1 What: /sys/devices/system/cpu/ 1 What: /sys/devices/system/cpu/
2 Date: pre-git history 2 Date: pre-git history
3 Contact: Linux kernel mailing list <linu 3 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
4 Description: 4 Description:
5 A collection of both global an 5 A collection of both global and individual CPU attributes
6 6
7 Individual CPU attributes are 7 Individual CPU attributes are contained in subdirectories
8 named by the kernel's logical 8 named by the kernel's logical CPU number, e.g.:
9 9
10 /sys/devices/system/cpu/cpuX/ 10 /sys/devices/system/cpu/cpuX/
11 11
12 What: /sys/devices/system/cpu/kernel 12 What: /sys/devices/system/cpu/kernel_max
13 /sys/devices/system/cpu/offlin 13 /sys/devices/system/cpu/offline
14 /sys/devices/system/cpu/online 14 /sys/devices/system/cpu/online
15 /sys/devices/system/cpu/possib 15 /sys/devices/system/cpu/possible
16 /sys/devices/system/cpu/presen 16 /sys/devices/system/cpu/present
17 Date: December 2008 17 Date: December 2008
18 Contact: Linux kernel mailing list <linu 18 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
19 Description: CPU topology files that descri 19 Description: CPU topology files that describe kernel limits related to
20 hotplug. Briefly: 20 hotplug. Briefly:
21 21
22 kernel_max: the maximum cpu in 22 kernel_max: the maximum cpu index allowed by the kernel
23 configuration. 23 configuration.
24 24
25 offline: cpus that are not onl 25 offline: cpus that are not online because they have been
26 HOTPLUGGED off or exceed the l 26 HOTPLUGGED off or exceed the limit of cpus allowed by the
27 kernel configuration (kernel_m 27 kernel configuration (kernel_max above).
28 28
29 online: cpus that are online a 29 online: cpus that are online and being scheduled.
30 30
31 possible: cpus that have been 31 possible: cpus that have been allocated resources and can be
32 brought online if they are pre 32 brought online if they are present.
33 33
34 present: cpus that have been i 34 present: cpus that have been identified as being present in
35 the system. 35 the system.
36 36
37 See Documentation/admin-guide/ 37 See Documentation/admin-guide/cputopology.rst for more information.
38 38
39 39
40 What: /sys/devices/system/cpu/probe 40 What: /sys/devices/system/cpu/probe
41 /sys/devices/system/cpu/releas 41 /sys/devices/system/cpu/release
42 Date: November 2009 42 Date: November 2009
43 Contact: Linux kernel mailing list <linu 43 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
44 Description: Dynamic addition and removal o 44 Description: Dynamic addition and removal of CPU's. This is not hotplug
45 removal, this is meant complet 45 removal, this is meant complete removal/addition of the CPU
46 from the system. 46 from the system.
47 47
48 probe: writes to this file wil 48 probe: writes to this file will dynamically add a CPU to the
49 system. Information written t 49 system. Information written to the file to add CPU's is
50 architecture specific. 50 architecture specific.
51 51
52 release: writes to this file d 52 release: writes to this file dynamically remove a CPU from
53 the system. Information writt 53 the system. Information written to the file to remove CPU's
54 is architecture specific. 54 is architecture specific.
55 55
56 What: /sys/devices/system/cpu/cpuX/n 56 What: /sys/devices/system/cpu/cpuX/node
57 Date: October 2009 57 Date: October 2009
58 Contact: Linux memory management mailin< 58 Contact: Linux memory management mailing list <linux-mm@kvack.org>
59 Description: Discover NUMA node a CPU belon 59 Description: Discover NUMA node a CPU belongs to
60 60
61 When CONFIG_NUMA is enabled, a 61 When CONFIG_NUMA is enabled, a symbolic link that points
62 to the corresponding NUMA node 62 to the corresponding NUMA node directory.
63 63
64 For example, the following sym 64 For example, the following symlink is created for cpu42
65 in NUMA node 2: 65 in NUMA node 2:
66 66
67 /sys/devices/system/cpu/cpu42/ 67 /sys/devices/system/cpu/cpu42/node2 -> ../../node/node2
68 68
69 69
70 What: /sys/devices/system/cpu/cpuX/t 70 What: /sys/devices/system/cpu/cpuX/topology/core_siblings
71 /sys/devices/system/cpu/cpuX/t 71 /sys/devices/system/cpu/cpuX/topology/core_siblings_list
72 /sys/devices/system/cpu/cpuX/t 72 /sys/devices/system/cpu/cpuX/topology/physical_package_id
73 /sys/devices/system/cpu/cpuX/t 73 /sys/devices/system/cpu/cpuX/topology/thread_siblings
74 /sys/devices/system/cpu/cpuX/t 74 /sys/devices/system/cpu/cpuX/topology/thread_siblings_list
75 /sys/devices/system/cpu/cpuX/t 75 /sys/devices/system/cpu/cpuX/topology/ppin
76 Date: December 2008 76 Date: December 2008
77 Contact: Linux kernel mailing list <linu 77 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
78 Description: CPU topology files that descri 78 Description: CPU topology files that describe a logical CPU's relationship
79 to other cores and threads in 79 to other cores and threads in the same physical package.
80 80
81 One cpuX directory is created 81 One cpuX directory is created per logical CPU in the system,
82 e.g. /sys/devices/system/cpu/c 82 e.g. /sys/devices/system/cpu/cpu42/.
83 83
84 Briefly, the files above are: 84 Briefly, the files above are:
85 85
86 core_siblings: internal kernel 86 core_siblings: internal kernel map of cpuX's hardware threads
87 within the same physical_packa 87 within the same physical_package_id.
