Documentation/ABI/testing/sysfs-devices-system-cpu

   1 What:           /sys/devices/system/cpu/
   2 Date:           pre-git history
   3 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
   4 Description:
   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
  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
  17 Date:           December 2008
  18 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
  19 Description:    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
  40 What:           /sys/devices/system/cpu/probe
  41                 /sys/devices/system/cpu/release
  42 Date:           November 2009
  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
  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
  56 What:           /sys/devices/system/cpu/cpu#/node
  57 Date:           October 2009
  58 Contact:        Linux memory management mailing list <linux-mm@kvack.org>
  59 Description:    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
  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
  76 Date:           December 2008
  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.
  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/admin-guide/cputopology.rst for more information.
 107
 108
 109 What:           /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
 113 Date:           September 2007
 114 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
 115 Description:    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
 138 What:           /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
 145 Date:           September 2007
 146 KernelVersion:  v2.6.24
 147 Contact:        Linux power management list <linux-pm@vger.kernel.org>
 148 Description:
 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
 177 What:           /sys/devices/system/cpu/cpuX/cpuidle/stateN/desc
 178 Date:           February 2008
 179 KernelVersion:  v2.6.25
 180 Contact:        Linux power management list <linux-pm@vger.kernel.org>
 181 Description:
 182                 (RO) A small description about the idle state (string).
 183
 184
 185 What:           /sys/devices/system/cpu/cpuX/cpuidle/stateN/disable
 186 Date:           March 2012
 187 KernelVersion:  v3.10
 188 Contact:        Linux power management list <linux-pm@vger.kernel.org>
 189 Description:
 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
 198 What:           /sys/devices/system/cpu/cpuX/cpuidle/stateN/default_status
 199 Date:           December 2019
 200 KernelVersion:  v5.6
 201 Contact:        Linux power management list <linux-pm@vger.kernel.org>
 202 Description:
 203                 (RO) The default status of this state, "enabled" or "disabled".
 204
 205 What:           /sys/devices/system/cpu/cpuX/cpuidle/stateN/residency
 206 Date:           March 2014
 207 KernelVersion:  v3.15
 208 Contact:        Linux power management list <linux-pm@vger.kernel.org>
 209 Description:
 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
 214 What:           /sys/devices/system/cpu/cpuX/cpuidle/stateN/s2idle/
 215 Date:           March 2018
 216 KernelVersion:  v4.17
 217 Contact:        Linux power management list <linux-pm@vger.kernel.org>
 218 Description:
 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
 224 What:           /sys/devices/system/cpu/cpuX/cpuidle/stateN/s2idle/time
 225 Date:           March 2018
 226 KernelVersion:  v4.17
 227 Contact:        Linux power management list <linux-pm@vger.kernel.org>
 228 Description:
 229                 Total time spent by the CPU in suspend-to-idle (with scheduler
 230                 tick suspended) after requesting this state.
 231
 232 What:           /sys/devices/system/cpu/cpuX/cpuidle/stateN/s2idle/usage
 233 Date:           March 2018
 234 KernelVersion:  v4.17
 235 Contact:        Linux power management list <linux-pm@vger.kernel.org>
 236 Description:
 237                 Total number of times this state has been requested by the CPU
 238                 while entering suspend-to-idle.
 239
 240 What:           /sys/devices/system/cpu/cpu#/cpufreq/*
 241 Date:           pre-git history
 242 Contact:        linux-pm@vger.kernel.org
 243 Description:    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
 255 What:           /sys/devices/system/cpu/cpu#/cpufreq/freqdomain_cpus
 256 Date:           June 2013
 257 Contact:        linux-pm@vger.kernel.org
 258 Description:    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 driver is in use.
 268
 269
 270 What:           /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
 271 Date:           August 2008
 272 KernelVersion:  2.6.27
 273 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
 274 Description:    Disable L3 cache indices
 275
 276                 These files exist in every CPU's cache/index3 directory. Each
 277                 cache_disable_{0,1} file corresponds to one disable slot which
 278                 can be used to disable a cache index. Reading from these files
 279                 on a processor with this functionality will return the currently
 280                 disabled index for that node. There is one L3 structure per
 281                 node, or per internal node on MCM machines. Writing a valid
 282                 index to one of these files will cause the specificed cache
 283                 index to be disabled.
 284
 285                 All AMD processors with L3 caches provide this functionality.
 286                 For details, see BKDGs at
 287                 http://developer.amd.com/documentation/guides/Pages/default.aspx
 288
 289
 290 What:           /sys/devices/system/cpu/cpufreq/boost
 291 Date:           August 2012
 292 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
 293 Description:    Processor frequency boosting control
 294
 295                 This switch controls the boost setting for the whole system.
 296                 Boosting allows the CPU and the firmware to run at a frequency
 297                 beyound it's nominal limit.
