1 .. SPDX-License-Identifier: GPL-2.0
3 ============================================================
4 Intel(R) Speed Select Technology User Guide
5 ============================================================
7 The Intel(R) Speed Select Technology (Intel(R) SST) provides a powerful new
8 collection of features that give more granular control over CPU performance.
9 With Intel(R) SST, one server can be configured for power and performance for a
10 variety of diverse workload requirements.
12 Refer to the links below for an overview of the technology:
14 - https://www.intel.com/content/www/us/en/architecture-and-technology/speed-select-technology-article.html
15 - https://builders.intel.com/docs/networkbuilders/intel-speed-select-technology-base-frequency-enhancing-performance.pdf
17 These capabilities are further enhanced in some of the newer generations of
18 server platforms where these features can be enumerated and controlled
19 dynamically without pre-configuring via BIOS setup options. This dynamic
20 configuration is done via mailbox commands to the hardware. One way to enumerate
21 and configure these features is by using the Intel Speed Select utility.
23 This document explains how to use the Intel Speed Select tool to enumerate and
24 control Intel(R) SST features. This document gives example commands and explains
25 how these commands change the power and performance profile of the system under
26 test. Using this tool as an example, customers can replicate the messaging
27 implemented in the tool in their production software.
29 intel-speed-select configuration tool
30 ======================================
32 Most Linux distribution packages may include the "intel-speed-select" tool. If not,
33 it can be built by downloading the Linux kernel tree from kernel.org. Once
34 downloaded, the tool can be built without building the full kernel.
36 From the kernel tree, run the following commands::
38 # cd tools/power/x86/intel-speed-select/
45 To get help with the tool, execute the command below::
47 # intel-speed-select --help
49 The top-level help describes arguments and features. Notice that there is a
50 multi-level help structure in the tool. For example, to get help for the feature "perf-profile"::
52 # intel-speed-select perf-profile --help
54 To get help on a command, another level of help is provided. For example for the command info "info"::
56 # intel-speed-select perf-profile info --help
58 Summary of platform capability
59 ------------------------------
60 To check the current platform and driver capaibilities, execute::
62 #intel-speed-select --info
64 For example on a test system::
66 # intel-speed-select --info
67 Intel(R) Speed Select Technology
68 Executing on CPU model: X
69 Platform: API version : 1
70 Platform: Driver version : 1
71 Platform: mbox supported : 1
72 Platform: mmio supported : 1
73 Intel(R) SST-PP (feature perf-profile) is supported
74 TDP level change control is unlocked, max level: 4
75 Intel(R) SST-TF (feature turbo-freq) is supported
76 Intel(R) SST-BF (feature base-freq) is not supported
77 Intel(R) SST-CP (feature core-power) is supported
79 Intel(R) Speed Select Technology - Performance Profile (Intel(R) SST-PP)
80 ------------------------------------------------------------------------
82 This feature allows configuration of a server dynamically based on workload
83 performance requirements. This helps users during deployment as they do not have
84 to choose a specific server configuration statically. This Intel(R) Speed Select
85 Technology - Performance Profile (Intel(R) SST-PP) feature introduces a mechanism
86 that allows multiple optimized performance profiles per system. Each profile
87 defines a set of CPUs that need to be online and rest offline to sustain a
88 guaranteed base frequency. Once the user issues a command to use a specific
89 performance profile and meet CPU online/offline requirement, the user can expect
90 a change in the base frequency dynamically. This feature is called
91 "perf-profile" when using the Intel Speed Select tool.
93 Number or performance levels
94 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
96 There can be multiple performance profiles on a system. To get the number of
97 profiles, execute the command below::
99 # intel-speed-select perf-profile get-config-levels
100 Intel(R) Speed Select Technology
101 Executing on CPU model: X
111 On this system under test, there are 4 performance profiles in addition to the
112 base performance profile (which is performance level 0).
117 Even if there are multiple performance profiles, it is possible that they
118 are locked. If they are locked, users cannot issue a command to change the
119 performance state. It is possible that there is a BIOS setup to unlock or check
120 with your system vendor.
