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1What: /sys/devices/system/cpu/
2Date: pre-git history
3Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
4Description:
5 A collection of both global and individual CPU attributes
6
7 Individual CPU attributes are contained in subdirectories
8 named by the kernel's logical CPU number, e.g.:
9
10 /sys/devices/system/cpu/cpuX/
11
12What: /sys/devices/system/cpu/kernel_max
13 /sys/devices/system/cpu/offline
14 /sys/devices/system/cpu/online
15 /sys/devices/system/cpu/possible
16 /sys/devices/system/cpu/present
17Date: December 2008
18Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
19Description: CPU topology files that describe kernel limits related to
20 hotplug. Briefly:
21
22 kernel_max: the maximum cpu index allowed by the kernel
23 configuration.
24
25 offline: cpus that are not online because they have been
26 HOTPLUGGED off or exceed the limit of cpus allowed by the
27 kernel configuration (kernel_max above).
28
29 online: cpus that are online and being scheduled.
30
31 possible: cpus that have been allocated resources and can be
32 brought online if they are present.
33
34 present: cpus that have been identified as being present in
35 the system.
36
37 See Documentation/admin-guide/cputopology.rst for more information.
38
39
40What: /sys/devices/system/cpu/probe
41 /sys/devices/system/cpu/release
42Date: November 2009
43Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
44Description: Dynamic addition and removal of CPU's. This is not hotplug
45 removal, this is meant complete removal/addition of the CPU
46 from the system.
47
48 probe: writes to this file will dynamically add a CPU to the
49 system. Information written to the file to add CPU's is
50 architecture specific.
51
52 release: writes to this file dynamically remove a CPU from
53 the system. Information written to the file to remove CPU's
54 is architecture specific.
55
56What: /sys/devices/system/cpu/cpuX/node
57Date: October 2009
58Contact: Linux memory management mailing list <linux-mm@kvack.org>
59Description: Discover NUMA node a CPU belongs to
60
61 When CONFIG_NUMA is enabled, a symbolic link that points
62 to the corresponding NUMA node directory.
63
64 For example, the following symlink is created for cpu42
65 in NUMA node 2:
66
67 /sys/devices/system/cpu/cpu42/node2 -> ../../node/node2
68
69
70What: /sys/devices/system/cpu/cpuX/topology/core_siblings
71 /sys/devices/system/cpu/cpuX/topology/core_siblings_list
72 /sys/devices/system/cpu/cpuX/topology/physical_package_id
73 /sys/devices/system/cpu/cpuX/topology/thread_siblings
74 /sys/devices/system/cpu/cpuX/topology/thread_siblings_list
75 /sys/devices/system/cpu/cpuX/topology/ppin
76Date: December 2008
77Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
78Description: CPU topology files that describe a logical CPU's relationship
79 to other cores and threads in the same physical package.
80
81 One cpuX directory is created per logical CPU in the system,
82 e.g. /sys/devices/system/cpu/cpu42/.
83
84 Briefly, the files above are:
85
86 core_siblings: internal kernel map of cpuX's hardware threads
87 within the same physical_package_id.
88
89 core_siblings_list: human-readable list of the logical CPU
90 numbers within the same physical_package_id as cpuX.
91
92 physical_package_id: physical package id of cpuX. Typically
93 corresponds to a physical socket number, but the actual value
94 is architecture and platform dependent.
95
96 thread_siblings: internal kernel map of cpuX's hardware
97 threads within the same core as cpuX
98
99 thread_siblings_list: human-readable list of cpuX's hardware
100 threads within the same core as cpuX
101
102 ppin: human-readable Protected Processor Identification
103 Number of the socket the cpu# belongs to. There should be
104 one per physical_package_id. File is readable only to
105 admin.
106
107 See Documentation/admin-guide/cputopology.rst for more information.
108
109
110What: /sys/devices/system/cpu/cpuidle/available_governors
111 /sys/devices/system/cpu/cpuidle/current_driver
112 /sys/devices/system/cpu/cpuidle/current_governor
113 /sys/devices/system/cpu/cpuidle/current_governer_ro
114Date: September 2007
115Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
116Description: Discover cpuidle policy and mechanism
117
118 Various CPUs today support multiple idle levels that are
119 differentiated by varying exit latencies and power
120 consumption during idle.
121
122 Idle policy (governor) is differentiated from idle mechanism
123 (driver).
124
125 available_governors: (RO) displays a space separated list of
126 available governors.
127
128 current_driver: (RO) displays current idle mechanism.
129
130 current_governor: (RW) displays current idle policy. Users can
131 switch the governor at runtime by writing to this file.
132
133 current_governor_ro: (RO) displays current idle policy.
134
135 See Documentation/admin-guide/pm/cpuidle.rst and
136 Documentation/driver-api/pm/cpuidle.rst for more information.
137
138
139What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/name
140 /sys/devices/system/cpu/cpuX/cpuidle/stateN/latency
141 /sys/devices/system/cpu/cpuX/cpuidle/stateN/power
142 /sys/devices/system/cpu/cpuX/cpuidle/stateN/time
143 /sys/devices/system/cpu/cpuX/cpuidle/stateN/usage
144 /sys/devices/system/cpu/cpuX/cpuidle/stateN/above
145 /sys/devices/system/cpu/cpuX/cpuidle/stateN/below
146Date: September 2007
147KernelVersion: v2.6.24
148Contact: Linux power management list <linux-pm@vger.kernel.org>
149Description:
150 The directory /sys/devices/system/cpu/cpuX/cpuidle contains per
151 logical CPU specific cpuidle information for each online cpu X.
152 The processor idle states which are available for use have the
153 following attributes:
154
155 ======== ==== =================================================
156 name: (RO) Name of the idle state (string).
157
158 latency: (RO) The latency to exit out of this idle state (in
159 microseconds).
160
161 power: (RO) The power consumed while in this idle state (in
162 milliwatts).
