proportional priority is to provide each core with the requested min., then +distribute all remaining (excess/deficit) budgets in proportion to a defined +weight. This proportional priority can be configured using "core-power config" +command. + +To enable with the platform default priority type, execute:: + + # intel-speed-select core-power enable + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + core-power + enable:success + package-1 + die-0 + cpu-6 + core-power + enable:success + +The scope of this enable is per package or die scoped when a package contains +multiple dies. To check if CLOS is enabled and get priority type, "core-power +info" command can be used. For example to check the status of core-power feature +on CPU 0, execute:: + + # intel-speed-select -c 0 core-power info + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + core-power + support-status:supported + enable-status:enabled + clos-enable-status:enabled + priority-type:proportional + package-1 + die-0 + cpu-24 + core-power + support-status:supported + enable-status:enabled + clos-enable-status:enabled + priority-type:proportional + +Configuring CLOS groups +~~~~~~~~~~~~~~~~~~~~~~~ + +Each CLOS group has its own attributes including min, max, freq_weight and +desired. These parameters can be configured with "core-power config" command. +Defaults will be used if user skips setting a parameter except clos id, which is +mandatory. To check core-power config options, execute:: + + # intel-speed-select core-power config --help + Intel(R) Speed Select Technology + Executing on CPU model: X + Set core-power configuration for one of the four clos ids + Specify targeted clos id with [--clos|-c] + Specify clos Proportional Priority [--weight|-w] + Specify clos min in MHz with [--min|-n] + Specify clos max in MHz with [--max|-m] + +For example:: + + # intel-speed-select core-power config -c 0 + Intel(R) Speed Select Technology + Executing on CPU model: X + clos epp is not specified, default: 0 + clos frequency weight is not specified, default: 0 + clos min is not specified, default: 0 MHz + clos max is not specified, default: 25500 MHz + clos desired is not specified, default: 0 + package-0 + die-0 + cpu-0 + core-power + config:success + package-1 + die-0 + cpu-6 + core-power + config:success + +The user has the option to change defaults. For example, the user can change the +"min" and set the base frequency to always get guaranteed base frequency. + +Get the current CLOS configuration +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To check the current configuration, "core-power get-config" can be used. For +example, to get the configuration of CLOS 0:: + + # intel-speed-select core-power get-config -c 0 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + core-power + clos:0 + epp:0 + clos-proportional-priority:0 + clos-min:0 MHz + clos-max:Max Turbo frequency + clos-desired:0 MHz + package-1 + die-0 + cpu-24 + core-power + clos:0 + epp:0 + clos-proportional-priority:0 + clos-min:0 MHz + clos-max:Max Turbo frequency + clos-desired:0 MHz + +Associating a CPU with a CLOS group +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To associate a CPU to a CLOS group "core-power assoc" command can be used:: + + # intel-speed-select core-power assoc --help + Intel(R) Speed Select Technology + Executing on CPU model: X + Associate a clos id to a CPU + Specify targeted clos id with [--clos|-c] + + +For example to associate CPU 10 to CLOS group 3, execute:: + + # intel-speed-select -c 10 core-power assoc -c 3 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-10 + core-power + assoc:success + +Once a CPU is associated, its sibling CPUs are also associated to a CLOS group. +Once associated, avoid changing Linux "cpufreq" subsystem scaling frequency +limits. + +To check the existing association for a CPU, "core-power get-assoc" command can +be used. For example, to get association of CPU 10, execute:: + + # intel-speed-select -c 10 core-power get-assoc + Intel(R) Speed Select Technology + Executing on CPU model: X + package-1 + die-0 + cpu-10 + get-assoc + clos:3 + +This shows that CPU 10 is part of a CLOS group 3. + + +Disable CLOS based prioritization +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To disable, execute:: + +# intel-speed-select core-power disable + +Some features like Intel(R) SST-TF can only be enabled when CLOS based prioritization +is