88 88
89 core_siblings_list: human-read 89 core_siblings_list: human-readable list of the logical CPU
90 numbers within the same physic 90 numbers within the same physical_package_id as cpuX.
91 91
92 physical_package_id: physical 92 physical_package_id: physical package id of cpuX. Typically
93 corresponds to a physical sock 93 corresponds to a physical socket number, but the actual value
94 is architecture and platform d 94 is architecture and platform dependent.
95 95
96 thread_siblings: internal kern 96 thread_siblings: internal kernel map of cpuX's hardware
97 threads within the same core a 97 threads within the same core as cpuX
98 98
99 thread_siblings_list: human-re 99 thread_siblings_list: human-readable list of cpuX's hardware
100 threads within the same core a 100 threads within the same core as cpuX
101 101
102 ppin: human-readable Protected 102 ppin: human-readable Protected Processor Identification
103 Number of the socket the cpu# 103 Number of the socket the cpu# belongs to. There should be
104 one per physical_package_id. F 104 one per physical_package_id. File is readable only to
105 admin. 105 admin.
106 106
107 See Documentation/admin-guide/ 107 See Documentation/admin-guide/cputopology.rst for more information.
108 108
109 109
110 What: /sys/devices/system/cpu/cpuidl 110 What: /sys/devices/system/cpu/cpuidle/available_governors
111 /sys/devices/system/cpu/cpuidl 111 /sys/devices/system/cpu/cpuidle/current_driver
112 /sys/devices/system/cpu/cpuidl 112 /sys/devices/system/cpu/cpuidle/current_governor
113 /sys/devices/system/cpu/cpuidl 113 /sys/devices/system/cpu/cpuidle/current_governer_ro
114 Date: September 2007 114 Date: September 2007
115 Contact: Linux kernel mailing list <linu 115 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
116 Description: Discover cpuidle policy and me 116 Description: Discover cpuidle policy and mechanism
117 117
118 Various CPUs today support mul 118 Various CPUs today support multiple idle levels that are
119 differentiated by varying exit 119 differentiated by varying exit latencies and power
120 consumption during idle. 120 consumption during idle.
121 121
122 Idle policy (governor) is diff 122 Idle policy (governor) is differentiated from idle mechanism
123 (driver). 123 (driver).
124 124
125 available_governors: (RO) disp 125 available_governors: (RO) displays a space separated list of
126 available governors. 126 available governors.
127 127
128 current_driver: (RO) displays 128 current_driver: (RO) displays current idle mechanism.
129 129
130 current_governor: (RW) display 130 current_governor: (RW) displays current idle policy. Users can
131 switch the governor at runtime 131 switch the governor at runtime by writing to this file.
132 132
133 current_governor_ro: (RO) disp 133 current_governor_ro: (RO) displays current idle policy.
134 134
135 See Documentation/admin-guide/ 135 See Documentation/admin-guide/pm/cpuidle.rst and
136 Documentation/driver-api/pm/cp 136 Documentation/driver-api/pm/cpuidle.rst for more information.
137 137
138 138
139 What: /sys/devices/system/cpu/cpuX/c 139 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/name
140 /sys/devices/system/cpu/cpuX/c 140 /sys/devices/system/cpu/cpuX/cpuidle/stateN/latency
141 /sys/devices/system/cpu/cpuX/c 141 /sys/devices/system/cpu/cpuX/cpuidle/stateN/power
142 /sys/devices/system/cpu/cpuX/c 142 /sys/devices/system/cpu/cpuX/cpuidle/stateN/time
143 /sys/devices/system/cpu/cpuX/c 143 /sys/devices/system/cpu/cpuX/cpuidle/stateN/usage
144 /sys/devices/system/cpu/cpuX/c 144 /sys/devices/system/cpu/cpuX/cpuidle/stateN/above
145 /sys/devices/system/cpu/cpuX/c 145 /sys/devices/system/cpu/cpuX/cpuidle/stateN/below
146 Date: September 2007 146 Date: September 2007
147 KernelVersion: v2.6.24 147 KernelVersion: v2.6.24
148 Contact: Linux power management list <li 148 Contact: Linux power management list <linux-pm@vger.kernel.org>
149 Description: 149 Description:
150 The directory /sys/devices/sys 150 The directory /sys/devices/system/cpu/cpuX/cpuidle contains per
151 logical CPU specific cpuidle i 151 logical CPU specific cpuidle information for each online cpu X.
152 The processor idle states whic 152 The processor idle states which are available for use have the
153 following attributes: 153 following attributes:
154 154
155 ======== ==== ================ 155 ======== ==== =================================================
156 name: (RO) Name of the idle 156 name: (RO) Name of the idle state (string).
157 157
158 latency: (RO) The latency to e 158 latency: (RO) The latency to exit out of this idle state (in
159 microseconds). 159 microseconds).
160 160
161 power: (RO) The power consum 161 power: (RO) The power consumed while in this idle state (in
162 milliwatts). 162 milliwatts).
163 163
164 time: (RO) The total time s 164 time: (RO) The total time spent in this idle state
165 (in microseconds 165 (in microseconds).
166 166
167 usage: (RO) Number of times 167 usage: (RO) Number of times this state was entered (a count).
168 168
169 above: (RO) Number of times 169 above: (RO) Number of times this state was entered, but the
170 observed CPU idl 170 observed CPU idle duration was too short for it
171 (a count). 171 (a count).
172 172
173 below: (RO) Number of times 173 below: (RO) Number of times this state was entered, but the
174 observed CPU idl 174 observed CPU idle duration was too long for it
175 (a count). 175 (a count).