122 To check if the system is locked, execute the following command::
124 # intel-speed-select perf-profile get-lock-status
125 Intel(R) Speed Select Technology
126 Executing on CPU model: X
136 In this case, lock status is 0, which means that the system is unlocked.
138 Properties of a performance level
139 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
141 To get properties of a specific performance level (For example for the level 0, below), execute the command below::
143 # intel-speed-select perf-profile info -l 0
144 Intel(R) Speed Select Technology
145 Executing on CPU model: X
151 enable-cpu-mask:000003ff,f0003fff
152 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
153 thermal-design-power-ratio:26
154 base-frequency(MHz):2600
155 speed-select-turbo-freq:disabled
156 speed-select-base-freq:disabled
160 Here -l option is used to specify a performance level.
162 If the option -l is omitted, then this command will print information about all
163 the performance levels. The above command is printing properties of the
166 For this performance profile, the list of CPUs displayed by the
167 "enable-cpu-mask/enable-cpu-list" at the max can be "online." When that
168 condition is met, then base frequency of 2600 MHz can be maintained. To
169 understand more, execute "intel-speed-select perf-profile info" for performance
172 # intel-speed-select perf-profile info -l 4
173 Intel(R) Speed Select Technology
174 Executing on CPU model: X
180 enable-cpu-mask:000000fa,f0000faf
181 enable-cpu-list:0,1,2,3,5,7,8,9,10,11,28,29,30,31,33,35,36,37,38,39
182 thermal-design-power-ratio:28
183 base-frequency(MHz):2800
184 speed-select-turbo-freq:disabled
185 speed-select-base-freq:unsupported
189 There are fewer CPUs in the "enable-cpu-mask/enable-cpu-list". Consequently, if
190 the user only keeps these CPUs online and the rest "offline," then the base
191 frequency is increased to 2.8 GHz compared to 2.6 GHz at performance level 0.
193 Get current performance level
194 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
196 To get the current performance level, execute::
198 # intel-speed-select perf-profile get-config-current-level
199 Intel(R) Speed Select Technology
200 Executing on CPU model: X
204 get-config-current_level:0
206 First verify that the base_frequency displayed by the cpufreq sysfs is correct::
208 # cat /sys/devices/system/cpu/cpu0/cpufreq/base_frequency
211 This matches the base-frequency (MHz) field value displayed from the
212 "perf-profile info" command for performance level 0(cpufreq frequency is in
215 To check if the average frequency is equal to the base frequency for a 100% busy
216 workload, disable turbo::
218 # echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo
220 Then runs a busy workload on all CPUs, for example::
224 To verify the base frequency, run turbostat::
226 #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1
228 Package Core CPU Bzy_MHz
238 Changing performance level
239 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
241 To the change the performance level to 4, execute::
243 # intel-speed-select -d perf-profile set-config-level -l 4 -o
244 Intel(R) Speed Select Technology
245 Executing on CPU model: X
250 set_tdp_level:success
252 In the command above, "-o" is optional. If it is specified, then it will also
253 offline CPUs which are not present in the enable_cpu_mask for this performance
256 Now if the base_frequency is checked::
258 #cat /sys/devices/system/cpu/cpu0/cpufreq/base_frequency
261 Which shows that the base frequency now increased from 2600 MHz at performance
262 level 0 to 2800 MHz at performance level 4. As a result, any workload, which can
263 use fewer CPUs, can see a boost of 200 MHz compared to performance level 0.
265 Check presence of other Intel(R) SST features
266 ---------------------------------------------
268 Each of the performance profiles also specifies weather there is support of
269 other two Intel(R) SST features (Intel(R) Speed Select Technology - Base Frequency
270 (Intel(R) SST-BF) and Intel(R) Speed Select Technology - Turbo Frequency (Intel
273 For example, from the output of "perf-profile info" above, for level 0 and level
277 speed-select-turbo-freq:disabled
278 speed-select-base-freq:disabled
281 speed-select-turbo-freq:disabled
282 speed-select-base-freq:unsupported
284 Given these results, the "speed-select-base-freq" (Intel(R) SST-BF) in level 4
285 changed from "disabled" to "unsupported" compared to performance level 0.
287 This means that at performance level 4, the "speed-select-base-freq" feature is
288 not supported. However, at performance level 0, this feature is "supported", but
289 currently "disabled", meaning the user has not activated this feature. Whereas
290 "speed-select-turbo-freq" (Intel(R) SST-TF) is supported at both performance
291 levels, but currently not activated by the user.
293 The Intel(R) SST-BF and the Intel(R) SST-TF features are built on a foundation
294 technology called Intel(R) Speed Select Technology - Core Power (Intel(R) SST-CP).
