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_id
>> 71 /sys/devices/system/cpu/cpuX/topology/core_siblings
71 /sys/devices/system/cpu/cpuX/t 72 /sys/devices/system/cpu/cpuX/topology/core_siblings_list
72 /sys/devices/system/cpu/cpuX/t 73 /sys/devices/system/cpu/cpuX/topology/physical_package_id
73 /sys/devices/system/cpu/cpuX/t 74 /sys/devices/system/cpu/cpuX/topology/thread_siblings
74 /sys/devices/system/cpu/cpuX/t 75 /sys/devices/system/cpu/cpuX/topology/thread_siblings_list
75 /sys/devices/system/cpu/cpuX/t 76 /sys/devices/system/cpu/cpuX/topology/ppin
76 Date: December 2008 77 Date: December 2008
77 Contact: Linux kernel mailing list <linu 78 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
78 Description: CPU topology files that descri 79 Description: CPU topology files that describe a logical CPU's relationship
79 to other cores and threads in 80 to other cores and threads in the same physical package.
80 81
81 One cpuX directory is created 82 One cpuX directory is created per logical CPU in the system,
82 e.g. /sys/devices/system/cpu/c 83 e.g. /sys/devices/system/cpu/cpu42/.
83 84
84 Briefly, the files above are: 85 Briefly, the files above are:
85 86
>> 87 core_id: the CPU core ID of cpuX. Typically it is the
>> 88 hardware platform's identifier (rather than the kernel's).
>> 89 The actual value is architecture and platform dependent.
>> 90
86 core_siblings: internal kernel 91 core_siblings: internal kernel map of cpuX's hardware threads
87 within the same physical_packa 92 within the same physical_package_id.
88 93
89 core_siblings_list: human-read 94 core_siblings_list: human-readable list of the logical CPU
90 numbers within the same physic 95 numbers within the same physical_package_id as cpuX.
91 96
92 physical_package_id: physical 97 physical_package_id: physical package id of cpuX. Typically
93 corresponds to a physical sock 98 corresponds to a physical socket number, but the actual value
94 is architecture and platform d 99 is architecture and platform dependent.
95 100
96 thread_siblings: internal kern 101 thread_siblings: internal kernel map of cpuX's hardware
97 threads within the same core a 102 threads within the same core as cpuX
98 103
99 thread_siblings_list: human-re 104 thread_siblings_list: human-readable list of cpuX's hardware
100 threads within the same core a 105 threads within the same core as cpuX
101 106
102 ppin: human-readable Protected 107 ppin: human-readable Protected Processor Identification
103 Number of the socket the cpu# 108 Number of the socket the cpu# belongs to. There should be
104 one per physical_package_id. F 109 one per physical_package_id. File is readable only to
105 admin. 110 admin.
106 111
107 See Documentation/admin-guide/ 112 See Documentation/admin-guide/cputopology.rst for more information.
108 113
109 114
110 What: /sys/devices/system/cpu/cpuidl 115 What: /sys/devices/system/cpu/cpuidle/available_governors
111 /sys/devices/system/cpu/cpuidl 116 /sys/devices/system/cpu/cpuidle/current_driver
112 /sys/devices/system/cpu/cpuidl 117 /sys/devices/system/cpu/cpuidle/current_governor
113 /sys/devices/system/cpu/cpuidl 118 /sys/devices/system/cpu/cpuidle/current_governer_ro
114 Date: September 2007 119 Date: September 2007
115 Contact: Linux kernel mailing list <linu 120 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
116 Description: Discover cpuidle policy and me 121 Description: Discover cpuidle policy and mechanism
117 122
118 Various CPUs today support mul 123 Various CPUs today support multiple idle levels that are
119 differentiated by varying exit 124 differentiated by varying exit latencies and power
120 consumption during idle. 125 consumption during idle.
121 126
122 Idle policy (governor) is diff 127 Idle policy (governor) is differentiated from idle mechanism
123 (driver). 128 (driver).
124 129
125 available_governors: (RO) disp 130 available_governors: (RO) displays a space separated list of
126 available governors. 131 available governors.
127 132
128 current_driver: (RO) displays 133 current_driver: (RO) displays current idle mechanism.
129 134
130 current_governor: (RW) display 135 current_governor: (RW) displays current idle policy. Users can
131 switch the governor at runtime 136 switch the governor at runtime by writing to this file.