 298
 299                 More details can be found in
 300                 Documentation/admin-guide/pm/cpufreq.rst
 301
 302
 303 What:           /sys/devices/system/cpu/cpu#/crash_notes
 304                 /sys/devices/system/cpu/cpu#/crash_notes_size
 305 Date:           April 2013
 306 Contact:        kexec@lists.infradead.org
 307 Description:    address and size of the percpu note.
 308
 309                 crash_notes: the physical address of the memory that holds the
 310                 note of cpu#.
 311
 312                 crash_notes_size: size of the note of cpu#.
 313
 314
 315 What:           /sys/devices/system/cpu/intel_pstate/max_perf_pct
 316                 /sys/devices/system/cpu/intel_pstate/min_perf_pct
 317                 /sys/devices/system/cpu/intel_pstate/no_turbo
 318 Date:           February 2013
 319 Contact:        linux-pm@vger.kernel.org
 320 Description:    Parameters for the Intel P-state driver
 321
 322                 Logic for selecting the current P-state in Intel
 323                 Sandybridge+ processors. The three knobs control
 324                 limits for the P-state that will be requested by the
 325                 driver.
 326
 327                 max_perf_pct: limits the maximum P state that will be requested by
 328                 the driver stated as a percentage of the available performance.
 329
 330                 min_perf_pct: limits the minimum P state that will be requested by
 331                 the driver stated as a percentage of the available performance.
 332
 333                 no_turbo: limits the driver to selecting P states below the turbo
 334                 frequency range.
 335
 336                 More details can be found in
 337                 Documentation/admin-guide/pm/intel_pstate.rst
 338
 339 What:           /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below>
 340 Date:           July 2014(documented, existed before August 2008)
 341 Contact:        Sudeep Holla <sudeep.holla@arm.com>
 342                 Linux kernel mailing list <linux-kernel@vger.kernel.org>
 343 Description:    Parameters for the CPU cache attributes
 344
 345                 allocation_policy:
 346                         - WriteAllocate:
 347                                         allocate a memory location to a cache line
 348                                         on a cache miss because of a write
 349                         - ReadAllocate:
 350                                         allocate a memory location to a cache line
 351                                         on a cache miss because of a read
 352                         - ReadWriteAllocate:
 353                                         both writeallocate and readallocate
 354
 355                 attributes:
 356                             LEGACY used only on IA64 and is same as write_policy
 357
 358                 coherency_line_size:
 359                                      the minimum amount of data in bytes that gets
 360                                      transferred from memory to cache
 361
 362                 level:
 363                         the cache hierarchy in the multi-level cache configuration
 364
 365                 number_of_sets:
 366                                 total number of sets in the cache, a set is a
 367                                 collection of cache lines with the same cache index
 368
 369                 physical_line_partition:
 370                                 number of physical cache line per cache tag
 371
 372                 shared_cpu_list:
 373                                 the list of logical cpus sharing the cache
 374
 375                 shared_cpu_map:
 376                                 logical cpu mask containing the list of cpus sharing
 377                                 the cache
 378
 379                 size:
 380                         the total cache size in kB
 381
 382                 type:
 383                         - Instruction: cache that only holds instructions
 384                         - Data: cache that only caches data
 385                         - Unified: cache that holds both data and instructions
 386
 387                 ways_of_associativity:
 388                         degree of freedom in placing a particular block
 389                         of memory in the cache
 390
 391                 write_policy:
 392                         - WriteThrough:
 393                                         data is written to both the cache line
 394                                         and to the block in the lower-level memory
 395                         - WriteBack:
 396                                      data is written only to the cache line and
 397                                      the modified cache line is written to main
 398                                      memory only when it is replaced
 399
 400
 401 What:           /sys/devices/system/cpu/cpu*/cache/index*/id
 402 Date:           September 2016
 403 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
 404 Description:    Cache id
 405
 406                 The id provides a unique number for a specific instance of
 407                 a cache of a particular type. E.g. there may be a level
 408                 3 unified cache on each socket in a server and we may
 409                 assign them ids 0, 1, 2, ...
 410
 411                 Note that id value can be non-contiguous. E.g. level 1
 412                 caches typically exist per core, but there may not be a
 413                 power of two cores on a socket, so these caches may be
 414                 numbered 0, 1, 2, 3, 4, 5, 8, 9, 10, ...