295 The platform firmware enables this feature when Intel(R) SST-BF or Intel(R) SST-TF
296 is supported on a platform.
298 Intel(R) Speed Select Technology Core Power (Intel(R) SST-CP)
299 ---------------------------------------------------------------
301 Intel(R) Speed Select Technology Core Power (Intel(R) SST-CP) is an interface that
302 allows users to define per core priority. This defines a mechanism to distribute
303 power among cores when there is a power constrained scenario. This defines a
304 class of service (CLOS) configuration.
306 The user can configure up to 4 class of service configurations. Each CLOS group
307 configuration allows definitions of parameters, which affects how the frequency
308 can be limited and power is distributed. Each CPU core can be tied to a class of
309 service and hence an associated priority. The granularity is at core level not
312 Enable CLOS based prioritization
313 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
315 To use CLOS based prioritization feature, firmware must be informed to enable
316 and use a priority type. There is a default per platform priority type, which
317 can be changed with optional command line parameter.
319 To enable and check the options, execute::
321 # intel-speed-select core-power enable --help
322 Intel(R) Speed Select Technology
323 Executing on CPU model: X
324 Enable core-power for a package/die
325 Clos Enable: Specify priority type with [--priority|-p]
326 0: Proportional, 1: Ordered
328 There are two types of priority types:
332 Priority for ordered throttling is defined based on the index of the assigned
333 CLOS group. Where CLOS0 gets highest priority (throttled last).
336 CLOS0 > CLOS1 > CLOS2 > CLOS3.
340 When proportional priority is used, there is an additional parameter called
341 frequency_weight, which can be specified per CLOS group. The goal of
342 proportional priority is to provide each core with the requested min., then
343 distribute all remaining (excess/deficit) budgets in proportion to a defined
344 weight. This proportional priority can be configured using "core-power config"
347 To enable with the platform default priority type, execute::
349 # intel-speed-select core-power enable
350 Intel(R) Speed Select Technology
351 Executing on CPU model: X
363 The scope of this enable is per package or die scoped when a package contains
364 multiple dies. To check if CLOS is enabled and get priority type, "core-power
365 info" command can be used. For example to check the status of core-power feature
368 # intel-speed-select -c 0 core-power info
369 Intel(R) Speed Select Technology
370 Executing on CPU model: X
375 support-status:supported
376 enable-status:enabled
377 clos-enable-status:enabled
378 priority-type:proportional
383 support-status:supported
384 enable-status:enabled
385 clos-enable-status:enabled
386 priority-type:proportional
388 Configuring CLOS groups
389 ~~~~~~~~~~~~~~~~~~~~~~~
391 Each CLOS group has its own attributes including min, max, freq_weight and
392 desired. These parameters can be configured with "core-power config" command.
393 Defaults will be used if user skips setting a parameter except clos id, which is
394 mandatory. To check core-power config options, execute::
396 # intel-speed-select core-power config --help
397 Intel(R) Speed Select Technology
398 Executing on CPU model: X
399 Set core-power configuration for one of the four clos ids
400 Specify targeted clos id with [--clos|-c]
401 Specify clos Proportional Priority [--weight|-w]
402 Specify clos min in MHz with [--min|-n]
403 Specify clos max in MHz with [--max|-m]
407 # intel-speed-select core-power config -c 0
408 Intel(R) Speed Select Technology
409 Executing on CPU model: X
410 clos epp is not specified, default: 0
411 clos frequency weight is not specified, default: 0
412 clos min is not specified, default: 0 MHz
413 clos max is not specified, default: 25500 MHz
414 clos desired is not specified, default: 0
426 The user has the option to change defaults. For example, the user can change the
427 "min" and set the base frequency to always get guaranteed base frequency.