163
164 time: (RO) The total time spent in this idle state
165 (in microseconds).
166
167 usage: (RO) Number of times this state was entered (a count).
168
169 above: (RO) Number of times this state was entered, but the
170 observed CPU idle duration was too short for it
171 (a count).
172
173 below: (RO) Number of times this state was entered, but the
174 observed CPU idle duration was too long for it
175 (a count).
176 ======== ==== =================================================
177
178What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/desc
179Date: February 2008
180KernelVersion: v2.6.25
181Contact: Linux power management list <linux-pm@vger.kernel.org>
182Description:
183 (RO) A small description about the idle state (string).
184
185
186What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/disable
187Date: March 2012
188KernelVersion: v3.10
189Contact: Linux power management list <linux-pm@vger.kernel.org>
190Description:
191 (RW) Option to disable this idle state (bool). The behavior and
192 the effect of the disable variable depends on the implementation
193 of a particular governor. In the ladder governor, for example,
194 it is not coherent, i.e. if one is disabling a light state, then
195 all deeper states are disabled as well, but the disable variable
196 does not reflect it. Likewise, if one enables a deep state but a
197 lighter state still is disabled, then this has no effect.
198
199What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/default_status
200Date: December 2019
201KernelVersion: v5.6
202Contact: Linux power management list <linux-pm@vger.kernel.org>
203Description:
204 (RO) The default status of this state, "enabled" or "disabled".
205
206What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/residency
207Date: March 2014
208KernelVersion: v3.15
209Contact: Linux power management list <linux-pm@vger.kernel.org>
210Description:
211 (RO) Display the target residency i.e. the minimum amount of
212 time (in microseconds) this cpu should spend in this idle state
213 to make the transition worth the effort.
214
215What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/
216Date: March 2018
217KernelVersion: v4.17
218Contact: Linux power management list <linux-pm@vger.kernel.org>
219Description:
220 Idle state usage statistics related to suspend-to-idle.
221
222 This attribute group is only present for states that can be
223 used in suspend-to-idle with suspended timekeeping.
224
225What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/time
226Date: March 2018
227KernelVersion: v4.17
228Contact: Linux power management list <linux-pm@vger.kernel.org>
229Description:
230 Total time spent by the CPU in suspend-to-idle (with scheduler
231 tick suspended) after requesting this state.
232
233What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/usage
234Date: March 2018
235KernelVersion: v4.17
236Contact: Linux power management list <linux-pm@vger.kernel.org>
237Description:
238 Total number of times this state has been requested by the CPU
239 while entering suspend-to-idle.
240
241What: /sys/devices/system/cpu/cpuX/cpufreq/*
242Date: pre-git history
243Contact: linux-pm@vger.kernel.org
244Description: Discover and change clock speed of CPUs
245
246 Clock scaling allows you to change the clock speed of the
247 CPUs on the fly. This is a nice method to save battery
248 power, because the lower the clock speed, the less power
249 the CPU consumes.
250
251 There are many knobs to tweak in this directory.
252
253 See files in Documentation/cpu-freq/ for more information.
254
255
256What: /sys/devices/system/cpu/cpuX/cpufreq/freqdomain_cpus
257Date: June 2013
258Contact: linux-pm@vger.kernel.org
259Description: Discover CPUs in the same CPU frequency coordination domain
260
261 freqdomain_cpus is the list of CPUs (online+offline) that share
262 the same clock/freq domain (possibly at the hardware level).
263 That information may be hidden from the cpufreq core and the
264 value of related_cpus may be different from freqdomain_cpus. This
265 attribute is useful for user space DVFS controllers to get better
266 power/performance results for platforms using acpi-cpufreq.
267
268 This file is only present if the acpi-cpufreq or the cppc-cpufreq
269 drivers are in use.
270
271
272What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
273Date: August 2008
274KernelVersion: 2.6.27
275Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
276Description: Disable L3 cache indices
277
278 These files exist in every CPU's cache/index3 directory. Each
279 cache_disable_{0,1} file corresponds to one disable slot which
280 can be used to disable a cache index. Reading from these files
281 on a processor with this functionality will return the currently
282 disabled index for that node. There is one L3 structure per
283 node, or per internal node on MCM machines. Writing a valid
284 index to one of these files will cause the specified cache
285 index to be disabled.
286
287 All AMD processors with L3 caches provide this functionality.
288 For details, see BKDGs at
289 https://www.amd.com/en/support/tech-docs?keyword=bios+kernel
290
291
292What: /sys/devices/system/cpu/cpufreq/boost
293Date: August 2012
294Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
295Description: Processor frequency boosting control
296
297 This switch controls the boost setting for the whole system.
298 Boosting allows the CPU and the firmware to run at a frequency
299 beyond its nominal limit.
300
301 More details can be found in
302 Documentation/admin-guide/pm/cpufreq.rst
303
304
305What: /sys/devices/system/cpu/cpuX/crash_notes
306 /sys/devices/system/cpu/cpuX/crash_notes_size
307Date: April 2013
308Contact: kexec@lists.infradead.org
309Description: address and size of the percpu note.
310
311 crash_notes: the physical address of the memory that holds the
312 note of cpuX.
313
314 crash_notes_size: size of the note of cpuX.
315
316
317What: /sys/devices/system/cpu/intel_pstate/max_perf_pct
318 /sys/devices/system/cpu/intel_pstate/min_perf_pct
319 /sys/devices/system/cpu/intel_pstate/no_turbo
320Date: February 2013
321Contact: linux-pm@vger.kernel.org
322Description: Parameters for the Intel P-state driver
323
324 Logic for selecting the current P-state in Intel
325 Sandybridge+ processors. The three knobs control
326 limits for the P-state that will be requested by the
327 driver.
328
329 max_perf_pct: limits the maximum P state that will be requested by
330 the driver stated as a percentage of the available performance.
331
332 min_perf_pct: limits the minimum P state that will be requested by
333 the driver stated as a percentage of the available performance.
