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/cputopology.txt 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 writtento 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: internel 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/cputopology.txt for more information. 107 108 109What: /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 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 current_driver: (RO) displays current idle mechanism 125 126 current_governor_ro: (RO) displays current idle policy 127 128 With the cpuidle_sysfs_switch boot option enabled (meant for 129 developer testing), the following three attributes are visible 130 instead: 131 132 current_driver: same as described above 133 134 available_governors: (RO) displays a space separated list of 135 available governors 136 137 current_governor: (RW) displays current idle policy. Users can 138 switch the governor at runtime by writing to this file. 139 140 See files in Documentation/cpuidle/ for more information. 141 142 143What: /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 148Date: September 2007 149KernelVersion: v2.6.24 150Contact: Linux power management list <linux-pm@vger.kernel.org> 151Description: 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: 156 157 name: (RO) Name of the idle state (string). 158 159 latency: (RO) The latency to exit out of this idle state (in 160 microseconds). 161 162 power: (RO) The power consumed while in this idle state (in 163 milliwatts). 164 165 time: (RO) The total time spent in this idle state (in microseconds). 166 167 usage: (RO) Number of times this state was entered (a count). 168 169 170What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/desc 171Date: February 2008 172KernelVersion: v2.6.25 173Contact: Linux power management list <linux-pm@vger.kernel.org> 174Description: 175 (RO) A small description about the idle state (string). 176 177 178What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/disable 179Date: March 2012 180KernelVersion: v3.10 181Contact: Linux power management list <linux-pm@vger.kernel.org> 182Description: 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. 190 191 192What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/residency 193Date: March 2014 194KernelVersion: v3.15 195Contact: Linux power management list <linux-pm@vger.kernel.org> 196Description: 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. 200 201 202What: /sys/devices/system/cpu/cpu#/cpufreq/* 203Date: pre-git history 204Contact: linux-pm@vger.kernel.org 205Description: Discover and change clock speed of CPUs 206 207 Clock scaling allows you to change the clock speed of the 208 CPUs on the fly. This is a nice method to save battery 209 power, because the lower the clock speed, the less power 210 the CPU consumes. 211 212 There are many knobs to tweak in this directory. 213 214 See files in Documentation/cpu-freq/ for more information. 215 216 In particular, read Documentation/cpu-freq/user-guide.txt 217 to learn how to control the knobs. 218 219 220What: /sys/devices/system/cpu/cpu#/cpufreq/freqdomain_cpus 221Date: June 2013 222Contact: linux-pm@vger.kernel.org 223Description: Discover CPUs in the same CPU frequency coordination domain 224 225 freqdomain_cpus is the list of CPUs (online+offline) that share 226 the same clock/freq domain (possibly at the hardware level). 227 That information may be hidden from the cpufreq core and the 228 value of related_cpus may be different from freqdomain_cpus. This 229 attribute is useful for user space DVFS controllers to get better 230 power/performance results for platforms using acpi-cpufreq. 231 232 This file is only present if the acpi-cpufreq driver is in use. 233 234 235What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1} 236Date: August 2008 237KernelVersion: 2.6.27 238Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 239Description: Disable L3 cache indices 240 241 These files exist in every CPU's cache/index3 directory. Each 242 cache_disable_{0,1} file corresponds to one disable slot which 243 can be used to disable a cache index. Reading from these files 244 on a processor with this functionality will return the currently 245 disabled index for that node. There is one L3 structure per 246 node, or per internal node on MCM machines. Writing a valid 247 index to one of these files will cause the specificed cache 248 index to be disabled. 249 250 All AMD processors with L3 caches provide this functionality. 251 For details, see BKDGs at 252 http://developer.amd.com/documentation/guides/Pages/default.aspx 253 254 255What: /sys/devices/system/cpu/cpufreq/boost 256Date: August 2012 257Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 258Description: Processor frequency boosting control 259 260 This switch controls the boost setting for the whole system. 261 Boosting allows the CPU and the firmware to run at a frequency 262 beyound it's nominal limit. 263 More details can be found in 264 Documentation/admin-guide/pm/cpufreq.rst 265 266 267What: /sys/devices/system/cpu/cpu#/crash_notes 268 /sys/devices/system/cpu/cpu#/crash_notes_size 269Date: April 2013 270Contact: kexec@lists.infradead.org 271Description: address and size of the percpu note. 272 273 crash_notes: the physical address of the memory that holds the 274 note of cpu#. 275 276 crash_notes_size: size of the note of cpu#. 277 278 279What: /sys/devices/system/cpu/intel_pstate/max_perf_pct 280 /sys/devices/system/cpu/intel_pstate/min_perf_pct 281 /sys/devices/system/cpu/intel_pstate/no_turbo 282Date: February 2013 283Contact: linux-pm@vger.kernel.org 284Description: Parameters for the Intel P-state driver 285 286 Logic for selecting the current P-state in Intel 287 Sandybridge+ processors. The three knobs control 288 limits for the P-state that will be requested by the 289 driver. 290 291 max_perf_pct: limits the maximum P state that will be requested by 292 the driver stated as a percentage of the available performance. 293 294 min_perf_pct: limits the minimum P state that will be requested by 295 the driver stated as a percentage of the available performance. 296 297 no_turbo: limits the driver to selecting P states below the turbo 298 frequency range. 