1 What: /sys/devices/system/cpu/
3 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
5 A collection of both global and individual CPU attributes
7 Individual CPU attributes are contained in subdirectories
8 named by the kernel's logical CPU number, e.g.:
10 /sys/devices/system/cpu/cpu#/
12 What: /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
18 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
19 Description: CPU topology files that describe kernel limits related to
22 kernel_max: the maximum cpu index allowed by the kernel
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).
29 online: cpus that are online and being scheduled.
31 possible: cpus that have been allocated resources and can be
32 brought online if they are present.
34 present: cpus that have been identified as being present in
37 See Documentation/cputopology.txt for more information.
40 What: /sys/devices/system/cpu/probe
41 /sys/devices/system/cpu/release
43 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
44 Description: Dynamic addition and removal of CPU's. This is not hotplug
45 removal, this is meant complete removal/addition of the CPU
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.
52 release: writes to this file dynamically remove a CPU from
53 the system. Information writtento the file to remove CPU's
54 is architecture specific.
56 What: /sys/devices/system/cpu/cpu#/node
58 Contact: Linux memory management mailing list <linux-mm@kvack.org>
59 Description: Discover NUMA node a CPU belongs to
61 When CONFIG_NUMA is enabled, a symbolic link that points
62 to the corresponding NUMA node directory.
64 For example, the following symlink is created for cpu42
67 /sys/devices/system/cpu/cpu42/node2 -> ../../node/node2
70 What: /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
77 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
78 Description: CPU topology files that describe a logical CPU's relationship
79 to other cores and threads in the same physical package.
81 One cpu# directory is created per logical CPU in the system,
82 e.g. /sys/devices/system/cpu/cpu42/.
84 Briefly, the files above are:
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.
90 core_siblings: internal kernel map of cpu#'s hardware threads
91 within the same physical_package_id.
93 core_siblings_list: human-readable list of the logical CPU
94 numbers within the same physical_package_id as cpu#.
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.
100 thread_siblings: internel kernel map of cpu#'s hardware
101 threads within the same core as cpu#
103 thread_siblings_list: human-readable list of cpu#'s hardware
104 threads within the same core as cpu#
106 See Documentation/cputopology.txt for more information.
109 What: /sys/devices/system/cpu/cpuidle/current_driver
110 /sys/devices/system/cpu/cpuidle/current_governer_ro
111 /sys/devices/system/cpu/cpuidle/available_governors
112 /sys/devices/system/cpu/cpuidle/current_governor
114 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
115 Description: Discover cpuidle policy and mechanism
117 Various CPUs today support multiple idle levels that are
118 differentiated by varying exit latencies and power
119 consumption during idle.
121 Idle policy (governor) is differentiated from idle mechanism
124 current_driver: (RO) displays current idle mechanism
126 current_governor_ro: (RO) displays current idle policy
128 With the cpuidle_sysfs_switch boot option enabled (meant for
129 developer testing), the following three attributes are visible
132 current_driver: same as described above
134 available_governors: (RO) displays a space separated list of
137 current_governor: (RW) displays current idle policy. Users can
138 switch the governor at runtime by writing to this file.
140 See files in Documentation/cpuidle/ for more information.
143 What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/name
144 /sys/devices/system/cpu/cpuX/cpuidle/stateN/latency
145 /sys/devices/system/cpu/cpuX/cpuidle/stateN/power
146 /sys/devices/system/cpu/cpuX/cpuidle/stateN/time
147 /sys/devices/system/cpu/cpuX/cpuidle/stateN/usage
149 KernelVersion: v2.6.24
150 Contact: Linux power management list <linux-pm@vger.kernel.org>
152 The directory /sys/devices/system/cpu/cpuX/cpuidle contains per
153 logical CPU specific cpuidle information for each online cpu X.
154 The processor idle states which are available for use have the
155 following attributes:
157 name: (RO) Name of the idle state (string).