334
335 no_turbo: limits the driver to selecting P states below the turbo
336 frequency range.
337
338 More details can be found in
339 Documentation/admin-guide/pm/intel_pstate.rst
340
341What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below>
342Date: July 2014(documented, existed before August 2008)
343Contact: Sudeep Holla <sudeep.holla@arm.com>
344 Linux kernel mailing list <linux-kernel@vger.kernel.org>
345Description: Parameters for the CPU cache attributes
346
347 allocation_policy:
348 - WriteAllocate:
349 allocate a memory location to a cache line
350 on a cache miss because of a write
351 - ReadAllocate:
352 allocate a memory location to a cache line
353 on a cache miss because of a read
354 - ReadWriteAllocate:
355 both writeallocate and readallocate
356
357 attributes:
358 LEGACY used only on IA64 and is same as write_policy
359
360 coherency_line_size:
361 the minimum amount of data in bytes that gets
362 transferred from memory to cache
363
364 level:
365 the cache hierarchy in the multi-level cache configuration
366
367 number_of_sets:
368 total number of sets in the cache, a set is a
369 collection of cache lines with the same cache index
370
371 physical_line_partition:
372 number of physical cache line per cache tag
373
374 shared_cpu_list:
375 the list of logical cpus sharing the cache
376
377 shared_cpu_map:
378 logical cpu mask containing the list of cpus sharing
379 the cache
380
381 size:
382 the total cache size in kB
383
384 type:
385 - Instruction: cache that only holds instructions
386 - Data: cache that only caches data
387 - Unified: cache that holds both data and instructions
388
389 ways_of_associativity:
390 degree of freedom in placing a particular block
391 of memory in the cache
392
393 write_policy:
394 - WriteThrough:
395 data is written to both the cache line
396 and to the block in the lower-level memory
397 - WriteBack:
398 data is written only to the cache line and
399 the modified cache line is written to main
400 memory only when it is replaced
401
402
403What: /sys/devices/system/cpu/cpu*/cache/index*/id
404Date: September 2016
405Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
406Description: Cache id
407
408 The id provides a unique number for a specific instance of
409 a cache of a particular type. E.g. there may be a level
410 3 unified cache on each socket in a server and we may
411 assign them ids 0, 1, 2, ...
412
413 Note that id value can be non-contiguous. E.g. level 1
414 caches typically exist per core, but there may not be a
415 power of two cores on a socket, so these caches may be
416 numbered 0, 1, 2, 3, 4, 5, 8, 9, 10, ...
417
418What: /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats
419 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/turbo_stat
420 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/sub_turbo_stat
421 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/unthrottle
422 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/powercap
423 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overtemp
424 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/supply_fault
425 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overcurrent
426 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/occ_reset
427Date: March 2016
428Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
429 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
430Description: POWERNV CPUFreq driver's frequency throttle stats directory and
431 attributes
432
433 'cpuX/cpufreq/throttle_stats' directory contains the CPU frequency
434 throttle stat attributes for the chip. The throttle stats of a cpu
435 is common across all the cpus belonging to a chip. Below are the
436 throttle attributes exported in the 'throttle_stats' directory:
437
438 - turbo_stat : This file gives the total number of times the max
439 frequency is throttled to lower frequency in turbo (at and above
440 nominal frequency) range of frequencies.
441
442 - sub_turbo_stat : This file gives the total number of times the
443 max frequency is throttled to lower frequency in sub-turbo(below
444 nominal frequency) range of frequencies.
445
446 - unthrottle : This file gives the total number of times the max
447 frequency is unthrottled after being throttled.
448
449 - powercap : This file gives the total number of times the max
450 frequency is throttled due to 'Power Capping'.
451
452 - overtemp : This file gives the total number of times the max
453 frequency is throttled due to 'CPU Over Temperature'.
454
455 - supply_fault : This file gives the total number of times the
456 max frequency is throttled due to 'Power Supply Failure'.
457
458 - overcurrent : This file gives the total number of times the
459 max frequency is throttled due to 'Overcurrent'.
460
461 - occ_reset : This file gives the total number of times the max
462 frequency is throttled due to 'OCC Reset'.
463
464 The sysfs attributes representing different throttle reasons like
465 powercap, overtemp, supply_fault, overcurrent and occ_reset map to
466 the reasons provided by OCC firmware for throttling the frequency.
467
468What: /sys/devices/system/cpu/cpufreq/policyX/throttle_stats
469 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/turbo_stat
470 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/sub_turbo_stat
471 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/unthrottle
472 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/powercap
473 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overtemp
474 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/supply_fault
475 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overcurrent
476 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/occ_reset
477Date: March 2016
478Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
479 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
480Description: POWERNV CPUFreq driver's frequency throttle stats directory and
481 attributes
482
483 'policyX/throttle_stats' directory and all the attributes are same as
484 the /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats directory and
485 attributes which give the frequency throttle information of the chip.
486
487What: /sys/devices/system/cpu/cpuX/regs/
488 /sys/devices/system/cpu/cpuX/regs/identification/
489 /sys/devices/system/cpu/cpuX/regs/identification/midr_el1
490 /sys/devices/system/cpu/cpuX/regs/identification/revidr_el1
491 /sys/devices/system/cpu/cpuX/regs/identification/smidr_el1
492Date: June 2016
493Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
494Description: AArch64 CPU registers
495
496 'identification' directory exposes the CPU ID registers for
497 identifying model and revision of the CPU and SMCU.
498
499What: /sys/devices/system/cpu/aarch32_el0
500Date: May 2021
501Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
502Description: Identifies the subset of CPUs in the system that can execute
503 AArch32 (32-bit ARM) applications. If present, the same format as
504 /sys/devices/system/cpu/{offline,online,possible,present} is used.
505 If absent, then all or none of the CPUs can execute AArch32
506 applications and execve() will behave accordingly.