429 Get the current CLOS configuration
430 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
432 To check the current configuration, "core-power get-config" can be used. For
433 example, to get the configuration of CLOS 0::
435 # intel-speed-select core-power get-config -c 0
436 Intel(R) Speed Select Technology
437 Executing on CPU model: X
444 clos-proportional-priority:0
446 clos-max:Max Turbo frequency
454 clos-proportional-priority:0
456 clos-max:Max Turbo frequency
459 Associating a CPU with a CLOS group
460 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
462 To associate a CPU to a CLOS group "core-power assoc" command can be used::
464 # intel-speed-select core-power assoc --help
465 Intel(R) Speed Select Technology
466 Executing on CPU model: X
467 Associate a clos id to a CPU
468 Specify targeted clos id with [--clos|-c]
471 For example to associate CPU 10 to CLOS group 3, execute::
473 # intel-speed-select -c 10 core-power assoc -c 3
474 Intel(R) Speed Select Technology
475 Executing on CPU model: X
482 Once a CPU is associated, its sibling CPUs are also associated to a CLOS group.
483 Once associated, avoid changing Linux "cpufreq" subsystem scaling frequency
486 To check the existing association for a CPU, "core-power get-assoc" command can
487 be used. For example, to get association of CPU 10, execute::
489 # intel-speed-select -c 10 core-power get-assoc
490 Intel(R) Speed Select Technology
491 Executing on CPU model: X
498 This shows that CPU 10 is part of a CLOS group 3.
501 Disable CLOS based prioritization
502 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
504 To disable, execute::
506 # intel-speed-select core-power disable
508 Some features like Intel(R) SST-TF can only be enabled when CLOS based prioritization
509 is enabled. For this reason, disabling while Intel(R) SST-TF is enabled can cause
510 Intel(R) SST-TF to fail. This will cause the "disable" command to display an error
511 if Intel(R) SST-TF is already enabled. In turn, to disable, the Intel(R) SST-TF
512 feature must be disabled first.
514 Intel(R) Speed Select Technology - Base Frequency (Intel(R) SST-BF)
515 -------------------------------------------------------------------
517 The Intel(R) Speed Select Technology - Base Frequency (Intel(R) SST-BF) feature lets
518 the user control base frequency. If some critical workload threads demand
519 constant high guaranteed performance, then this feature can be used to execute
520 the thread at higher base frequency on specific sets of CPUs (high priority
521 CPUs) at the cost of lower base frequency (low priority CPUs) on other CPUs.
522 This feature does not require offline of the low priority CPUs.
524 The support of Intel(R) SST-BF depends on the Intel(R) Speed Select Technology -
525 Performance Profile (Intel(R) SST-PP) performance level configuration. It is
526 possible that only certain performance levels support Intel(R) SST-BF. It is also
527 possible that only base performance level (level = 0) has support of Intel
528 SST-BF. Consequently, first select the desired performance level to enable this
531 In the system under test here, Intel(R) SST-BF is supported at the base
532 performance level 0, but currently disabled. For example for the level 0::
534 # intel-speed-select -c 0 perf-profile info -l 0
535 Intel(R) Speed Select Technology
536 Executing on CPU model: X
543 speed-select-base-freq:disabled
546 Before enabling Intel(R) SST-BF and measuring its impact on a workload
547 performance, execute some workload and measure performance and get a baseline
548 performance to compare against.
550 Here the user wants more guaranteed performance. For this reason, it is likely
551 that turbo is disabled. To disable turbo, execute::
553 #echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo
555 Based on the output of the "intel-speed-select perf-profile info -l 0" base
556 frequency of guaranteed frequency 2600 MHz.
559 Measure baseline performance for comparison
560 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
562 To compare, pick a multi-threaded workload where each thread can be scheduled on
563 separate CPUs. "Hackbench pipe" test is a good example on how to improve
564 performance using Intel(R) SST-BF.
566 Below, the workload is measuring average scheduler wakeup latency, so a lower
567 number means better performance::
569 # taskset -c 3,4 perf bench -r 100 sched pipe
570 # Running 'sched/pipe' benchmark:
571 # Executed 1000000 pipe operations between two processes
572 Total time: 6.102 [sec]
576 While running the above test, if we take turbostat output, it will show us that
577 2 of the CPUs are busy and reaching max. frequency (which would be the base
578 frequency as the turbo is disabled). The turbostat output::
580 #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1
581 Package Core CPU Bzy_MHz
597 From the above turbostat output, both CPU 3 and 4 are very busy and reaching
598 full guaranteed frequency of 2600 MHz.