 415
 416 What:           /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats
 417                 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/turbo_stat
 418                 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/sub_turbo_stat
 419                 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/unthrottle
 420                 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/powercap
 421                 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overtemp
 422                 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/supply_fault
 423                 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overcurrent
 424                 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/occ_reset
 425 Date:           March 2016
 426 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
 427                 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
 428 Description:    POWERNV CPUFreq driver's frequency throttle stats directory and
 429                 attributes
 430
 431                 'cpuX/cpufreq/throttle_stats' directory contains the CPU frequency
 432                 throttle stat attributes for the chip. The throttle stats of a cpu
 433                 is common across all the cpus belonging to a chip. Below are the
 434                 throttle attributes exported in the 'throttle_stats' directory:
 435
 436                 - turbo_stat : This file gives the total number of times the max
 437                   frequency is throttled to lower frequency in turbo (at and above
 438                   nominal frequency) range of frequencies.
 439
 440                 - sub_turbo_stat : This file gives the total number of times the
 441                   max frequency is throttled to lower frequency in sub-turbo(below
 442                   nominal frequency) range of frequencies.
 443
 444                 - unthrottle : This file gives the total number of times the max
 445                   frequency is unthrottled after being throttled.
 446
 447                 - powercap : This file gives the total number of times the max
 448                   frequency is throttled due to 'Power Capping'.
 449
 450                 - overtemp : This file gives the total number of times the max
 451                   frequency is throttled due to 'CPU Over Temperature'.
 452
 453                 - supply_fault : This file gives the total number of times the
 454                   max frequency is throttled due to 'Power Supply Failure'.
 455
 456                 - overcurrent : This file gives the total number of times the
 457                   max frequency is throttled due to 'Overcurrent'.
 458
 459                 - occ_reset : This file gives the total number of times the max
 460                   frequency is throttled due to 'OCC Reset'.
 461
 462                 The sysfs attributes representing different throttle reasons like
 463                 powercap, overtemp, supply_fault, overcurrent and occ_reset map to
 464                 the reasons provided by OCC firmware for throttling the frequency.
 465
 466 What:           /sys/devices/system/cpu/cpufreq/policyX/throttle_stats
 467                 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/turbo_stat
 468                 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/sub_turbo_stat
 469                 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/unthrottle
 470                 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/powercap
 471                 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overtemp
 472                 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/supply_fault
 473                 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overcurrent
 474                 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/occ_reset
 475 Date:           March 2016
 476 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
 477                 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
 478 Description:    POWERNV CPUFreq driver's frequency throttle stats directory and
 479                 attributes
 480
 481                 'policyX/throttle_stats' directory and all the attributes are same as
 482                 the /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats directory and
 483                 attributes which give the frequency throttle information of the chip.
 484
 485 What:           /sys/devices/system/cpu/cpuX/regs/
 486                 /sys/devices/system/cpu/cpuX/regs/identification/
 487                 /sys/devices/system/cpu/cpuX/regs/identification/midr_el1
 488                 /sys/devices/system/cpu/cpuX/regs/identification/revidr_el1
 489 Date:           June 2016
 490 Contact:        Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
 491 Description:    AArch64 CPU registers
 492
 493                 'identification' directory exposes the CPU ID registers for
 494                 identifying model and revision of the CPU.
 495
 496 What:           /sys/devices/system/cpu/cpu#/cpu_capacity
 497 Date:           December 2016
 498 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
 499 Description:    information about CPUs heterogeneity.
 500
 501                 cpu_capacity: capacity of cpu#.
 502
 503 What:           /sys/devices/system/cpu/vulnerabilities
 504                 /sys/devices/system/cpu/vulnerabilities/meltdown
 505                 /sys/devices/system/cpu/vulnerabilities/spectre_v1
 506                 /sys/devices/system/cpu/vulnerabilities/spectre_v2
 507                 /sys/devices/system/cpu/vulnerabilities/spec_store_bypass
 508                 /sys/devices/system/cpu/vulnerabilities/l1tf
 509                 /sys/devices/system/cpu/vulnerabilities/mds
 510                 /sys/devices/system/cpu/vulnerabilities/srbds
 511                 /sys/devices/system/cpu/vulnerabilities/tsx_async_abort
 512                 /sys/devices/system/cpu/vulnerabilities/itlb_multihit
 513 Date:           January 2018
 514 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
 515 Description:    Information about CPU vulnerabilities
 516
 517                 The files are named after the code names of CPU
 518                 vulnerabilities. The output of those files reflects the
 519                 state of the CPUs in the system. Possible output values:
 520
 521                 ================  ==============================================
 522                 "Not affected"    CPU is not affected by the vulnerability
 523                 "Vulnerable"      CPU is affected and no mitigation in effect
 524                 "Mitigation: $M"  CPU is affected and mitigation $M is in effect
 525                 ================  ==============================================
 526
 527                 See also: Documentation/admin-guide/hw-vuln/index.rst
 528
 529 What:           /sys/devices/system/cpu/smt
 530                 /sys/devices/system/cpu/smt/active
 531                 /sys/devices/system/cpu/smt/control
 532 Date:           June 2018
 533 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
 534 Description:    Control Symetric Multi Threading (SMT)
 535
 536                 active:  Tells whether SMT is active (enabled and siblings online)
 537
 538                 control: Read/write interface to control SMT. Possible
 539                          values:
 540
 541                          ================ =========================================
 542                          "on"             SMT is enabled
 543                          "off"            SMT is disabled
 544                          "forceoff"       SMT is force disabled. Cannot be changed.