507
508What: /sys/devices/system/cpu/cpuX/cpu_capacity
509Date: December 2016
510Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
511Description: information about CPUs heterogeneity.
512
513 cpu_capacity: capacity of cpuX.
514
515What: /sys/devices/system/cpu/vulnerabilities
516 /sys/devices/system/cpu/vulnerabilities/meltdown
517 /sys/devices/system/cpu/vulnerabilities/spectre_v1
518 /sys/devices/system/cpu/vulnerabilities/spectre_v2
519 /sys/devices/system/cpu/vulnerabilities/spec_store_bypass
520 /sys/devices/system/cpu/vulnerabilities/l1tf
521 /sys/devices/system/cpu/vulnerabilities/mds
522 /sys/devices/system/cpu/vulnerabilities/srbds
523 /sys/devices/system/cpu/vulnerabilities/tsx_async_abort
524 /sys/devices/system/cpu/vulnerabilities/itlb_multihit
525 /sys/devices/system/cpu/vulnerabilities/mmio_stale_data
526 /sys/devices/system/cpu/vulnerabilities/retbleed
527Date: January 2018
528Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
529Description: Information about CPU vulnerabilities
530
531 The files are named after the code names of CPU
532 vulnerabilities. The output of those files reflects the
533 state of the CPUs in the system. Possible output values:
534
535 ================ ==============================================
536 "Not affected" CPU is not affected by the vulnerability
537 "Vulnerable" CPU is affected and no mitigation in effect
538 "Mitigation: $M" CPU is affected and mitigation $M is in effect
539 ================ ==============================================
540
541 See also: Documentation/admin-guide/hw-vuln/index.rst
542
543What: /sys/devices/system/cpu/smt
544 /sys/devices/system/cpu/smt/active
545 /sys/devices/system/cpu/smt/control
546Date: June 2018
547Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
548Description: Control Symmetric Multi Threading (SMT)
549
550 active: Tells whether SMT is active (enabled and siblings online)
551
552 control: Read/write interface to control SMT. Possible
553 values:
554
555 ================ =========================================
556 "on" SMT is enabled
557 "off" SMT is disabled
558 "forceoff" SMT is force disabled. Cannot be changed.
559 "notsupported" SMT is not supported by the CPU
560 "notimplemented" SMT runtime toggling is not
561 implemented for the architecture
562 ================ =========================================
563
564 If control status is "forceoff" or "notsupported" writes
565 are rejected.
566
567What: /sys/devices/system/cpu/cpuX/power/energy_perf_bias
568Date: March 2019
569Contact: linux-pm@vger.kernel.org
570Description: Intel Energy and Performance Bias Hint (EPB)
571
572 EPB for the given CPU in a sliding scale 0 - 15, where a value
573 of 0 corresponds to a hint preference for highest performance
574 and a value of 15 corresponds to the maximum energy savings.
575
576 In order to change the EPB value for the CPU, write either
577 a number in the 0 - 15 sliding scale above, or one of the
578 strings: "performance", "balance-performance", "normal",
579 "balance-power", "power" (that represent values reflected by
580 their meaning), to this attribute.
581
582 This attribute is present for all online CPUs supporting the
583 Intel EPB feature.
584
585What: /sys/devices/system/cpu/umwait_control
586 /sys/devices/system/cpu/umwait_control/enable_c02
587 /sys/devices/system/cpu/umwait_control/max_time
588Date: May 2019
589Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
590Description: Umwait control
591
592 enable_c02: Read/write interface to control umwait C0.2 state
593 Read returns C0.2 state status:
594 0: C0.2 is disabled
595 1: C0.2 is enabled
596
597 Write 'y' or '1' or 'on' to enable C0.2 state.
598 Write 'n' or '0' or 'off' to disable C0.2 state.
599
600 The interface is case insensitive.
601
602 max_time: Read/write interface to control umwait maximum time
603 in TSC-quanta that the CPU can reside in either C0.1
604 or C0.2 state. The time is an unsigned 32-bit number.
605 Note that a value of zero means there is no limit.
606 Low order two bits must be zero.
607
608What: /sys/devices/system/cpu/svm
609Date: August 2019
610Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
611 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
612Description: Secure Virtual Machine
613
614 If 1, it means the system is using the Protected Execution
615 Facility in POWER9 and newer processors. i.e., it is a Secure
616 Virtual Machine.
617
618What: /sys/devices/system/cpu/cpuX/purr
619Date: Apr 2005
620Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
621Description: PURR ticks for this CPU since the system boot.
622
623 The Processor Utilization Resources Register (PURR) is
624 a 64-bit counter which provides an estimate of the
625 resources used by the CPU thread. The contents of this
626 register increases monotonically. This sysfs interface
627 exposes the number of PURR ticks for cpuX.
628
629What: /sys/devices/system/cpu/cpuX/spurr
630Date: Dec 2006
631Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
632Description: SPURR ticks for this CPU since the system boot.
633
634 The Scaled Processor Utilization Resources Register
635 (SPURR) is a 64-bit counter that provides a frequency
636 invariant estimate of the resources used by the CPU
637 thread. The contents of this register increases
638 monotonically. This sysfs interface exposes the number
639 of SPURR ticks for cpuX.
640
641What: /sys/devices/system/cpu/cpuX/idle_purr
642Date: Apr 2020
643Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
644Description: PURR ticks for cpuX when it was idle.
645
646 This sysfs interface exposes the number of PURR ticks
647 for cpuX when it was idle.
648
649What: /sys/devices/system/cpu/cpuX/idle_spurr
650Date: Apr 2020
651Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
652Description: SPURR ticks for cpuX when it was idle.
653
654 This sysfs interface exposes the number of SPURR ticks
655 for cpuX when it was idle.