176 ======== ==== ================ 176 ======== ==== =================================================
177 177
178 What: /sys/devices/system/cpu/cpuX/c 178 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/desc
179 Date: February 2008 179 Date: February 2008
180 KernelVersion: v2.6.25 180 KernelVersion: v2.6.25
181 Contact: Linux power management list <li 181 Contact: Linux power management list <linux-pm@vger.kernel.org>
182 Description: 182 Description:
183 (RO) A small description about 183 (RO) A small description about the idle state (string).
184 184
185 185
186 What: /sys/devices/system/cpu/cpuX/c 186 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/disable
187 Date: March 2012 187 Date: March 2012
188 KernelVersion: v3.10 188 KernelVersion: v3.10
189 Contact: Linux power management list <li 189 Contact: Linux power management list <linux-pm@vger.kernel.org>
190 Description: 190 Description:
191 (RW) Option to disable this id 191 (RW) Option to disable this idle state (bool). The behavior and
192 the effect of the disable vari 192 the effect of the disable variable depends on the implementation
193 of a particular governor. In t 193 of a particular governor. In the ladder governor, for example,
194 it is not coherent, i.e. if on 194 it is not coherent, i.e. if one is disabling a light state, then
195 all deeper states are disabled 195 all deeper states are disabled as well, but the disable variable
196 does not reflect it. Likewise, 196 does not reflect it. Likewise, if one enables a deep state but a
197 lighter state still is disable 197 lighter state still is disabled, then this has no effect.
198 198
199 What: /sys/devices/system/cpu/cpuX/c 199 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/default_status
200 Date: December 2019 200 Date: December 2019
201 KernelVersion: v5.6 201 KernelVersion: v5.6
202 Contact: Linux power management list <li 202 Contact: Linux power management list <linux-pm@vger.kernel.org>
203 Description: 203 Description:
204 (RO) The default status of thi 204 (RO) The default status of this state, "enabled" or "disabled".
205 205
206 What: /sys/devices/system/cpu/cpuX/c 206 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/residency
207 Date: March 2014 207 Date: March 2014
208 KernelVersion: v3.15 208 KernelVersion: v3.15
209 Contact: Linux power management list <li 209 Contact: Linux power management list <linux-pm@vger.kernel.org>
210 Description: 210 Description:
211 (RO) Display the target reside 211 (RO) Display the target residency i.e. the minimum amount of
212 time (in microseconds) this cp 212 time (in microseconds) this cpu should spend in this idle state
213 to make the transition worth t 213 to make the transition worth the effort.
214 214
215 What: /sys/devices/system/cpu/cpuX/c 215 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/
216 Date: March 2018 216 Date: March 2018
217 KernelVersion: v4.17 217 KernelVersion: v4.17
218 Contact: Linux power management list <li 218 Contact: Linux power management list <linux-pm@vger.kernel.org>
219 Description: 219 Description:
220 Idle state usage statistics re 220 Idle state usage statistics related to suspend-to-idle.
221 221
222 This attribute group is only p 222 This attribute group is only present for states that can be
223 used in suspend-to-idle with s 223 used in suspend-to-idle with suspended timekeeping.
224 224
225 What: /sys/devices/system/cpu/cpuX/c 225 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/time
226 Date: March 2018 226 Date: March 2018
227 KernelVersion: v4.17 227 KernelVersion: v4.17
228 Contact: Linux power management list <li 228 Contact: Linux power management list <linux-pm@vger.kernel.org>
229 Description: 229 Description:
230 Total time spent by the CPU in 230 Total time spent by the CPU in suspend-to-idle (with scheduler
231 tick suspended) after requesti 231 tick suspended) after requesting this state.
232 232
233 What: /sys/devices/system/cpu/cpuX/c 233 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/usage
234 Date: March 2018 234 Date: March 2018
235 KernelVersion: v4.17 235 KernelVersion: v4.17
236 Contact: Linux power management list <li 236 Contact: Linux power management list <linux-pm@vger.kernel.org>
237 Description: 237 Description:
238 Total number of times this sta 238 Total number of times this state has been requested by the CPU
239 while entering suspend-to-idle 239 while entering suspend-to-idle.
240 240
241 What: /sys/devices/system/cpu/cpuX/c 241 What: /sys/devices/system/cpu/cpuX/cpufreq/*
242 Date: pre-git history 242 Date: pre-git history
243 Contact: linux-pm@vger.kernel.org 243 Contact: linux-pm@vger.kernel.org
244 Description: Discover and change clock spee 244 Description: Discover and change clock speed of CPUs
245 245
246 Clock scaling allows you to ch 246 Clock scaling allows you to change the clock speed of the
247 CPUs on the fly. This is a nic 247 CPUs on the fly. This is a nice method to save battery
248 power, because the lower the c 248 power, because the lower the clock speed, the less power
249 the CPU consumes. 249 the CPU consumes.
250 250
251 There are many knobs to tweak 251 There are many knobs to tweak in this directory.
252 252
253 See files in Documentation/cpu 253 See files in Documentation/cpu-freq/ for more information.
254 254
255 255
256 What: /sys/devices/system/cpu/cpuX/c 256 What: /sys/devices/system/cpu/cpuX/cpufreq/freqdomain_cpus
257 Date: June 2013 257 Date: June 2013
258 Contact: linux-pm@vger.kernel.org 258 Contact: linux-pm@vger.kernel.org
259 Description: Discover CPUs in the same CPU 259 Description: Discover CPUs in the same CPU frequency coordination domain
260 260
261 freqdomain_cpus is the list of 261 freqdomain_cpus is the list of CPUs (online+offline) that share
262 the same clock/freq domain (po 262 the same clock/freq domain (possibly at the hardware level).
263 That information may be hidden 263 That information may be hidden from the cpufreq core and the
264 value of related_cpus may be d 264 value of related_cpus may be different from freqdomain_cpus. This
265 attribute is useful for user s 265 attribute is useful for user space DVFS controllers to get better
266 power/performance results for 266 power/performance results for platforms using acpi-cpufreq.