 545                          "notsupported"   SMT is not supported by the CPU
 546                          "notimplemented" SMT runtime toggling is not
 547                                           implemented for the architecture
 548                          ================ =========================================
 549
 550                          If control status is "forceoff" or "notsupported" writes
 551                          are rejected.
 552
 553 What:           /sys/devices/system/cpu/cpu#/power/energy_perf_bias
 554 Date:           March 2019
 555 Contact:        linux-pm@vger.kernel.org
 556 Description:    Intel Energy and Performance Bias Hint (EPB)
 557
 558                 EPB for the given CPU in a sliding scale 0 - 15, where a value
 559                 of 0 corresponds to a hint preference for highest performance
 560                 and a value of 15 corresponds to the maximum energy savings.
 561
 562                 In order to change the EPB value for the CPU, write either
 563                 a number in the 0 - 15 sliding scale above, or one of the
 564                 strings: "performance", "balance-performance", "normal",
 565                 "balance-power", "power" (that represent values reflected by
 566                 their meaning), to this attribute.
 567
 568                 This attribute is present for all online CPUs supporting the
 569                 Intel EPB feature.
 570
 571 What:           /sys/devices/system/cpu/umwait_control
 572                 /sys/devices/system/cpu/umwait_control/enable_c02
 573                 /sys/devices/system/cpu/umwait_control/max_time
 574 Date:           May 2019
 575 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
 576 Description:    Umwait control
 577
 578                 enable_c02: Read/write interface to control umwait C0.2 state
 579                         Read returns C0.2 state status:
 580                                 0: C0.2 is disabled
 581                                 1: C0.2 is enabled
 582
 583                         Write 'y' or '1'  or 'on' to enable C0.2 state.
 584                         Write 'n' or '0'  or 'off' to disable C0.2 state.
 585
 586                         The interface is case insensitive.
 587
 588                 max_time: Read/write interface to control umwait maximum time
 589                           in TSC-quanta that the CPU can reside in either C0.1
 590                           or C0.2 state. The time is an unsigned 32-bit number.
 591                           Note that a value of zero means there is no limit.
 592                           Low order two bits must be zero.
 593
 594 What:           /sys/devices/system/cpu/svm
 595 Date:           August 2019
 596 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
 597                 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
 598 Description:    Secure Virtual Machine
 599
 600                 If 1, it means the system is using the Protected Execution
 601                 Facility in POWER9 and newer processors. i.e., it is a Secure
 602                 Virtual Machine.
 603
 604 What:           /sys/devices/system/cpu/cpuX/purr
 605 Date:           Apr 2005
 606 Contact:        Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
 607 Description:    PURR ticks for this CPU since the system boot.
 608
 609                 The Processor Utilization Resources Register (PURR) is
 610                 a 64-bit counter which provides an estimate of the
 611                 resources used by the CPU thread. The contents of this
 612                 register increases monotonically. This sysfs interface
 613                 exposes the number of PURR ticks for cpuX.
 614
 615 What:           /sys/devices/system/cpu/cpuX/spurr
 616 Date:           Dec 2006
 617 Contact:        Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
 618 Description:    SPURR ticks for this CPU since the system boot.
 619
 620                 The Scaled Processor Utilization Resources Register
 621                 (SPURR) is a 64-bit counter that provides a frequency
 622                 invariant estimate of the resources used by the CPU
 623                 thread. The contents of this register increases
 624                 monotonically. This sysfs interface exposes the number
 625                 of SPURR ticks for cpuX.
 626
 627 What:           /sys/devices/system/cpu/cpuX/idle_purr
 628 Date:           Apr 2020
 629 Contact:        Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
 630 Description:    PURR ticks for cpuX when it was idle.
 631
 632                 This sysfs interface exposes the number of PURR ticks
 633                 for cpuX when it was idle.
 634
 635 What:           /sys/devices/system/cpu/cpuX/idle_spurr
 636 Date:           Apr 2020
 637 Contact:        Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
 638 Description:    SPURR ticks for cpuX when it was idle.
 639
 640                 This sysfs interface exposes the number of SPURR ticks
 641                 for cpuX when it was idle.