656
657What: /sys/devices/system/cpu/cpuX/mte_tcf_preferred
658Date: July 2021
659Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
660Description: Preferred MTE tag checking mode
661
662 When a user program specifies more than one MTE tag checking
663 mode, this sysfs node is used to specify which mode should
664 be preferred when scheduling a task on that CPU. Possible
665 values:
666
667 ================ ==============================================
668 "sync" Prefer synchronous mode
669 "asymm" Prefer asymmetric mode
670 "async" Prefer asynchronous mode
671 ================ ==============================================
672
673 See also: Documentation/arm64/memory-tagging-extension.rst
674
675What: /sys/devices/system/cpu/nohz_full
676Date: Apr 2015
677Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
678Description:
679 (RO) the list of CPUs that are in nohz_full mode.
680 These CPUs are set by boot parameter "nohz_full=".
681
682What: /sys/devices/system/cpu/isolated
683Date: Apr 2015
684Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
685Description:
686 (RO) the list of CPUs that are isolated and don't
687 participate in load balancing. These CPUs are set by
688 boot parameter "isolcpus=".
1What: /sys/devices/system/cpu/
2Date: pre-git history
3Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
4Description:
5 A collection of both global and individual CPU attributes
6
7 Individual CPU attributes are contained in subdirectories
8 named by the kernel's logical CPU number, e.g.:
9
10 /sys/devices/system/cpu/cpu#/
11
12What: /sys/devices/system/cpu/kernel_max
13 /sys/devices/system/cpu/offline
14 /sys/devices/system/cpu/online
15 /sys/devices/system/cpu/possible
16 /sys/devices/system/cpu/present
17Date: December 2008
18Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
19Description: CPU topology files that describe kernel limits related to
20 hotplug. Briefly:
21
22 kernel_max: the maximum cpu index allowed by the kernel
23 configuration.
24
25 offline: cpus that are not online because they have been
26 HOTPLUGGED off or exceed the limit of cpus allowed by the
27 kernel configuration (kernel_max above).
28
29 online: cpus that are online and being scheduled.
30
31 possible: cpus that have been allocated resources and can be
32 brought online if they are present.
33
34 present: cpus that have been identified as being present in
35 the system.
36
37 See Documentation/admin-guide/cputopology.rst for more information.
38
39
40What: /sys/devices/system/cpu/probe
41 /sys/devices/system/cpu/release
42Date: November 2009
43Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
44Description: Dynamic addition and removal of CPU's. This is not hotplug
45 removal, this is meant complete removal/addition of the CPU
46 from the system.
47
48 probe: writes to this file will dynamically add a CPU to the
49 system. Information written to the file to add CPU's is
50 architecture specific.
51
52 release: writes to this file dynamically remove a CPU from
53 the system. Information written to the file to remove CPU's
54 is architecture specific.
55
56What: /sys/devices/system/cpu/cpu#/node
57Date: October 2009
58Contact: Linux memory management mailing list <linux-mm@kvack.org>
59Description: Discover NUMA node a CPU belongs to
60
61 When CONFIG_NUMA is enabled, a symbolic link that points
62 to the corresponding NUMA node directory.
63
64 For example, the following symlink is created for cpu42
65 in NUMA node 2:
66
67 /sys/devices/system/cpu/cpu42/node2 -> ../../node/node2
68
69
70What: /sys/devices/system/cpu/cpu#/topology/core_id
71 /sys/devices/system/cpu/cpu#/topology/core_siblings
72 /sys/devices/system/cpu/cpu#/topology/core_siblings_list
73 /sys/devices/system/cpu/cpu#/topology/physical_package_id
74 /sys/devices/system/cpu/cpu#/topology/thread_siblings
75 /sys/devices/system/cpu/cpu#/topology/thread_siblings_list
76Date: December 2008
77Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
78Description: CPU topology files that describe a logical CPU's relationship
79 to other cores and threads in the same physical package.
80
81 One cpu# directory is created per logical CPU in the system,
82 e.g. /sys/devices/system/cpu/cpu42/.
83
84 Briefly, the files above are:
85
86 core_id: the CPU core ID of cpu#. Typically it is the
87 hardware platform's identifier (rather than the kernel's).
88 The actual value is architecture and platform dependent.
89
90 core_siblings: internal kernel map of cpu#'s hardware threads
91 within the same physical_package_id.
92
93 core_siblings_list: human-readable list of the logical CPU
94 numbers within the same physical_package_id as cpu#.
95
96 physical_package_id: physical package id of cpu#. Typically
97 corresponds to a physical socket number, but the actual value
98 is architecture and platform dependent.
99
100 thread_siblings: internal kernel map of cpu#'s hardware
101 threads within the same core as cpu#
102
103 thread_siblings_list: human-readable list of cpu#'s hardware
104 threads within the same core as cpu#
105
106 See Documentation/admin-guide/cputopology.rst for more information.
107
108
109What: /sys/devices/system/cpu/cpuidle/available_governors
110 /sys/devices/system/cpu/cpuidle/current_driver
111 /sys/devices/system/cpu/cpuidle/current_governor
112 /sys/devices/system/cpu/cpuidle/current_governer_ro
113Date: September 2007
114Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
115Description: Discover cpuidle policy and mechanism
116
117 Various CPUs today support multiple idle levels that are
118 differentiated by varying exit latencies and power
119 consumption during idle.
120
121 Idle policy (governor) is differentiated from idle mechanism
122 (driver).
123
124 available_governors: (RO) displays a space separated list of
125 available governors.
126
127 current_driver: (RO) displays current idle mechanism.
128
129 current_governor: (RW) displays current idle policy. Users can
130 switch the governor at runtime by writing to this file.
131
132 current_governor_ro: (RO) displays current idle policy.