132 137
133 current_governor_ro: (RO) disp 138 current_governor_ro: (RO) displays current idle policy.
134 139
135 See Documentation/admin-guide/ 140 See Documentation/admin-guide/pm/cpuidle.rst and
136 Documentation/driver-api/pm/cp 141 Documentation/driver-api/pm/cpuidle.rst for more information.
137 142
138 143
139 What: /sys/devices/system/cpu/cpuX/c 144 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/name
140 /sys/devices/system/cpu/cpuX/c 145 /sys/devices/system/cpu/cpuX/cpuidle/stateN/latency
141 /sys/devices/system/cpu/cpuX/c 146 /sys/devices/system/cpu/cpuX/cpuidle/stateN/power
142 /sys/devices/system/cpu/cpuX/c 147 /sys/devices/system/cpu/cpuX/cpuidle/stateN/time
143 /sys/devices/system/cpu/cpuX/c 148 /sys/devices/system/cpu/cpuX/cpuidle/stateN/usage
144 /sys/devices/system/cpu/cpuX/c 149 /sys/devices/system/cpu/cpuX/cpuidle/stateN/above
145 /sys/devices/system/cpu/cpuX/c 150 /sys/devices/system/cpu/cpuX/cpuidle/stateN/below
146 Date: September 2007 151 Date: September 2007
147 KernelVersion: v2.6.24 152 KernelVersion: v2.6.24
148 Contact: Linux power management list <li 153 Contact: Linux power management list <linux-pm@vger.kernel.org>
149 Description: 154 Description:
150 The directory /sys/devices/sys 155 The directory /sys/devices/system/cpu/cpuX/cpuidle contains per
151 logical CPU specific cpuidle i 156 logical CPU specific cpuidle information for each online cpu X.
152 The processor idle states whic 157 The processor idle states which are available for use have the
153 following attributes: 158 following attributes:
154 159
155 ======== ==== ================ 160 ======== ==== =================================================
156 name: (RO) Name of the idle 161 name: (RO) Name of the idle state (string).
157 162
158 latency: (RO) The latency to e 163 latency: (RO) The latency to exit out of this idle state (in
159 microseconds). 164 microseconds).
160 165
161 power: (RO) The power consum 166 power: (RO) The power consumed while in this idle state (in
162 milliwatts). 167 milliwatts).
163 168
164 time: (RO) The total time s 169 time: (RO) The total time spent in this idle state
165 (in microseconds 170 (in microseconds).
166 171
167 usage: (RO) Number of times 172 usage: (RO) Number of times this state was entered (a count).
168 173
169 above: (RO) Number of times 174 above: (RO) Number of times this state was entered, but the
170 observed CPU idl 175 observed CPU idle duration was too short for it
171 (a count). 176 (a count).
172 177
173 below: (RO) Number of times 178 below: (RO) Number of times this state was entered, but the
174 observed CPU idl 179 observed CPU idle duration was too long for it
175 (a count). 180 (a count).
176 ======== ==== ================ 181 ======== ==== =================================================
177 182
178 What: /sys/devices/system/cpu/cpuX/c 183 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/desc
179 Date: February 2008 184 Date: February 2008
180 KernelVersion: v2.6.25 185 KernelVersion: v2.6.25
181 Contact: Linux power management list <li 186 Contact: Linux power management list <linux-pm@vger.kernel.org>
182 Description: 187 Description:
183 (RO) A small description about 188 (RO) A small description about the idle state (string).
184 189
185 190
186 What: /sys/devices/system/cpu/cpuX/c 191 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/disable
187 Date: March 2012 192 Date: March 2012
188 KernelVersion: v3.10 193 KernelVersion: v3.10
189 Contact: Linux power management list <li 194 Contact: Linux power management list <linux-pm@vger.kernel.org>
190 Description: 195 Description:
191 (RW) Option to disable this id 196 (RW) Option to disable this idle state (bool). The behavior and
192 the effect of the disable vari 197 the effect of the disable variable depends on the implementation
193 of a particular governor. In t 198 of a particular governor. In the ladder governor, for example,
194 it is not coherent, i.e. if on 199 it is not coherent, i.e. if one is disabling a light state, then
195 all deeper states are disabled 200 all deeper states are disabled as well, but the disable variable
196 does not reflect it. Likewise, 201 does not reflect it. Likewise, if one enables a deep state but a
197 lighter state still is disable 202 lighter state still is disabled, then this has no effect.