159 latency: (RO) The latency to exit out of this idle state (in
162 power: (RO) The power consumed while in this idle state (in
165 time: (RO) The total time spent in this idle state (in microseconds).
167 usage: (RO) Number of times this state was entered (a count).
170 What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/desc
172 KernelVersion: v2.6.25
173 Contact: Linux power management list <linux-pm@vger.kernel.org>
175 (RO) A small description about the idle state (string).
178 What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/disable
181 Contact: Linux power management list <linux-pm@vger.kernel.org>
183 (RW) Option to disable this idle state (bool). The behavior and
184 the effect of the disable variable depends on the implementation
185 of a particular governor. In the ladder governor, for example,
186 it is not coherent, i.e. if one is disabling a light state, then
187 all deeper states are disabled as well, but the disable variable
188 does not reflect it. Likewise, if one enables a deep state but a
189 lighter state still is disabled, then this has no effect.
192 What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/residency
195 Contact: Linux power management list <linux-pm@vger.kernel.org>
197 (RO) Display the target residency i.e. the minimum amount of
198 time (in microseconds) this cpu should spend in this idle state
199 to make the transition worth the effort.
201 What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/s2idle/
204 Contact: Linux power management list <linux-pm@vger.kernel.org>
206 Idle state usage statistics related to suspend-to-idle.
208 This attribute group is only present for states that can be
209 used in suspend-to-idle with suspended timekeeping.
211 What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/s2idle/time
214 Contact: Linux power management list <linux-pm@vger.kernel.org>
216 Total time spent by the CPU in suspend-to-idle (with scheduler
217 tick suspended) after requesting this state.
219 What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/s2idle/usage
222 Contact: Linux power management list <linux-pm@vger.kernel.org>
224 Total number of times this state has been requested by the CPU
225 while entering suspend-to-idle.
227 What: /sys/devices/system/cpu/cpu#/cpufreq/*
228 Date: pre-git history
229 Contact: linux-pm@vger.kernel.org
230 Description: Discover and change clock speed of CPUs
232 Clock scaling allows you to change the clock speed of the
233 CPUs on the fly. This is a nice method to save battery
234 power, because the lower the clock speed, the less power
237 There are many knobs to tweak in this directory.
239 See files in Documentation/cpu-freq/ for more information.
242 What: /sys/devices/system/cpu/cpu#/cpufreq/freqdomain_cpus
244 Contact: linux-pm@vger.kernel.org
245 Description: Discover CPUs in the same CPU frequency coordination domain
247 freqdomain_cpus is the list of CPUs (online+offline) that share
248 the same clock/freq domain (possibly at the hardware level).
249 That information may be hidden from the cpufreq core and the
250 value of related_cpus may be different from freqdomain_cpus. This
251 attribute is useful for user space DVFS controllers to get better
252 power/performance results for platforms using acpi-cpufreq.
254 This file is only present if the acpi-cpufreq driver is in use.
257 What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
259 KernelVersion: 2.6.27
260 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
261 Description: Disable L3 cache indices
263 These files exist in every CPU's cache/index3 directory. Each
264 cache_disable_{0,1} file corresponds to one disable slot which
265 can be used to disable a cache index. Reading from these files
266 on a processor with this functionality will return the currently
267 disabled index for that node. There is one L3 structure per
268 node, or per internal node on MCM machines. Writing a valid
269 index to one of these files will cause the specificed cache
270 index to be disabled.
272 All AMD processors with L3 caches provide this functionality.
273 For details, see BKDGs at
274 http://developer.amd.com/documentation/guides/Pages/default.aspx
277 What: /sys/devices/system/cpu/cpufreq/boost
279 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
280 Description: Processor frequency boosting control
282 This switch controls the boost setting for the whole system.
283 Boosting allows the CPU and the firmware to run at a frequency
284 beyound it's nominal limit.