267 267
268 This file is only present if t 268 This file is only present if the acpi-cpufreq or the cppc-cpufreq
269 drivers are in use. 269 drivers are in use.
270 270
271 271
272 What: /sys/devices/system/cpu/cpu*/c 272 What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
273 Date: August 2008 273 Date: August 2008
274 KernelVersion: 2.6.27 274 KernelVersion: 2.6.27
275 Contact: Linux kernel mailing list <linu 275 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
276 Description: Disable L3 cache indices 276 Description: Disable L3 cache indices
277 277
278 These files exist in every CPU 278 These files exist in every CPU's cache/index3 directory. Each
279 cache_disable_{0,1} file corre 279 cache_disable_{0,1} file corresponds to one disable slot which
280 can be used to disable a cache 280 can be used to disable a cache index. Reading from these files
281 on a processor with this funct 281 on a processor with this functionality will return the currently
282 disabled index for that node. 282 disabled index for that node. There is one L3 structure per
283 node, or per internal node on 283 node, or per internal node on MCM machines. Writing a valid
284 index to one of these files wi 284 index to one of these files will cause the specified cache
285 index to be disabled. 285 index to be disabled.
286 286
287 All AMD processors with L3 cac 287 All AMD processors with L3 caches provide this functionality.
288 For details, see BKDGs at 288 For details, see BKDGs at
289 https://www.amd.com/en/support 289 https://www.amd.com/en/support/tech-docs?keyword=bios+kernel
290 290
291 291
292 What: /sys/devices/system/cpu/cpufre 292 What: /sys/devices/system/cpu/cpufreq/boost
293 Date: August 2012 293 Date: August 2012
294 Contact: Linux kernel mailing list <linu 294 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
295 Description: Processor frequency boosting c 295 Description: Processor frequency boosting control
296 296
297 This switch controls the boost 297 This switch controls the boost setting for the whole system.
298 Boosting allows the CPU and th 298 Boosting allows the CPU and the firmware to run at a frequency
299 beyond its nominal limit. 299 beyond its nominal limit.
300 300
301 More details can be found in 301 More details can be found in
302 Documentation/admin-guide/pm/c 302 Documentation/admin-guide/pm/cpufreq.rst
303 303
304 304
305 What: /sys/devices/system/cpu/cpuX/c 305 What: /sys/devices/system/cpu/cpuX/crash_notes
306 /sys/devices/system/cpu/cpuX/c 306 /sys/devices/system/cpu/cpuX/crash_notes_size
307 Date: April 2013 307 Date: April 2013
308 Contact: kexec@lists.infradead.org 308 Contact: kexec@lists.infradead.org
309 Description: address and size of the percpu 309 Description: address and size of the percpu note.
310 310
311 crash_notes: the physical addr 311 crash_notes: the physical address of the memory that holds the
312 note of cpuX. 312 note of cpuX.
313 313
314 crash_notes_size: size of the 314 crash_notes_size: size of the note of cpuX.
315 315
316 316
317 What: /sys/devices/system/cpu/intel_ 317 What: /sys/devices/system/cpu/intel_pstate/max_perf_pct
318 /sys/devices/system/cpu/intel_ 318 /sys/devices/system/cpu/intel_pstate/min_perf_pct
319 /sys/devices/system/cpu/intel_ 319 /sys/devices/system/cpu/intel_pstate/no_turbo
320 Date: February 2013 320 Date: February 2013
321 Contact: linux-pm@vger.kernel.org 321 Contact: linux-pm@vger.kernel.org
322 Description: Parameters for the Intel P-sta 322 Description: Parameters for the Intel P-state driver
323 323
324 Logic for selecting the curren 324 Logic for selecting the current P-state in Intel
325 Sandybridge+ processors. The t 325 Sandybridge+ processors. The three knobs control
326 limits for the P-state that wi 326 limits for the P-state that will be requested by the
327 driver. 327 driver.
328 328
329 max_perf_pct: limits the maxim 329 max_perf_pct: limits the maximum P state that will be requested by
330 the driver stated as a percent 330 the driver stated as a percentage of the available performance.
331 331
332 min_perf_pct: limits the minim 332 min_perf_pct: limits the minimum P state that will be requested by
333 the driver stated as a percent 333 the driver stated as a percentage of the available performance.
334 334
335 no_turbo: limits the driver to 335 no_turbo: limits the driver to selecting P states below the turbo
336 frequency range. 336 frequency range.