133
134 See Documentation/admin-guide/pm/cpuidle.rst and
135 Documentation/driver-api/pm/cpuidle.rst for more information.
136
137
138What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/name
139 /sys/devices/system/cpu/cpuX/cpuidle/stateN/latency
140 /sys/devices/system/cpu/cpuX/cpuidle/stateN/power
141 /sys/devices/system/cpu/cpuX/cpuidle/stateN/time
142 /sys/devices/system/cpu/cpuX/cpuidle/stateN/usage
143 /sys/devices/system/cpu/cpuX/cpuidle/stateN/above
144 /sys/devices/system/cpu/cpuX/cpuidle/stateN/below
145Date: September 2007
146KernelVersion: v2.6.24
147Contact: Linux power management list <linux-pm@vger.kernel.org>
148Description:
149 The directory /sys/devices/system/cpu/cpuX/cpuidle contains per
150 logical CPU specific cpuidle information for each online cpu X.
151 The processor idle states which are available for use have the
152 following attributes:
153
154 ======== ==== =================================================
155 name: (RO) Name of the idle state (string).
156
157 latency: (RO) The latency to exit out of this idle state (in
158 microseconds).
159
160 power: (RO) The power consumed while in this idle state (in
161 milliwatts).
162
163 time: (RO) The total time spent in this idle state
164 (in microseconds).
165
166 usage: (RO) Number of times this state was entered (a count).
167
168 above: (RO) Number of times this state was entered, but the
169 observed CPU idle duration was too short for it
170 (a count).
171
172 below: (RO) Number of times this state was entered, but the
173 observed CPU idle duration was too long for it
174 (a count).
175 ======== ==== =================================================
176
177What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/desc
178Date: February 2008
179KernelVersion: v2.6.25
180Contact: Linux power management list <linux-pm@vger.kernel.org>
181Description:
182 (RO) A small description about the idle state (string).
183
184
185What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/disable
186Date: March 2012
187KernelVersion: v3.10
188Contact: Linux power management list <linux-pm@vger.kernel.org>
189Description:
190 (RW) Option to disable this idle state (bool). The behavior and
191 the effect of the disable variable depends on the implementation
192 of a particular governor. In the ladder governor, for example,
193 it is not coherent, i.e. if one is disabling a light state, then
194 all deeper states are disabled as well, but the disable variable
195 does not reflect it. Likewise, if one enables a deep state but a
196 lighter state still is disabled, then this has no effect.
197
198What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/default_status
199Date: December 2019
200KernelVersion: v5.6
201Contact: Linux power management list <linux-pm@vger.kernel.org>
202Description:
203 (RO) The default status of this state, "enabled" or "disabled".
204
205What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/residency
206Date: March 2014
207KernelVersion: v3.15
208Contact: Linux power management list <linux-pm@vger.kernel.org>
209Description:
210 (RO) Display the target residency i.e. the minimum amount of
211 time (in microseconds) this cpu should spend in this idle state
212 to make the transition worth the effort.
213
214What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/s2idle/
215Date: March 2018
216KernelVersion: v4.17
217Contact: Linux power management list <linux-pm@vger.kernel.org>
218Description:
219 Idle state usage statistics related to suspend-to-idle.
220
221 This attribute group is only present for states that can be
222 used in suspend-to-idle with suspended timekeeping.
223
224What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/s2idle/time
225Date: March 2018
226KernelVersion: v4.17
227Contact: Linux power management list <linux-pm@vger.kernel.org>
228Description:
229 Total time spent by the CPU in suspend-to-idle (with scheduler
230 tick suspended) after requesting this state.
231
232What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/s2idle/usage
233Date: March 2018
234KernelVersion: v4.17
235Contact: Linux power management list <linux-pm@vger.kernel.org>
236Description:
237 Total number of times this state has been requested by the CPU
238 while entering suspend-to-idle.
239
240What: /sys/devices/system/cpu/cpu#/cpufreq/*
241Date: pre-git history
242Contact: linux-pm@vger.kernel.org
243Description: Discover and change clock speed of CPUs
244
245 Clock scaling allows you to change the clock speed of the
246 CPUs on the fly. This is a nice method to save battery
247 power, because the lower the clock speed, the less power
248 the CPU consumes.
249
250 There are many knobs to tweak in this directory.
251
252 See files in Documentation/cpu-freq/ for more information.
253
254
255What: /sys/devices/system/cpu/cpu#/cpufreq/freqdomain_cpus
256Date: June 2013
257Contact: linux-pm@vger.kernel.org
258Description: Discover CPUs in the same CPU frequency coordination domain
259
260 freqdomain_cpus is the list of CPUs (online+offline) that share
261 the same clock/freq domain (possibly at the hardware level).
262 That information may be hidden from the cpufreq core and the
263 value of related_cpus may be different from freqdomain_cpus. This
264 attribute is useful for user space DVFS controllers to get better
265 power/performance results for platforms using acpi-cpufreq.
266
267 This file is only present if the acpi-cpufreq or the cppc-cpufreq
268 drivers are in use.
269
270
271What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
272Date: August 2008
273KernelVersion: 2.6.27
274Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
275Description: Disable L3 cache indices
276
277 These files exist in every CPU's cache/index3 directory. Each
278 cache_disable_{0,1} file corresponds to one disable slot which
279 can be used to disable a cache index. Reading from these files
280 on a processor with this functionality will return the currently
281 disabled index for that node. There is one L3 structure per
282 node, or per internal node on MCM machines. Writing a valid
283 index to one of these files will cause the specified cache
284 index to be disabled.
285
286 All AMD processors with L3 caches provide this functionality.
287 For details, see BKDGs at
288 https://www.amd.com/en/support/tech-docs?keyword=bios+kernel
289
290
291What: /sys/devices/system/cpu/cpufreq/boost
292Date: August 2012
293Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
294Description: Processor frequency boosting control
295
296 This switch controls the boost setting for the whole system.
297 Boosting allows the CPU and the firmware to run at a frequency
298 beyond it's nominal limit.
299
300 More details can be found in
301 Documentation/admin-guide/pm/cpufreq.rst
302
303
304What: /sys/devices/system/cpu/cpu#/crash_notes
305 /sys/devices/system/cpu/cpu#/crash_notes_size
306Date: April 2013
307Contact: kexec@lists.infradead.org
308Description: address and size of the percpu note.