600 Intel(R) SST-BF Capabilities
601 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
603 To get capabilities of Intel(R) SST-BF for the current performance level 0,
606 # intel-speed-select base-freq info -l 0
607 Intel(R) Speed Select Technology
608 Executing on CPU model: X
612 speed-select-base-freq
613 high-priority-base-frequency(MHz):3000
614 high-priority-cpu-mask:00000216,00002160
615 high-priority-cpu-list:5,6,8,13,33,34,36,41
616 low-priority-base-frequency(MHz):2400
617 tjunction-temperature(C):125
618 thermal-design-power(W):205
620 The above capabilities show that there are some CPUs on this system that can
621 offer base frequency of 3000 MHz compared to the standard base frequency at this
622 performance levels. Nevertheless, these CPUs are fixed, and they are presented
623 via high-priority-cpu-list/high-priority-cpu-mask. But if this Intel(R) SST-BF
624 feature is selected, the low priorities CPUs (which are not in
625 high-priority-cpu-list) can only offer up to 2400 MHz. As a result, if this
626 clipping of low priority CPUs is acceptable, then the user can enable Intel
627 SST-BF feature particularly for the above "sched pipe" workload since only two
628 CPUs are used, they can be scheduled on high priority CPUs and can get boost of
631 Enable Intel(R) SST-BF
632 ~~~~~~~~~~~~~~~~~~~~~~
634 To enable Intel(R) SST-BF feature, execute::
636 # intel-speed-select base-freq enable -a
637 Intel(R) Speed Select Technology
638 Executing on CPU model: X
650 In this case, -a option is optional. This not only enables Intel(R) SST-BF, but it
651 also adjusts the priority of cores using Intel(R) Speed Select Technology Core
652 Power (Intel(R) SST-CP) features. This option sets the minimum performance of each
653 Intel(R) Speed Select Technology - Performance Profile (Intel(R) SST-PP) class to
654 maximum performance so that the hardware will give maximum performance possible
657 If -a option is not used, then the following steps are required before enabling
660 - Discover Intel(R) SST-BF and note low and high priority base frequency
661 - Note the high prioity CPU list
662 - Enable CLOS using core-power feature set
663 - Configure CLOS parameters. Use CLOS.min to set to minimum performance
664 - Subscribe desired CPUs to CLOS groups
666 With this configuration, if the same workload is executed by pinning the
667 workload to high priority CPUs (CPU 5 and 6 in this case)::
669 #taskset -c 5,6 perf bench -r 100 sched pipe
670 # Running 'sched/pipe' benchmark:
671 # Executed 1000000 pipe operations between two processes
672 Total time: 5.627 [sec]
676 This way, by enabling Intel(R) SST-BF, the performance of this benchmark is
677 improved (latency reduced) by 7.79%. From the turbostat output, it can be
678 observed that the high priority CPUs reached 3000 MHz compared to 2600 MHz.
679 The turbostat output::
681 #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1
682 Package Core CPU Bzy_MHz
698 Disable Intel(R) SST-BF
699 ~~~~~~~~~~~~~~~~~~~~~~~
701 To disable the Intel(R) SST-BF feature, execute::
703 # intel-speed-select base-freq disable -a
706 Intel(R) Speed Select Technology - Turbo Frequency (Intel(R) SST-TF)
707 --------------------------------------------------------------------
709 This feature enables the ability to set different "All core turbo ratio limits"
710 to cores based on the priority. By using this feature, some cores can be
711 configured to get higher turbo frequency by designating them as high priority at
712 the cost of lower or no turbo frequency on the low priority cores.
714 For this reason, this feature is only useful when system is busy utilizing all
715 CPUs, but the user wants some configurable option to get high performance on
718 The support of Intel(R) Speed Select Technology - Turbo Frequency (Intel(R) SST-TF)
719 depends on the Intel(R) Speed Select Technology - Performance Profile (Intel
720 SST-PP) performance level configuration. It is possible that only a certain
721 performance level supports Intel(R) SST-TF. It is also possible that only the base
722 performance level (level = 0) has the support of Intel(R) SST-TF. Hence, first
723 select the desired performance level to enable this feature.
725 In the system under test here, Intel(R) SST-TF is supported at the base
726 performance level 0, but currently disabled::
728 # intel-speed-select -c 0 perf-profile info -l 0
729 Intel(R) Speed Select Technology
736 speed-select-turbo-freq:disabled
741 To check if performance can be improved using Intel(R) SST-TF feature, get the turbo
742 frequency properties with Intel(R) SST-TF enabled and compare to the base turbo
743 capability of this system.