198 203
199 What: /sys/devices/system/cpu/cpuX/c 204 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/default_status
200 Date: December 2019 205 Date: December 2019
201 KernelVersion: v5.6 206 KernelVersion: v5.6
202 Contact: Linux power management list <li 207 Contact: Linux power management list <linux-pm@vger.kernel.org>
203 Description: 208 Description:
204 (RO) The default status of thi 209 (RO) The default status of this state, "enabled" or "disabled".
205 210
206 What: /sys/devices/system/cpu/cpuX/c 211 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/residency
207 Date: March 2014 212 Date: March 2014
208 KernelVersion: v3.15 213 KernelVersion: v3.15
209 Contact: Linux power management list <li 214 Contact: Linux power management list <linux-pm@vger.kernel.org>
210 Description: 215 Description:
211 (RO) Display the target reside 216 (RO) Display the target residency i.e. the minimum amount of
212 time (in microseconds) this cp 217 time (in microseconds) this cpu should spend in this idle state
213 to make the transition worth t 218 to make the transition worth the effort.
214 219
215 What: /sys/devices/system/cpu/cpuX/c 220 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/
216 Date: March 2018 221 Date: March 2018
217 KernelVersion: v4.17 222 KernelVersion: v4.17
218 Contact: Linux power management list <li 223 Contact: Linux power management list <linux-pm@vger.kernel.org>
219 Description: 224 Description:
220 Idle state usage statistics re 225 Idle state usage statistics related to suspend-to-idle.
221 226
222 This attribute group is only p 227 This attribute group is only present for states that can be
223 used in suspend-to-idle with s 228 used in suspend-to-idle with suspended timekeeping.
224 229
225 What: /sys/devices/system/cpu/cpuX/c 230 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/time
226 Date: March 2018 231 Date: March 2018
227 KernelVersion: v4.17 232 KernelVersion: v4.17
228 Contact: Linux power management list <li 233 Contact: Linux power management list <linux-pm@vger.kernel.org>
229 Description: 234 Description:
230 Total time spent by the CPU in 235 Total time spent by the CPU in suspend-to-idle (with scheduler
231 tick suspended) after requesti 236 tick suspended) after requesting this state.
232 237
233 What: /sys/devices/system/cpu/cpuX/c 238 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/usage
234 Date: March 2018 239 Date: March 2018
235 KernelVersion: v4.17 240 KernelVersion: v4.17
236 Contact: Linux power management list <li 241 Contact: Linux power management list <linux-pm@vger.kernel.org>
237 Description: 242 Description:
238 Total number of times this sta 243 Total number of times this state has been requested by the CPU
239 while entering suspend-to-idle 244 while entering suspend-to-idle.
240 245
241 What: /sys/devices/system/cpu/cpuX/c 246 What: /sys/devices/system/cpu/cpuX/cpufreq/*
242 Date: pre-git history 247 Date: pre-git history
243 Contact: linux-pm@vger.kernel.org 248 Contact: linux-pm@vger.kernel.org
244 Description: Discover and change clock spee 249 Description: Discover and change clock speed of CPUs
245 250
246 Clock scaling allows you to ch 251 Clock scaling allows you to change the clock speed of the
247 CPUs on the fly. This is a nic 252 CPUs on the fly. This is a nice method to save battery
248 power, because the lower the c 253 power, because the lower the clock speed, the less power
249 the CPU consumes. 254 the CPU consumes.
250 255
251 There are many knobs to tweak 256 There are many knobs to tweak in this directory.
252 257
253 See files in Documentation/cpu 258 See files in Documentation/cpu-freq/ for more information.
254 259
255 260
256 What: /sys/devices/system/cpu/cpuX/c 261 What: /sys/devices/system/cpu/cpuX/cpufreq/freqdomain_cpus
257 Date: June 2013 262 Date: June 2013
258 Contact: linux-pm@vger.kernel.org 263 Contact: linux-pm@vger.kernel.org
259 Description: Discover CPUs in the same CPU 264 Description: Discover CPUs in the same CPU frequency coordination domain
260 265
261 freqdomain_cpus is the list of 266 freqdomain_cpus is the list of CPUs (online+offline) that share
262 the same clock/freq domain (po 267 the same clock/freq domain (possibly at the hardware level).