285 More details can be found in
286 Documentation/admin-guide/pm/cpufreq.rst
289 What: /sys/devices/system/cpu/cpu#/crash_notes
290 /sys/devices/system/cpu/cpu#/crash_notes_size
292 Contact: kexec@lists.infradead.org
293 Description: address and size of the percpu note.
295 crash_notes: the physical address of the memory that holds the
298 crash_notes_size: size of the note of cpu#.
301 What: /sys/devices/system/cpu/intel_pstate/max_perf_pct
302 /sys/devices/system/cpu/intel_pstate/min_perf_pct
303 /sys/devices/system/cpu/intel_pstate/no_turbo
305 Contact: linux-pm@vger.kernel.org
306 Description: Parameters for the Intel P-state driver
308 Logic for selecting the current P-state in Intel
309 Sandybridge+ processors. The three knobs control
310 limits for the P-state that will be requested by the
313 max_perf_pct: limits the maximum P state that will be requested by
314 the driver stated as a percentage of the available performance.
316 min_perf_pct: limits the minimum P state that will be requested by
317 the driver stated as a percentage of the available performance.
319 no_turbo: limits the driver to selecting P states below the turbo
322 More details can be found in
323 Documentation/admin-guide/pm/intel_pstate.rst
325 What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below>
326 Date: July 2014(documented, existed before August 2008)
327 Contact: Sudeep Holla <sudeep.holla@arm.com>
328 Linux kernel mailing list <linux-kernel@vger.kernel.org>
329 Description: Parameters for the CPU cache attributes
332 - WriteAllocate: allocate a memory location to a cache line
333 on a cache miss because of a write
334 - ReadAllocate: allocate a memory location to a cache line
335 on a cache miss because of a read
336 - ReadWriteAllocate: both writeallocate and readallocate
338 attributes: LEGACY used only on IA64 and is same as write_policy
340 coherency_line_size: the minimum amount of data in bytes that gets
341 transferred from memory to cache
343 level: the cache hierarchy in the multi-level cache configuration
345 number_of_sets: total number of sets in the cache, a set is a
346 collection of cache lines with the same cache index
348 physical_line_partition: number of physical cache line per cache tag
350 shared_cpu_list: the list of logical cpus sharing the cache
352 shared_cpu_map: logical cpu mask containing the list of cpus sharing
355 size: the total cache size in kB
358 - Instruction: cache that only holds instructions
359 - Data: cache that only caches data
360 - Unified: cache that holds both data and instructions
362 ways_of_associativity: degree of freedom in placing a particular block
363 of memory in the cache
366 - WriteThrough: data is written to both the cache line
367 and to the block in the lower-level memory
368 - WriteBack: data is written only to the cache line and
369 the modified cache line is written to main
370 memory only when it is replaced
373 What: /sys/devices/system/cpu/cpu*/cache/index*/id
375 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
376 Description: Cache id
378 The id provides a unique number for a specific instance of
379 a cache of a particular type. E.g. there may be a level
380 3 unified cache on each socket in a server and we may
381 assign them ids 0, 1, 2, ...
383 Note that id value can be non-contiguous. E.g. level 1
384 caches typically exist per core, but there may not be a
385 power of two cores on a socket, so these caches may be
386 numbered 0, 1, 2, 3, 4, 5, 8, 9, 10, ...
388 What: /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats
389 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/turbo_stat
390 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/sub_turbo_stat
391 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/unthrottle
392 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/powercap
393 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overtemp
394 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/supply_fault
395 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overcurrent
396 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/occ_reset
398 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
399 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
400 Description: POWERNV CPUFreq driver's frequency throttle stats directory and
403 'cpuX/cpufreq/throttle_stats' directory contains the CPU frequency
404 throttle stat attributes for the chip. The throttle stats of a cpu
405 is common across all the cpus belonging to a chip. Below are the
406 throttle attributes exported in the 'throttle_stats' directory:
408 - turbo_stat : This file gives the total number of times the max
409 frequency is throttled to lower frequency in turbo (at and above
410 nominal frequency) range of frequencies.