299 300 More details can be found in 301 Documentation/admin-guide/pm/intel_pstate.rst 302 303What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below> 304Date: July 2014(documented, existed before August 2008) 305Contact: Sudeep Holla <sudeep.holla@arm.com> 306 Linux kernel mailing list <linux-kernel@vger.kernel.org> 307Description: Parameters for the CPU cache attributes 308 309 allocation_policy: 310 - WriteAllocate: allocate a memory location to a cache line 311 on a cache miss because of a write 312 - ReadAllocate: allocate a memory location to a cache line 313 on a cache miss because of a read 314 - ReadWriteAllocate: both writeallocate and readallocate 315 316 attributes: LEGACY used only on IA64 and is same as write_policy 317 318 coherency_line_size: the minimum amount of data in bytes that gets 319 transferred from memory to cache 320 321 level: the cache hierarchy in the multi-level cache configuration 322 323 number_of_sets: total number of sets in the cache, a set is a 324 collection of cache lines with the same cache index 325 326 physical_line_partition: number of physical cache line per cache tag 327 328 shared_cpu_list: the list of logical cpus sharing the cache 329 330 shared_cpu_map: logical cpu mask containing the list of cpus sharing 331 the cache 332 333 size: the total cache size in kB 334 335 type: 336 - Instruction: cache that only holds instructions 337 - Data: cache that only caches data 338 - Unified: cache that holds both data and instructions 339 340 ways_of_associativity: degree of freedom in placing a particular block 341 of memory in the cache 342 343 write_policy: 344 - WriteThrough: data is written to both the cache line 345 and to the block in the lower-level memory 346 - WriteBack: data is written only to the cache line and 347 the modified cache line is written to main 348 memory only when it is replaced 349 350 351What: /sys/devices/system/cpu/cpu*/cache/index*/id 352Date: September 2016 353Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 354Description: Cache id 355 356 The id provides a unique number for a specific instance of 357 a cache of a particular type. E.g. there may be a level 358 3 unified cache on each socket in a server and we may 359 assign them ids 0, 1, 2, ... 360 361 Note that id value can be non-contiguous. E.g. level 1 362 caches typically exist per core, but there may not be a 363 power of two cores on a socket, so these caches may be 364 numbered 0, 1, 2, 3, 4, 5, 8, 9, 10, ... 365 366What: /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats 367 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/turbo_stat 368 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/sub_turbo_stat 369 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/unthrottle 370 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/powercap 371 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overtemp 372 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/supply_fault 373 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overcurrent 374 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/occ_reset 375Date: March 2016 376Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 377 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org> 378Description: POWERNV CPUFreq driver's frequency throttle stats directory and 379 attributes 380 381 'cpuX/cpufreq/throttle_stats' directory contains the CPU frequency 382 throttle stat attributes for the chip. The throttle stats of a cpu 383 is common across all the cpus belonging to a chip. Below are the 384 throttle attributes exported in the 'throttle_stats' directory: 385 386 - turbo_stat : This file gives the total number of times the max 387 frequency is throttled to lower frequency in turbo (at and above 388 nominal frequency) range of frequencies. 389 390 - sub_turbo_stat : This file gives the total number of times the 391 max frequency is throttled to lower frequency in sub-turbo(below 392 nominal frequency) range of frequencies. 393 394 - unthrottle : This file gives the total number of times the max 395 frequency is unthrottled after being throttled. 396 397 - powercap : This file gives the total number of times the max 398 frequency is throttled due to 'Power Capping'. 399 400 - overtemp : This file gives the total number of times the max 401 frequency is throttled due to 'CPU Over Temperature'. 402 403 - supply_fault : This file gives the total number of times the 404 max frequency is throttled due to 'Power Supply Failure'. 405 406 - overcurrent : This file gives the total number of times the 407 max frequency is throttled due to 'Overcurrent'. 408 409 - occ_reset : This file gives the total number of times the max 410 frequency is throttled due to 'OCC Reset'. 411 412 The sysfs attributes representing different throttle reasons like 413 powercap, overtemp, supply_fault, overcurrent and occ_reset map to 414 the reasons provided by OCC firmware for throttling the frequency. 415 416What: /sys/devices/system/cpu/cpufreq/policyX/throttle_stats 417 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/turbo_stat 418 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/sub_turbo_stat 419 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/unthrottle 420 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/powercap 421 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overtemp 422 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/supply_fault 423 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overcurrent 424 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/occ_reset 425Date: March 2016 426Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 427 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org> 428Description: POWERNV CPUFreq driver's frequency throttle stats directory and 429 attributes 430 431 'policyX/throttle_stats' directory and all the attributes are same as 432 the /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats directory and 433 attributes which give the frequency throttle information of the chip. 434 435What: /sys/devices/system/cpu/cpuX/regs/ 436 /sys/devices/system/cpu/cpuX/regs/identification/ 437 /sys/devices/system/cpu/cpuX/regs/identification/midr_el1 438 /sys/devices/system/cpu/cpuX/regs/identification/revidr_el1 439Date: June 2016 440Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org> 441Description: AArch64 CPU registers 442 'identification' directory exposes the CPU ID registers for 443 identifying model and revision of the CPU. 444 445What: /sys/devices/system/cpu/cpu#/cpu_capacity 446Date: December 2016 447Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 448Description: information about CPUs heterogeneity. 449 450 cpu_capacity: capacity of cpu#. 451 452What: /sys/devices/system/cpu/vulnerabilities 453 /sys/devices/system/cpu/vulnerabilities/meltdown 454 /sys/devices/system/cpu/vulnerabilities/spectre_v1 455 /sys/devices/system/cpu/vulnerabilities/spectre_v2 456Date: January 2018 457Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 458Description: Information about CPU vulnerabilities 459 460 The files are named after the code names of CPU 461 vulnerabilities. The output of those files reflects the 462 state of the CPUs in the system. Possible output values: 463 464 "Not affected" CPU is not affected by the vulnerability 465 "Vulnerable" CPU is affected and no mitigation in effect 466 "Mitigation: $M" CPU is affected and mitigation $M is in effect 467