309
310 crash_notes: the physical address of the memory that holds the
311 note of cpu#.
312
313 crash_notes_size: size of the note of cpu#.
314
315
316What: /sys/devices/system/cpu/intel_pstate/max_perf_pct
317 /sys/devices/system/cpu/intel_pstate/min_perf_pct
318 /sys/devices/system/cpu/intel_pstate/no_turbo
319Date: February 2013
320Contact: linux-pm@vger.kernel.org
321Description: Parameters for the Intel P-state driver
322
323 Logic for selecting the current P-state in Intel
324 Sandybridge+ processors. The three knobs control
325 limits for the P-state that will be requested by the
326 driver.
327
328 max_perf_pct: limits the maximum P state that will be requested by
329 the driver stated as a percentage of the available performance.
330
331 min_perf_pct: limits the minimum P state that will be requested by
332 the driver stated as a percentage of the available performance.
333
334 no_turbo: limits the driver to selecting P states below the turbo
335 frequency range.
336
337 More details can be found in
338 Documentation/admin-guide/pm/intel_pstate.rst
339
340What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below>
341Date: July 2014(documented, existed before August 2008)
342Contact: Sudeep Holla <sudeep.holla@arm.com>
343 Linux kernel mailing list <linux-kernel@vger.kernel.org>
344Description: Parameters for the CPU cache attributes
345
346 allocation_policy:
347 - WriteAllocate:
348 allocate a memory location to a cache line
349 on a cache miss because of a write
350 - ReadAllocate:
351 allocate a memory location to a cache line
352 on a cache miss because of a read
353 - ReadWriteAllocate:
354 both writeallocate and readallocate
355
356 attributes:
357 LEGACY used only on IA64 and is same as write_policy
358
359 coherency_line_size:
360 the minimum amount of data in bytes that gets
361 transferred from memory to cache
362
363 level:
364 the cache hierarchy in the multi-level cache configuration
365
366 number_of_sets:
367 total number of sets in the cache, a set is a
368 collection of cache lines with the same cache index
369
370 physical_line_partition:
371 number of physical cache line per cache tag
372
373 shared_cpu_list:
374 the list of logical cpus sharing the cache
375
376 shared_cpu_map:
377 logical cpu mask containing the list of cpus sharing
378 the cache
379
380 size:
381 the total cache size in kB
382
383 type:
384 - Instruction: cache that only holds instructions
385 - Data: cache that only caches data
386 - Unified: cache that holds both data and instructions
387
388 ways_of_associativity:
389 degree of freedom in placing a particular block
390 of memory in the cache
391
392 write_policy:
393 - WriteThrough:
394 data is written to both the cache line
395 and to the block in the lower-level memory
396 - WriteBack:
397 data is written only to the cache line and
398 the modified cache line is written to main
399 memory only when it is replaced
400
401
402What: /sys/devices/system/cpu/cpu*/cache/index*/id
403Date: September 2016
404Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
405Description: Cache id
406
407 The id provides a unique number for a specific instance of
408 a cache of a particular type. E.g. there may be a level
409 3 unified cache on each socket in a server and we may
410 assign them ids 0, 1, 2, ...
411
412 Note that id value can be non-contiguous. E.g. level 1
413 caches typically exist per core, but there may not be a
414 power of two cores on a socket, so these caches may be
415 numbered 0, 1, 2, 3, 4, 5, 8, 9, 10, ...
416
417What: /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats
418 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/turbo_stat
419 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/sub_turbo_stat
420 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/unthrottle
421 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/powercap
422 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overtemp
423 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/supply_fault
424 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overcurrent
425 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/occ_reset
426Date: March 2016
427Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
428 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
429Description: POWERNV CPUFreq driver's frequency throttle stats directory and
430 attributes
431
432 'cpuX/cpufreq/throttle_stats' directory contains the CPU frequency
433 throttle stat attributes for the chip. The throttle stats of a cpu
434 is common across all the cpus belonging to a chip. Below are the
435 throttle attributes exported in the 'throttle_stats' directory:
436
437 - turbo_stat : This file gives the total number of times the max
438 frequency is throttled to lower frequency in turbo (at and above
439 nominal frequency) range of frequencies.
440
441 - sub_turbo_stat : This file gives the total number of times the
442 max frequency is throttled to lower frequency in sub-turbo(below
443 nominal frequency) range of frequencies.
444
445 - unthrottle : This file gives the total number of times the max
446 frequency is unthrottled after being throttled.
447
448 - powercap : This file gives the total number of times the max
449 frequency is throttled due to 'Power Capping'.
450
451 - overtemp : This file gives the total number of times the max
452 frequency is throttled due to 'CPU Over Temperature'.
453
454 - supply_fault : This file gives the total number of times the
455 max frequency is throttled due to 'Power Supply Failure'.
456
457 - overcurrent : This file gives the total number of times the
458 max frequency is throttled due to 'Overcurrent'.
459
460 - occ_reset : This file gives the total number of times the max
461 frequency is throttled due to 'OCC Reset'.
462
463 The sysfs attributes representing different throttle reasons like
464 powercap, overtemp, supply_fault, overcurrent and occ_reset map to
465 the reasons provided by OCC firmware for throttling the frequency.
466
467What: /sys/devices/system/cpu/cpufreq/policyX/throttle_stats
468 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/turbo_stat
469 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/sub_turbo_stat
470 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/unthrottle
471 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/powercap
472 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overtemp
473 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/supply_fault
474 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overcurrent
475 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/occ_reset
476Date: March 2016
477Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
478 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
479Description: POWERNV CPUFreq driver's frequency throttle stats directory and
480 attributes
481
482 'policyX/throttle_stats' directory and all the attributes are same as
483 the /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats directory and
484 attributes which give the frequency throttle information of the chip.