enabled. For this reason, disabling while Intel(R) SST-TF is enabled can cause +Intel(R) SST-TF to fail. This will cause the "disable" command to display an error +if Intel(R) SST-TF is already enabled. In turn, to disable, the Intel(R) SST-TF +feature must be disabled first. + +Intel(R) Speed Select Technology - Base Frequency (Intel(R) SST-BF) +------------------------------------------------------------------- + +The Intel(R) Speed Select Technology - Base Frequency (Intel(R) SST-BF) feature lets +the user control base frequency. If some critical workload threads demand +constant high guaranteed performance, then this feature can be used to execute +the thread at higher base frequency on specific sets of CPUs (high priority +CPUs) at the cost of lower base frequency (low priority CPUs) on other CPUs. +This feature does not require offline of the low priority CPUs. + +The support of Intel(R) SST-BF depends on the Intel(R) Speed Select Technology - +Performance Profile (Intel(R) SST-PP) performance level configuration. It is +possible that only certain performance levels support Intel(R) SST-BF. It is also +possible that only base performance level (level = 0) has support of Intel +SST-BF. Consequently, first select the desired performance level to enable this +feature. + +In the system under test here, Intel(R) SST-BF is supported at the base +performance level 0, but currently disabled. For example for the level 0:: + + # intel-speed-select -c 0 perf-profile info -l 0 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + perf-profile-level-0 + ... + + speed-select-base-freq:disabled + ... + +Before enabling Intel(R) SST-BF and measuring its impact on a workload +performance, execute some workload and measure performance and get a baseline +performance to compare against. + +Here the user wants more guaranteed performance. For this reason, it is likely +that turbo is disabled. To disable turbo, execute:: + +#echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo + +Based on the output of the "intel-speed-select perf-profile info -l 0" base +frequency of guaranteed frequency 2600 MHz. + + +Measure baseline performance for comparison +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To compare, pick a multi-threaded workload where each thread can be scheduled on +separate CPUs. "Hackbench pipe" test is a good example on how to improve +performance using Intel(R) SST-BF. + +Below, the workload is measuring average scheduler wakeup latency, so a lower +number means better performance:: + + # taskset -c 3,4 perf bench -r 100 sched pipe + # Running 'sched/pipe' benchmark: + # Executed 1000000 pipe operations between two processes + Total time: 6.102 [sec] + 6.102445 usecs/op + 163868 ops/sec + +While running the above test, if we take turbostat output, it will show us that +2 of the CPUs are busy and reaching max. frequency (which would be the base +frequency as the turbo is disabled). The turbostat output:: + + #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1 + Package Core CPU Bzy_MHz + 0 0 0 1000 + 0 1 1 1005 + 0 2 2 1000 + 0 3 3 2600 + 0 4 4 2600 + 0 5 5 1000 + 0 6 6 1000 + 0 7 7 1005 + 0 8 8 1005 + 0 9 9 1000 + 0 10 10 1000 + 0 11 11 995 + 0 12 12 1000 + 0 13 13 1000 + +From the above turbostat output, both CPU 3 and 4 are very busy and reaching +full guaranteed frequency of 2600 MHz. + +Intel(R) SST-BF Capabilities +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To get capabilities of Intel(R) SST-BF for the current performance level 0, +execute:: + + # intel-speed-select base-freq info -l 0 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + speed-select-base-freq + high-priority-base-frequency(MHz):3000 + high-priority-cpu-mask:00000216,00002160 + high-priority-cpu-list:5,6,8,13,33,34,36,41 + low-priority-base-frequency(MHz):2400 + tjunction-temperature(C):125 + thermal-design-power(W):205 + +The above capabilities show that there are some CPUs on this system that can +offer base frequency of 3000 MHz compared to the standard base frequency at this +performance levels. Nevertheless, these CPUs are fixed, and they are presented +via high-priority-cpu-list/high-priority-cpu-mask. But if this Intel(R) SST-BF +feature is selected, the low priorities CPUs (which are not in +high-priority-cpu-list) can only offer up to 2400 MHz. As a result, if this +clipping of low priority CPUs is acceptable, then the user can