337 337
338 More details can be found in 338 More details can be found in
339 Documentation/admin-guide/pm/i 339 Documentation/admin-guide/pm/intel_pstate.rst
340 340
341 What: /sys/devices/system/cpu/cpu*/c 341 What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below>
342 Date: July 2014(documented, existed 342 Date: July 2014(documented, existed before August 2008)
343 Contact: Sudeep Holla <sudeep.holla@arm. 343 Contact: Sudeep Holla <sudeep.holla@arm.com>
344 Linux kernel mailing list <linu 344 Linux kernel mailing list <linux-kernel@vger.kernel.org>
345 Description: Parameters for the CPU cache a 345 Description: Parameters for the CPU cache attributes
346 346
347 allocation_policy: 347 allocation_policy:
348 - WriteAllocate: 348 - WriteAllocate:
349 alloca 349 allocate a memory location to a cache line
350 on a c 350 on a cache miss because of a write
351 - ReadAllocate: 351 - ReadAllocate:
352 alloca 352 allocate a memory location to a cache line
353 on a c 353 on a cache miss because of a read
354 - ReadWriteAllocate: 354 - ReadWriteAllocate:
355 both w 355 both writeallocate and readallocate
356 356
>> 357 attributes:
>> 358 LEGACY used only on IA64 and is same as write_policy
>> 359
357 coherency_line_size: 360 coherency_line_size:
358 the minim 361 the minimum amount of data in bytes that gets
359 transferr 362 transferred from memory to cache
360 363
361 level: 364 level:
362 the cache hierarchy in 365 the cache hierarchy in the multi-level cache configuration
363 366
364 number_of_sets: 367 number_of_sets:
365 total number o 368 total number of sets in the cache, a set is a
366 collection of 369 collection of cache lines with the same cache index
367 370
368 physical_line_partition: 371 physical_line_partition:
369 number of phys 372 number of physical cache line per cache tag
370 373
371 shared_cpu_list: 374 shared_cpu_list:
372 the list of lo 375 the list of logical cpus sharing the cache
373 376
374 shared_cpu_map: 377 shared_cpu_map:
375 logical cpu ma 378 logical cpu mask containing the list of cpus sharing
376 the cache 379 the cache
377 380
378 size: 381 size:
379 the total cache size i 382 the total cache size in kB
380 383
381 type: 384 type:
382 - Instruction: cache t 385 - Instruction: cache that only holds instructions
383 - Data: cache that onl 386 - Data: cache that only caches data
384 - Unified: cache that 387 - Unified: cache that holds both data and instructions
385 388
386 ways_of_associativity: 389 ways_of_associativity:
387 degree of freedom in p 390 degree of freedom in placing a particular block
388 of memory in the cache 391 of memory in the cache
389 392
390 write_policy: 393 write_policy:
391 - WriteThrough: 394 - WriteThrough:
392 data i 395 data is written to both the cache line
393 and to 396 and to the block in the lower-level memory
394 - WriteBack: 397 - WriteBack:
395 data is w 398 data is written only to the cache line and
396 the modif 399 the modified cache line is written to main
397 memory on 400 memory only when it is replaced
398 401
399 402
400 What: /sys/devices/system/cpu/cpu*/c 403 What: /sys/devices/system/cpu/cpu*/cache/index*/id
401 Date: September 2016 404 Date: September 2016
402 Contact: Linux kernel mailing list <linu 405 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
403 Description: Cache id 406 Description: Cache id
404 407
405 The id provides a unique numbe 408 The id provides a unique number for a specific instance of
406 a cache of a particular type. 409 a cache of a particular type. E.g. there may be a level
407 3 unified cache on each socket 410 3 unified cache on each socket in a server and we may
408 assign them ids 0, 1, 2, ... 411 assign them ids 0, 1, 2, ...
409 412
410 Note that id value can be non- 413 Note that id value can be non-contiguous. E.g. level 1
411 caches typically exist per cor 414 caches typically exist per core, but there may not be a
412 power of two cores on a socket 415 power of two cores on a socket, so these caches may be
413 numbered 0, 1, 2, 3, 4, 5, 8, 416 numbered 0, 1, 2, 3, 4, 5, 8, 9, 10, ...
414 417
415 What: /sys/devices/system/cpu/cpuX/c 418 What: /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats
416 /sys/devices/system/cpu/cpuX/c 419 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/turbo_stat
417 /sys/devices/system/cpu/cpuX/c 420 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/sub_turbo_stat
418 /sys/devices/system/cpu/cpuX/c 421 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/unthrottle
419 /sys/devices/system/cpu/cpuX/c 422 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/powercap
420 /sys/devices/system/cpu/cpuX/c 423 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overtemp
421 /sys/devices/system/cpu/cpuX/c 424 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/supply_fault
422 /sys/devices/system/cpu/cpuX/c 425 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overcurrent
423 /sys/devices/system/cpu/cpuX/c 426 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/occ_reset
424 Date: March 2016 427 Date: March 2016
425 Contact: Linux kernel mailing list <linu 428 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
426 Linux for PowerPC mailing list< !! 429 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
427 Description: POWERNV CPUFreq driver's frequ 430 Description: POWERNV CPUFreq driver's frequency throttle stats directory and
428 attributes 431 attributes
429 432
430 'cpuX/cpufreq/throttle_stats' 433 'cpuX/cpufreq/throttle_stats' directory contains the CPU frequency
431 throttle stat attributes for t 434 throttle stat attributes for the chip. The throttle stats of a cpu
432 is common across all the cpus 435 is common across all the cpus belonging to a chip. Below are the
433 throttle attributes exported i 436 throttle attributes exported in the 'throttle_stats' directory:
434 437
435 - turbo_stat : This file gives 438 - turbo_stat : This file gives the total number of times the max
436 frequency is throttled to lo 439 frequency is throttled to lower frequency in turbo (at and above
437 nominal frequency) range of 440 nominal frequency) range of frequencies.
438 441
439 - sub_turbo_stat : This file g 442 - sub_turbo_stat : This file gives the total number of times the
440 max frequency is throttled t 443 max frequency is throttled to lower frequency in sub-turbo(below
441 nominal frequency) range of 444 nominal frequency) range of frequencies.
442 445
443 - unthrottle : This file gives 446 - unthrottle : This file gives the total number of times the max
444 frequency is unthrottled aft 447 frequency is unthrottled after being throttled.
445 448
446 - powercap : This file gives t 449 - powercap : This file gives the total number of times the max
447 frequency is throttled due t 450 frequency is throttled due to 'Power Capping'.
448 451
449 - overtemp : This file gives t 452 - overtemp : This file gives the total number of times the max
450 frequency is throttled due t 453 frequency is throttled due to 'CPU Over Temperature'.
451 454
452 - supply_fault : This file giv 455 - supply_fault : This file gives the total number of times the
453 max frequency is throttled d 456 max frequency is throttled due to 'Power Supply Failure'.