485
486What: /sys/devices/system/cpu/cpuX/regs/
487 /sys/devices/system/cpu/cpuX/regs/identification/
488 /sys/devices/system/cpu/cpuX/regs/identification/midr_el1
489 /sys/devices/system/cpu/cpuX/regs/identification/revidr_el1
490Date: June 2016
491Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
492Description: AArch64 CPU registers
493
494 'identification' directory exposes the CPU ID registers for
495 identifying model and revision of the CPU.
496
497What: /sys/devices/system/cpu/cpu#/cpu_capacity
498Date: December 2016
499Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
500Description: information about CPUs heterogeneity.
501
502 cpu_capacity: capacity of cpu#.
503
504What: /sys/devices/system/cpu/vulnerabilities
505 /sys/devices/system/cpu/vulnerabilities/meltdown
506 /sys/devices/system/cpu/vulnerabilities/spectre_v1
507 /sys/devices/system/cpu/vulnerabilities/spectre_v2
508 /sys/devices/system/cpu/vulnerabilities/spec_store_bypass
509 /sys/devices/system/cpu/vulnerabilities/l1tf
510 /sys/devices/system/cpu/vulnerabilities/mds
511 /sys/devices/system/cpu/vulnerabilities/srbds
512 /sys/devices/system/cpu/vulnerabilities/tsx_async_abort
513 /sys/devices/system/cpu/vulnerabilities/itlb_multihit
514Date: January 2018
515Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
516Description: Information about CPU vulnerabilities
517
518 The files are named after the code names of CPU
519 vulnerabilities. The output of those files reflects the
520 state of the CPUs in the system. Possible output values:
521
522 ================ ==============================================
523 "Not affected" CPU is not affected by the vulnerability
524 "Vulnerable" CPU is affected and no mitigation in effect
525 "Mitigation: $M" CPU is affected and mitigation $M is in effect
526 ================ ==============================================
527
528 See also: Documentation/admin-guide/hw-vuln/index.rst
529
530What: /sys/devices/system/cpu/smt
531 /sys/devices/system/cpu/smt/active
532 /sys/devices/system/cpu/smt/control
533Date: June 2018
534Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
535Description: Control Symmetric Multi Threading (SMT)
536
537 active: Tells whether SMT is active (enabled and siblings online)
538
539 control: Read/write interface to control SMT. Possible
540 values:
541
542 ================ =========================================
543 "on" SMT is enabled
544 "off" SMT is disabled
545 "forceoff" SMT is force disabled. Cannot be changed.
546 "notsupported" SMT is not supported by the CPU
547 "notimplemented" SMT runtime toggling is not
548 implemented for the architecture
549 ================ =========================================
550
551 If control status is "forceoff" or "notsupported" writes
552 are rejected.
553
554What: /sys/devices/system/cpu/cpu#/power/energy_perf_bias
555Date: March 2019
556Contact: linux-pm@vger.kernel.org
557Description: Intel Energy and Performance Bias Hint (EPB)
558
559 EPB for the given CPU in a sliding scale 0 - 15, where a value
560 of 0 corresponds to a hint preference for highest performance
561 and a value of 15 corresponds to the maximum energy savings.
562
563 In order to change the EPB value for the CPU, write either
564 a number in the 0 - 15 sliding scale above, or one of the
565 strings: "performance", "balance-performance", "normal",
566 "balance-power", "power" (that represent values reflected by
567 their meaning), to this attribute.
568
569 This attribute is present for all online CPUs supporting the
570 Intel EPB feature.
571
572What: /sys/devices/system/cpu/umwait_control
573 /sys/devices/system/cpu/umwait_control/enable_c02
574 /sys/devices/system/cpu/umwait_control/max_time
575Date: May 2019
576Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
577Description: Umwait control
578
579 enable_c02: Read/write interface to control umwait C0.2 state
580 Read returns C0.2 state status:
581 0: C0.2 is disabled
582 1: C0.2 is enabled
583
584 Write 'y' or '1' or 'on' to enable C0.2 state.
585 Write 'n' or '0' or 'off' to disable C0.2 state.
586
587 The interface is case insensitive.
588
589 max_time: Read/write interface to control umwait maximum time
590 in TSC-quanta that the CPU can reside in either C0.1
591 or C0.2 state. The time is an unsigned 32-bit number.
592 Note that a value of zero means there is no limit.
593 Low order two bits must be zero.
594
595What: /sys/devices/system/cpu/svm
596Date: August 2019
597Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
598 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
599Description: Secure Virtual Machine
600
601 If 1, it means the system is using the Protected Execution
602 Facility in POWER9 and newer processors. i.e., it is a Secure
603 Virtual Machine.
604
605What: /sys/devices/system/cpu/cpuX/purr
606Date: Apr 2005
607Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
608Description: PURR ticks for this CPU since the system boot.
609
610 The Processor Utilization Resources Register (PURR) is
611 a 64-bit counter which provides an estimate of the
612 resources used by the CPU thread. The contents of this
613 register increases monotonically. This sysfs interface
614 exposes the number of PURR ticks for cpuX.
615
616What: /sys/devices/system/cpu/cpuX/spurr
617Date: Dec 2006
618Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
619Description: SPURR ticks for this CPU since the system boot.
620
621 The Scaled Processor Utilization Resources Register
622 (SPURR) is a 64-bit counter that provides a frequency
623 invariant estimate of the resources used by the CPU
624 thread. The contents of this register increases
625 monotonically. This sysfs interface exposes the number
626 of SPURR ticks for cpuX.
627
628What: /sys/devices/system/cpu/cpuX/idle_purr
629Date: Apr 2020
630Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
631Description: PURR ticks for cpuX when it was idle.
632
633 This sysfs interface exposes the number of PURR ticks
634 for cpuX when it was idle.
635
636What: /sys/devices/system/cpu/cpuX/idle_spurr
637Date: Apr 2020
638Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
639Description: SPURR ticks for cpuX when it was idle.
640
641 This sysfs interface exposes the number of SPURR ticks
642 for cpuX when it was idle.