enable Intel +SST-BF feature particularly for the above "sched pipe" workload since only two +CPUs are used, they can be scheduled on high priority CPUs and can get boost of +400 MHz. + +Enable Intel(R) SST-BF +~~~~~~~~~~~~~~~~~~~~~~ + +To enable Intel(R) SST-BF feature, execute:: + + # intel-speed-select base-freq enable -a + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + base-freq + enable:success + package-1 + die-0 + cpu-14 + base-freq + enable:success + +In this case, -a option is optional. This not only enables Intel(R) SST-BF, but it +also adjusts the priority of cores using Intel(R) Speed Select Technology Core +Power (Intel(R) SST-CP) features. This option sets the minimum performance of each +Intel(R) Speed Select Technology - Performance Profile (Intel(R) SST-PP) class to +maximum performance so that the hardware will give maximum performance possible +for each CPU. + +If -a option is not used, then the following steps are required before enabling +Intel(R) SST-BF: + +- Discover Intel(R) SST-BF and note low and high priority base frequency +- Note the high prioity CPU list +- Enable CLOS using core-power feature set +- Configure CLOS parameters. Use CLOS.min to set to minimum performance +- Subscribe desired CPUs to CLOS groups + +With this configuration, if the same workload is executed by pinning the +workload to high priority CPUs (CPU 5 and 6 in this case):: + + #taskset -c 5,6 perf bench -r 100 sched pipe + # Running 'sched/pipe' benchmark: + # Executed 1000000 pipe operations between two processes + Total time: 5.627 [sec] + 5.627922 usecs/op + 177685 ops/sec + +This way, by enabling Intel(R) SST-BF, the performance of this benchmark is +improved (latency reduced) by 7.79%. From the turbostat output, it can be +observed that the high priority CPUs reached 3000 MHz compared to 2600 MHz. +The turbostat output:: + + #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1 + Package Core CPU Bzy_MHz + 0 0 0 2151 + 0 1 1 2166 + 0 2 2 2175 + 0 3 3 2175 + 0 4 4 2175 + 0 5 5 3000 + 0 6 6 3000 + 0 7 7 2180 + 0 8 8 2662 + 0 9 9 2176 + 0 10 10 2175 + 0 11 11 2176 + 0 12 12 2176 + 0 13 13 2661 + +Disable Intel(R) SST-BF +~~~~~~~~~~~~~~~~~~~~~~~ + +To disable the Intel(R) SST-BF feature, execute:: + +# intel-speed-select base-freq disable -a + + +Intel(R) Speed Select Technology - Turbo Frequency (Intel(R) SST-TF) +-------------------------------------------------------------------- + +This feature enables the ability to set different "All core turbo ratio limits" +to cores based on the priority. By using this feature, some cores can be +configured to get higher turbo frequency by designating them as high priority at +the cost of lower or no turbo frequency on the low priority cores. + +For this reason, this feature is only useful when system is busy utilizing all +CPUs, but the user wants some configurable option to get high performance on +some CPUs. + +The support of Intel(R) Speed Select Technology - Turbo Frequency (Intel(R) SST-TF) +depends on the Intel(R) Speed Select Technology - Performance Profile (Intel +SST-PP) performance level configuration. It is possible that only a certain +performance level supports Intel(R) SST-TF. It is also possible that only the base +performance level (level = 0) has the support of Intel(R) SST-TF. Hence, first +select the desired performance level to enable this feature. + +In the system under test here, Intel(R) SST-TF is supported at the base +performance level 0, but currently disabled:: + + # intel-speed-select -c 0 perf-profile info -l 0 + Intel(R) Speed Select Technology + package-0 + die-0 + cpu-0 + perf-profile-level-0 + ... + ... + speed-select-turbo-freq:disabled + ... + ... + + +To check if performance can be improved using Intel(R) SST-TF feature, get the turbo +frequency properties with Intel(R) SST-TF enabled and compare to the base turbo +capability of this system. + +Get Base turbo capability +~~~~~~~~~~~~~~~~~~~~~~~~~ + +To get the base turbo capability of performance level 0, execute:: + + # intel-speed-select perf-profile info -l 0 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + perf-profile-level-0 + ... + ... + turbo-ratio-limits-sse + bucket-0 + core-count:2 + max-turbo-frequency(MHz):3200 + bucket-1 + core-count:4 + max-turbo-frequency(MHz):3100 + bucket-2 + core-count:6 + max-turbo-frequency(MHz):3100 + bucket-3 + core-count:8 + max-turbo-frequency(MHz):3100 + bucket-4 + core-count:10 + max-turbo-frequency(MHz):3100 + bucket-5 + core-count:12 + max-turbo-frequency(MHz):3100 + bucket-6 + core-count:14 + max-turbo-frequency(MHz):3100 + bucket-7 + core-count:16 + max-turbo-frequency(MHz):3100 + +Based on the data above, when all the CPUS are busy, the max. frequency of 3100 +MHz can be achieved. If there is some busy workload on cpu 0 - 11 (e.g. stress) +and on CPU 12 and 13, execute "hackbench pipe" workload:: + + # taskset -c 12,13 perf bench -r 100 sched pipe + # Running 'sched/pipe' benchmark: + # Executed 1000000 pipe operations between two processes + Total time: 5.705 [sec] + 5.705488 usecs/op + 175269 ops/sec + +The turbostat output:: + + #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1 + Package Core CPU Bzy_MHz + 0 0 0 3000 + 0 1 1 3000 + 0 2 2 3000 + 0 3 3 3000 + 0 4 4 3000 + 0 5 5 3100 + 0 6 6 3100 + 0 7 7 3000 + 0 8 8 3100 + 0 9 9 3000 + 0 10 10 3000 + 0 11 11 3000 + 0 12 12 3100 + 0 13 13 3100 + +Based on turbostat output, the performance is limited by frequency cap of 3100 +MHz. To check if the hackbench performance can be improved for CPU 12 and CPU +13, first check the capability of the Intel(R) SST-TF feature for this performance +level. + +Get Intel(R) SST-TF Capability +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To get the capability, the "turbo-freq info" command can be used:: + + # intel-speed-select turbo-freq info -l 0 + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-0 + speed-select-turbo-freq + bucket-0 + high-priority-cores-count:2 + high-priority-max-frequency(MHz):3200 + high-priority-max-avx2-frequency(MHz):3200 + high-priority-max-avx512-frequency(MHz):3100 + bucket-1 + high-priority-cores-count:4 + high-priority-max-frequency(MHz):3100 + high-priority-max-avx2-frequency(MHz):3000 + high-priority-max-avx512-frequency(MHz):2900 + bucket-2 + high-priority-cores-count:6 + high-priority-max-frequency(MHz):3100 + high-priority-max-avx2-frequency(MHz):3000 + high-priority-max-avx512-frequency(MHz):2900 + speed-select-turbo-freq-clip-frequencies + low-priority-max-frequency(MHz):2600 + low-priority-max-avx2-frequency(MHz):2400 + low-priority-max-avx512-frequency(MHz):2100 + +Based on the output above, there is an Intel(R) SST-TF bucket for which there are +two high priority cores. If only two high priority cores are set, then max. +turbo frequency on those cores can be increased to 3200 MHz. This is 100 MHz +more than the base turbo capability for all cores. + +In turn, for the hackbench workload, two CPUs can be set as high priority and +rest as low priority. One side effect is that once enabled, the low priority +cores will be clipped to a lower frequency of 2600 MHz. + +Enable Intel(R) SST-TF +~~~~~~~~~~~~~~~~~~~~~~ + +To enable Intel(R) SST-TF, execute:: + + # intel-speed-select -c 12,13 turbo-freq enable -a + Intel(R) Speed Select Technology + Executing on CPU model: X + package-0 + die-0 + cpu-12 + turbo-freq + enable:success + package-0 + die-0 + cpu-13 + turbo-freq + enable:success + package--1 + die-0 + cpu-63 + turbo-freq --auto + enable:success + +In this case, the option "-a" is optional. If set, it enables Intel(R) SST-TF +feature and also sets the CPUs to high and low priority using Intel Speed +Select Technology Core Power (Intel(R) SST-CP) features. The CPU numbers passed +with "-c" arguments are marked as high priority, including its siblings. + +If -a option is not used, then the following steps are required before enabling +Intel(R) SST-TF: + +- Discover Intel(R) SST-TF and note buckets of high priority cores and maximum frequency + +- Enable CLOS using core-power feature set - Configure CLOS parameters + +- Subscribe desired CPUs to CLOS groups making sure that high priority cores are set to the maximum frequency + +If the same hackbench workload is executed, schedule hackbench threads on high +priority CPUs:: + + #taskset -c 12,13 perf bench -r 100 sched pipe + # Running 'sched/pipe' benchmark: + # Executed 1000000 pipe operations between two processes + Total time: 5.510 [sec] + 5.510165 usecs/op + 180826 ops/sec + +This improved performance by around 3.3% improvement on a busy system. Here the +turbostat output will show that the CPU 12 and CPU 13 are getting 100 MHz boost. +The turbostat output:: + + #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1 + Package Core CPU Bzy_MHz + ... + 0 12 12 3200 + 0 13 13 3200 |