454 457
455 - overcurrent : This file give 458 - overcurrent : This file gives the total number of times the
456 max frequency is throttled d 459 max frequency is throttled due to 'Overcurrent'.
457 460
458 - occ_reset : This file gives 461 - occ_reset : This file gives the total number of times the max
459 frequency is throttled due t 462 frequency is throttled due to 'OCC Reset'.
460 463
461 The sysfs attributes represent 464 The sysfs attributes representing different throttle reasons like
462 powercap, overtemp, supply_fau 465 powercap, overtemp, supply_fault, overcurrent and occ_reset map to
463 the reasons provided by OCC fi 466 the reasons provided by OCC firmware for throttling the frequency.
464 467
465 What: /sys/devices/system/cpu/cpufre 468 What: /sys/devices/system/cpu/cpufreq/policyX/throttle_stats
466 /sys/devices/system/cpu/cpufre 469 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/turbo_stat
467 /sys/devices/system/cpu/cpufre 470 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/sub_turbo_stat
468 /sys/devices/system/cpu/cpufre 471 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/unthrottle
469 /sys/devices/system/cpu/cpufre 472 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/powercap
470 /sys/devices/system/cpu/cpufre 473 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overtemp
471 /sys/devices/system/cpu/cpufre 474 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/supply_fault
472 /sys/devices/system/cpu/cpufre 475 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overcurrent
473 /sys/devices/system/cpu/cpufre 476 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/occ_reset
474 Date: March 2016 477 Date: March 2016
475 Contact: Linux kernel mailing list <linu 478 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
476 Linux for PowerPC mailing list< !! 479 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
477 Description: POWERNV CPUFreq driver's frequ 480 Description: POWERNV CPUFreq driver's frequency throttle stats directory and
478 attributes 481 attributes
479 482
480 'policyX/throttle_stats' direc 483 'policyX/throttle_stats' directory and all the attributes are same as
481 the /sys/devices/system/cpu/cp 484 the /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats directory and
482 attributes which give the freq 485 attributes which give the frequency throttle information of the chip.
483 486
484 What: /sys/devices/system/cpu/cpuX/r 487 What: /sys/devices/system/cpu/cpuX/regs/
485 /sys/devices/system/cpu/cpuX/r 488 /sys/devices/system/cpu/cpuX/regs/identification/
486 /sys/devices/system/cpu/cpuX/r 489 /sys/devices/system/cpu/cpuX/regs/identification/midr_el1
487 /sys/devices/system/cpu/cpuX/r 490 /sys/devices/system/cpu/cpuX/regs/identification/revidr_el1
488 /sys/devices/system/cpu/cpuX/r 491 /sys/devices/system/cpu/cpuX/regs/identification/smidr_el1
489 Date: June 2016 492 Date: June 2016
490 Contact: Linux ARM Kernel Mailing list < 493 Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
491 Description: AArch64 CPU registers 494 Description: AArch64 CPU registers
492 495
493 'identification' directory exp 496 'identification' directory exposes the CPU ID registers for
494 identifying model and revision 497 identifying model and revision of the CPU and SMCU.
495 498
496 What: /sys/devices/system/cpu/aarch3 499 What: /sys/devices/system/cpu/aarch32_el0
497 Date: May 2021 500 Date: May 2021
498 Contact: Linux ARM Kernel Mailing list < 501 Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
499 Description: Identifies the subset of CPUs 502 Description: Identifies the subset of CPUs in the system that can execute
500 AArch32 (32-bit ARM) applicati 503 AArch32 (32-bit ARM) applications. If present, the same format as
501 /sys/devices/system/cpu/{offli 504 /sys/devices/system/cpu/{offline,online,possible,present} is used.
502 If absent, then all or none of 505 If absent, then all or none of the CPUs can execute AArch32
503 applications and execve() will 506 applications and execve() will behave accordingly.
504 507
505 What: /sys/devices/system/cpu/cpuX/c 508 What: /sys/devices/system/cpu/cpuX/cpu_capacity
506 Date: December 2016 509 Date: December 2016
507 Contact: Linux kernel mailing list <linu 510 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
508 Description: information about CPUs heterog 511 Description: information about CPUs heterogeneity.
509 512
510 cpu_capacity: capacity of cpuX 513 cpu_capacity: capacity of cpuX.