412 - sub_turbo_stat : This file gives the total number of times the
413 max frequency is throttled to lower frequency in sub-turbo(below
414 nominal frequency) range of frequencies.
416 - unthrottle : This file gives the total number of times the max
417 frequency is unthrottled after being throttled.
419 - powercap : This file gives the total number of times the max
420 frequency is throttled due to 'Power Capping'.
422 - overtemp : This file gives the total number of times the max
423 frequency is throttled due to 'CPU Over Temperature'.
425 - supply_fault : This file gives the total number of times the
426 max frequency is throttled due to 'Power Supply Failure'.
428 - overcurrent : This file gives the total number of times the
429 max frequency is throttled due to 'Overcurrent'.
431 - occ_reset : This file gives the total number of times the max
432 frequency is throttled due to 'OCC Reset'.
434 The sysfs attributes representing different throttle reasons like
435 powercap, overtemp, supply_fault, overcurrent and occ_reset map to
436 the reasons provided by OCC firmware for throttling the frequency.
438 What: /sys/devices/system/cpu/cpufreq/policyX/throttle_stats
439 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/turbo_stat
440 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/sub_turbo_stat
441 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/unthrottle
442 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/powercap
443 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overtemp
444 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/supply_fault
445 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overcurrent
446 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/occ_reset
448 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
449 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
450 Description: POWERNV CPUFreq driver's frequency throttle stats directory and
453 'policyX/throttle_stats' directory and all the attributes are same as
454 the /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats directory and
455 attributes which give the frequency throttle information of the chip.
457 What: /sys/devices/system/cpu/cpuX/regs/
458 /sys/devices/system/cpu/cpuX/regs/identification/
459 /sys/devices/system/cpu/cpuX/regs/identification/midr_el1
460 /sys/devices/system/cpu/cpuX/regs/identification/revidr_el1
462 Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
463 Description: AArch64 CPU registers
464 'identification' directory exposes the CPU ID registers for
465 identifying model and revision of the CPU.
467 What: /sys/devices/system/cpu/cpu#/cpu_capacity
469 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
470 Description: information about CPUs heterogeneity.
472 cpu_capacity: capacity of cpu#.
474 What: /sys/devices/system/cpu/vulnerabilities
475 /sys/devices/system/cpu/vulnerabilities/meltdown
476 /sys/devices/system/cpu/vulnerabilities/spectre_v1
477 /sys/devices/system/cpu/vulnerabilities/spectre_v2
478 /sys/devices/system/cpu/vulnerabilities/spec_store_bypass
479 /sys/devices/system/cpu/vulnerabilities/l1tf
480 /sys/devices/system/cpu/vulnerabilities/mds
481 /sys/devices/system/cpu/vulnerabilities/srbds
482 /sys/devices/system/cpu/vulnerabilities/tsx_async_abort
483 /sys/devices/system/cpu/vulnerabilities/itlb_multihit
485 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
486 Description: Information about CPU vulnerabilities
488 The files are named after the code names of CPU
489 vulnerabilities. The output of those files reflects the
490 state of the CPUs in the system. Possible output values:
492 "Not affected" CPU is not affected by the vulnerability
493 "Vulnerable" CPU is affected and no mitigation in effect
494 "Mitigation: $M" CPU is affected and mitigation $M is in effect
496 See also: Documentation/admin-guide/hw-vuln/index.rst
498 What: /sys/devices/system/cpu/smt
499 /sys/devices/system/cpu/smt/active
500 /sys/devices/system/cpu/smt/control
502 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
503 Description: Control Symetric Multi Threading (SMT)
505 active: Tells whether SMT is active (enabled and siblings online)
507 control: Read/write interface to control SMT. Possible
511 "off" SMT is disabled
512 "forceoff" SMT is force disabled. Cannot be changed.
513 "notsupported" SMT is not supported by the CPU
515 If control status is "forceoff" or "notsupported" writes