745 Get Base turbo capability
746 ~~~~~~~~~~~~~~~~~~~~~~~~~
748 To get the base turbo capability of performance level 0, execute::
750 # intel-speed-select perf-profile info -l 0
751 Intel(R) Speed Select Technology
752 Executing on CPU model: X
759 turbo-ratio-limits-sse
762 max-turbo-frequency(MHz):3200
765 max-turbo-frequency(MHz):3100
768 max-turbo-frequency(MHz):3100
771 max-turbo-frequency(MHz):3100
774 max-turbo-frequency(MHz):3100
777 max-turbo-frequency(MHz):3100
780 max-turbo-frequency(MHz):3100
783 max-turbo-frequency(MHz):3100
785 Based on the data above, when all the CPUS are busy, the max. frequency of 3100
786 MHz can be achieved. If there is some busy workload on cpu 0 - 11 (e.g. stress)
787 and on CPU 12 and 13, execute "hackbench pipe" workload::
789 # taskset -c 12,13 perf bench -r 100 sched pipe
790 # Running 'sched/pipe' benchmark:
791 # Executed 1000000 pipe operations between two processes
792 Total time: 5.705 [sec]
796 The turbostat output::
798 #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1
799 Package Core CPU Bzy_MHz
815 Based on turbostat output, the performance is limited by frequency cap of 3100
816 MHz. To check if the hackbench performance can be improved for CPU 12 and CPU
817 13, first check the capability of the Intel(R) SST-TF feature for this performance
820 Get Intel(R) SST-TF Capability
821 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
823 To get the capability, the "turbo-freq info" command can be used::
825 # intel-speed-select turbo-freq info -l 0
826 Intel(R) Speed Select Technology
827 Executing on CPU model: X
831 speed-select-turbo-freq
833 high-priority-cores-count:2
834 high-priority-max-frequency(MHz):3200
835 high-priority-max-avx2-frequency(MHz):3200
836 high-priority-max-avx512-frequency(MHz):3100
838 high-priority-cores-count:4
839 high-priority-max-frequency(MHz):3100
840 high-priority-max-avx2-frequency(MHz):3000
841 high-priority-max-avx512-frequency(MHz):2900
843 high-priority-cores-count:6
844 high-priority-max-frequency(MHz):3100
845 high-priority-max-avx2-frequency(MHz):3000
846 high-priority-max-avx512-frequency(MHz):2900
847 speed-select-turbo-freq-clip-frequencies
848 low-priority-max-frequency(MHz):2600
849 low-priority-max-avx2-frequency(MHz):2400
850 low-priority-max-avx512-frequency(MHz):2100
852 Based on the output above, there is an Intel(R) SST-TF bucket for which there are
853 two high priority cores. If only two high priority cores are set, then max.
854 turbo frequency on those cores can be increased to 3200 MHz. This is 100 MHz
855 more than the base turbo capability for all cores.
857 In turn, for the hackbench workload, two CPUs can be set as high priority and
858 rest as low priority. One side effect is that once enabled, the low priority
859 cores will be clipped to a lower frequency of 2600 MHz.
861 Enable Intel(R) SST-TF
862 ~~~~~~~~~~~~~~~~~~~~~~
864 To enable Intel(R) SST-TF, execute::
866 # intel-speed-select -c 12,13 turbo-freq enable -a
867 Intel(R) Speed Select Technology
868 Executing on CPU model: X
885 In this case, the option "-a" is optional. If set, it enables Intel(R) SST-TF
886 feature and also sets the CPUs to high and low priority using Intel Speed
887 Select Technology Core Power (Intel(R) SST-CP) features. The CPU numbers passed
888 with "-c" arguments are marked as high priority, including its siblings.
890 If -a option is not used, then the following steps are required before enabling
893 - Discover Intel(R) SST-TF and note buckets of high priority cores and maximum frequency
895 - Enable CLOS using core-power feature set - Configure CLOS parameters
897 - Subscribe desired CPUs to CLOS groups making sure that high priority cores are set to the maximum frequency
899 If the same hackbench workload is executed, schedule hackbench threads on high
902 #taskset -c 12,13 perf bench -r 100 sched pipe
903 # Running 'sched/pipe' benchmark:
904 # Executed 1000000 pipe operations between two processes
905 Total time: 5.510 [sec]
909 This improved performance by around 3.3% improvement on a busy system. Here the
910 turbostat output will show that the CPU 12 and CPU 13 are getting 100 MHz boost.
911 The turbostat output::
913 #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1
914 Package Core CPU Bzy_MHz