511 514
512 What: /sys/devices/system/cpu/vulner 515 What: /sys/devices/system/cpu/vulnerabilities
513 /sys/devices/system/cpu/vulner <<
514 /sys/devices/system/cpu/vulner <<
515 /sys/devices/system/cpu/vulner <<
516 /sys/devices/system/cpu/vulner <<
517 /sys/devices/system/cpu/vulner 516 /sys/devices/system/cpu/vulnerabilities/meltdown
518 /sys/devices/system/cpu/vulner <<
519 /sys/devices/system/cpu/vulner <<
520 /sys/devices/system/cpu/vulner <<
521 /sys/devices/system/cpu/vulner <<
522 /sys/devices/system/cpu/vulner 517 /sys/devices/system/cpu/vulnerabilities/spectre_v1
523 /sys/devices/system/cpu/vulner 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
524 /sys/devices/system/cpu/vulner 522 /sys/devices/system/cpu/vulnerabilities/srbds
525 /sys/devices/system/cpu/vulner 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
526 Date: January 2018 527 Date: January 2018
527 Contact: Linux kernel mailing list <linu 528 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
528 Description: Information about CPU vulnerab 529 Description: Information about CPU vulnerabilities
529 530
530 The files are named after the 531 The files are named after the code names of CPU
531 vulnerabilities. The output of 532 vulnerabilities. The output of those files reflects the
532 state of the CPUs in the syste 533 state of the CPUs in the system. Possible output values:
533 534
534 ================ ============ 535 ================ ==============================================
535 "Not affected" CPU is not a 536 "Not affected" CPU is not affected by the vulnerability
536 "Vulnerable" CPU is affec 537 "Vulnerable" CPU is affected and no mitigation in effect
537 "Mitigation: $M" CPU is affec 538 "Mitigation: $M" CPU is affected and mitigation $M is in effect
538 ================ ============ 539 ================ ==============================================
539 540
540 See also: Documentation/admin- 541 See also: Documentation/admin-guide/hw-vuln/index.rst
541 542
542 What: /sys/devices/system/cpu/smt 543 What: /sys/devices/system/cpu/smt
543 /sys/devices/system/cpu/smt/ac 544 /sys/devices/system/cpu/smt/active
544 /sys/devices/system/cpu/smt/co 545 /sys/devices/system/cpu/smt/control
545 Date: June 2018 546 Date: June 2018
546 Contact: Linux kernel mailing list <linu 547 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
547 Description: Control Symmetric Multi Thread 548 Description: Control Symmetric Multi Threading (SMT)
548 549
549 active: Tells whether SMT is 550 active: Tells whether SMT is active (enabled and siblings online)
550 551
551 control: Read/write interface 552 control: Read/write interface to control SMT. Possible
552 values: 553 values:
553 554
554 ================ ==== 555 ================ =========================================
555 "on" SMT 556 "on" SMT is enabled
556 "off" SMT 557 "off" SMT is disabled
557 "<N>" SMT <<
558 "forceoff" SMT 558 "forceoff" SMT is force disabled. Cannot be changed.
559 "notsupported" SMT 559 "notsupported" SMT is not supported by the CPU
560 "notimplemented" SMT 560 "notimplemented" SMT runtime toggling is not
561 impl 561 implemented for the architecture
562 ================ ==== 562 ================ =========================================
563 563
564 If control status is 564 If control status is "forceoff" or "notsupported" writes
565 are rejected. Note th !! 565 are rejected.
566 offline cores. <<
567 566
568 What: /sys/devices/system/cpu/cpuX/p 567 What: /sys/devices/system/cpu/cpuX/power/energy_perf_bias
569 Date: March 2019 568 Date: March 2019
570 Contact: linux-pm@vger.kernel.org 569 Contact: linux-pm@vger.kernel.org
571 Description: Intel Energy and Performance B 570 Description: Intel Energy and Performance Bias Hint (EPB)
572 571
573 EPB for the given CPU in a sli 572 EPB for the given CPU in a sliding scale 0 - 15, where a value
574 of 0 corresponds to a hint pre 573 of 0 corresponds to a hint preference for highest performance
575 and a value of 15 corresponds 574 and a value of 15 corresponds to the maximum energy savings.
576 575
577 In order to change the EPB val 576 In order to change the EPB value for the CPU, write either
578 a number in the 0 - 15 sliding 577 a number in the 0 - 15 sliding scale above, or one of the
579 strings: "performance", "balan 578 strings: "performance", "balance-performance", "normal",
580 "balance-power", "power" (that 579 "balance-power", "power" (that represent values reflected by
581 their meaning), to this attrib 580 their meaning), to this attribute.
582 581
583 This attribute is present for 582 This attribute is present for all online CPUs supporting the
584 Intel EPB feature. 583 Intel EPB feature.
585 584
586 What: /sys/devices/system/cpu/umwait 585 What: /sys/devices/system/cpu/umwait_control
587 /sys/devices/system/cpu/umwait 586 /sys/devices/system/cpu/umwait_control/enable_c02
588 /sys/devices/system/cpu/umwait 587 /sys/devices/system/cpu/umwait_control/max_time
589 Date: May 2019 588 Date: May 2019
590 Contact: Linux kernel mailing list <linu 589 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
591 Description: Umwait control 590 Description: Umwait control
592 591
593 enable_c02: Read/write interfa 592 enable_c02: Read/write interface to control umwait C0.2 state
594 Read returns C0.2 stat 593 Read returns C0.2 state status:
595 0: C0.2 is dis 594 0: C0.2 is disabled
596 1: C0.2 is ena 595 1: C0.2 is enabled
597 596
598 Write 'y' or '1' or ' 597 Write 'y' or '1' or 'on' to enable C0.2 state.
599 Write 'n' or '0' or ' 598 Write 'n' or '0' or 'off' to disable C0.2 state.
600 599
601 The interface is case 600 The interface is case insensitive.
602 601
603 max_time: Read/write interface 602 max_time: Read/write interface to control umwait maximum time
604 in TSC-quanta that t 603 in TSC-quanta that the CPU can reside in either C0.1
605 or C0.2 state. The t 604 or C0.2 state. The time is an unsigned 32-bit number.
606 Note that a value of 605 Note that a value of zero means there is no limit.
607 Low order two bits m 606 Low order two bits must be zero.
608 607
609 What: /sys/devices/system/cpu/sev <<
610 /sys/devices/system/cpu/sev/vm <<
611 Date: May 2024 <<
612 Contact: Linux kernel mailing list <linu <<
613 Description: Secure Encrypted Virtualizatio <<
614 <<
615 This directory is only present <<
616 <<
617 vmpl: Reports the Virtual Mach <<
618 the SEV-SNP guest is run <<
619 <<
620 <<
621 What: /sys/devices/system/cpu/svm 608 What: /sys/devices/system/cpu/svm
622 Date: August 2019 609 Date: August 2019
623 Contact: Linux kernel mailing list <linu 610 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
624 Linux for PowerPC mailing list< !! 611 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
625 Description: Secure Virtual Machine 612 Description: Secure Virtual Machine
626 613
627 If 1, it means the system is u 614 If 1, it means the system is using the Protected Execution
628 Facility in POWER9 and newer p 615 Facility in POWER9 and newer processors. i.e., it is a Secure
629 Virtual Machine. 616 Virtual Machine.
630 617
631 What: /sys/devices/system/cpu/cpuX/p 618 What: /sys/devices/system/cpu/cpuX/purr
632 Date: Apr 2005 619 Date: Apr 2005
633 Contact: Linux for PowerPC mailing list< !! 620 Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
634 Description: PURR ticks for this CPU since 621 Description: PURR ticks for this CPU since the system boot.
635 622
636 The Processor Utilization Reso 623 The Processor Utilization Resources Register (PURR) is
637 a 64-bit counter which provide 624 a 64-bit counter which provides an estimate of the
638 resources used by the CPU thre 625 resources used by the CPU thread. The contents of this
639 register increases monotonical 626 register increases monotonically. This sysfs interface
640 exposes the number of PURR tic 627 exposes the number of PURR ticks for cpuX.
641 628
642 What: /sys/devices/system/cpu/cpuX/s 629 What: /sys/devices/system/cpu/cpuX/spurr
643 Date: Dec 2006 630 Date: Dec 2006
644 Contact: Linux for PowerPC mailing list< !! 631 Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
645 Description: SPURR ticks for this CPU since 632 Description: SPURR ticks for this CPU since the system boot.
646 633
647 The Scaled Processor Utilizati 634 The Scaled Processor Utilization Resources Register
648 (SPURR) is a 64-bit counter th 635 (SPURR) is a 64-bit counter that provides a frequency
649 invariant estimate of the reso 636 invariant estimate of the resources used by the CPU
650 thread. The contents of this r 637 thread. The contents of this register increases
651 monotonically. This sysfs inte 638 monotonically. This sysfs interface exposes the number
652 of SPURR ticks for cpuX. 639 of SPURR ticks for cpuX.
653 640
654 What: /sys/devices/system/cpu/cpuX/i 641 What: /sys/devices/system/cpu/cpuX/idle_purr
655 Date: Apr 2020 642 Date: Apr 2020
656 Contact: Linux for PowerPC mailing list< !! 643 Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
657 Description: PURR ticks for cpuX when it wa 644 Description: PURR ticks for cpuX when it was idle.
658 645
659 This sysfs interface exposes t 646 This sysfs interface exposes the number of PURR ticks
660 for cpuX when it was idle. 647 for cpuX when it was idle.
661 648
662 What: /sys/devices/system/cpu/cpuX/i 649 What: /sys/devices/system/cpu/cpuX/idle_spurr
663 Date: Apr 2020 650 Date: Apr 2020
664 Contact: Linux for PowerPC mailing list< !! 651 Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
665 Description: SPURR ticks for cpuX when it w 652 Description: SPURR ticks for cpuX when it was idle.
666 653
667 This sysfs interface exposes t 654 This sysfs interface exposes the number of SPURR ticks
668 for cpuX when it was idle. 655 for cpuX when it was idle.
669 656
670 What: /sys/devices/system/cpu/cpuX/m 657 What: /sys/devices/system/cpu/cpuX/mte_tcf_preferred
671 Date: July 2021 658 Date: July 2021
672 Contact: Linux ARM Kernel Mailing list < 659 Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
673 Description: Preferred MTE tag checking mod 660 Description: Preferred MTE tag checking mode
674 661
675 When a user program specifies 662 When a user program specifies more than one MTE tag checking
676 mode, this sysfs node is used 663 mode, this sysfs node is used to specify which mode should
677 be preferred when scheduling a 664 be preferred when scheduling a task on that CPU. Possible
678 values: 665 values:
679 666
680 ================ ============ 667 ================ ==============================================
681 "sync" Prefer synch 668 "sync" Prefer synchronous mode
682 "asymm" Prefer asymm 669 "asymm" Prefer asymmetric mode
683 "async" Prefer async 670 "async" Prefer asynchronous mode
684 ================ ============ 671 ================ ==============================================
685 672
686 See also: Documentation/arch/a !! 673 See also: Documentation/arm64/memory-tagging-extension.rst
687 674
688 What: /sys/devices/system/cpu/nohz_f 675 What: /sys/devices/system/cpu/nohz_full
689 Date: Apr 2015 676 Date: Apr 2015
690 Contact: Linux kernel mailing list <linu 677 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
691 Description: 678 Description:
692 (RO) the list of CPUs that are 679 (RO) the list of CPUs that are in nohz_full mode.
693 These CPUs are set by boot par 680 These CPUs are set by boot parameter "nohz_full=".
694 681
695 What: /sys/devices/system/cpu/isolat 682 What: /sys/devices/system/cpu/isolated
696 Date: Apr 2015 683 Date: Apr 2015
697 Contact: Linux kernel mailing list <linu 684 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
698 Description: 685 Description:
699 (RO) the list of CPUs that are 686 (RO) the list of CPUs that are isolated and don't
700 participate in load balancing. 687 participate in load balancing. These CPUs are set by
701 boot parameter "isolcpus=". 688 boot parameter "isolcpus=".
702 <<
703 What: /sys/devices/system/cpu/crash_ <<
704 Date: Aug 2023 <<
705 Contact: Linux kernel mailing list <linu <<
706 Description: <<
707 (RO) indicates whether or not <<
708 segments on memory hot un/plug <<
709 need to reload kdump kernel. <<
710 <<
711 What: /sys/devices/system/cpu/enable <<
712 Date: Nov 2022 <<
713 Contact: Linux kernel mailing list <linu <<
714 Description: <<
715 (RO) the list of CPUs that can <<
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