263 That information may be hidden 268 That information may be hidden from the cpufreq core and the
264 value of related_cpus may be d 269 value of related_cpus may be different from freqdomain_cpus. This
265 attribute is useful for user s 270 attribute is useful for user space DVFS controllers to get better
266 power/performance results for 271 power/performance results for platforms using acpi-cpufreq.
267 272
268 This file is only present if t 273 This file is only present if the acpi-cpufreq or the cppc-cpufreq
269 drivers are in use. 274 drivers are in use.
270 275
271 276
272 What: /sys/devices/system/cpu/cpu*/c 277 What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
273 Date: August 2008 278 Date: August 2008
274 KernelVersion: 2.6.27 279 KernelVersion: 2.6.27
275 Contact: Linux kernel mailing list <linu 280 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
276 Description: Disable L3 cache indices 281 Description: Disable L3 cache indices
277 282
278 These files exist in every CPU 283 These files exist in every CPU's cache/index3 directory. Each
279 cache_disable_{0,1} file corre 284 cache_disable_{0,1} file corresponds to one disable slot which
280 can be used to disable a cache 285 can be used to disable a cache index. Reading from these files
281 on a processor with this funct 286 on a processor with this functionality will return the currently
282 disabled index for that node. 287 disabled index for that node. There is one L3 structure per
283 node, or per internal node on 288 node, or per internal node on MCM machines. Writing a valid
284 index to one of these files wi 289 index to one of these files will cause the specified cache
285 index to be disabled. 290 index to be disabled.
286 291
287 All AMD processors with L3 cac 292 All AMD processors with L3 caches provide this functionality.
288 For details, see BKDGs at 293 For details, see BKDGs at
289 https://www.amd.com/en/support 294 https://www.amd.com/en/support/tech-docs?keyword=bios+kernel
290 295
291 296
292 What: /sys/devices/system/cpu/cpufre 297 What: /sys/devices/system/cpu/cpufreq/boost
293 Date: August 2012 298 Date: August 2012
294 Contact: Linux kernel mailing list <linu 299 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
295 Description: Processor frequency boosting c 300 Description: Processor frequency boosting control
296 301
297 This switch controls the boost 302 This switch controls the boost setting for the whole system.
298 Boosting allows the CPU and th 303 Boosting allows the CPU and the firmware to run at a frequency
299 beyond its nominal limit. !! 304 beyond it's nominal limit.
300 305
301 More details can be found in 306 More details can be found in
302 Documentation/admin-guide/pm/c 307 Documentation/admin-guide/pm/cpufreq.rst
303 308
304 309
305 What: /sys/devices/system/cpu/cpuX/c 310 What: /sys/devices/system/cpu/cpuX/crash_notes
306 /sys/devices/system/cpu/cpuX/c 311 /sys/devices/system/cpu/cpuX/crash_notes_size
307 Date: April 2013 312 Date: April 2013
308 Contact: kexec@lists.infradead.org 313 Contact: kexec@lists.infradead.org
309 Description: address and size of the percpu 314 Description: address and size of the percpu note.
310 315
311 crash_notes: the physical addr 316 crash_notes: the physical address of the memory that holds the
312 note of cpuX. 317 note of cpuX.
313 318
314 crash_notes_size: size of the 319 crash_notes_size: size of the note of cpuX.
315 320
316 321
317 What: /sys/devices/system/cpu/intel_ 322 What: /sys/devices/system/cpu/intel_pstate/max_perf_pct
318 /sys/devices/system/cpu/intel_ 323 /sys/devices/system/cpu/intel_pstate/min_perf_pct
319 /sys/devices/system/cpu/intel_ 324 /sys/devices/system/cpu/intel_pstate/no_turbo
320 Date: February 2013 325 Date: February 2013
321 Contact: linux-pm@vger.kernel.org 326 Contact: linux-pm@vger.kernel.org
322 Description: Parameters for the Intel P-sta 327 Description: Parameters for the Intel P-state driver
323 328
324 Logic for selecting the curren 329 Logic for selecting the current P-state in Intel
325 Sandybridge+ processors. The t 330 Sandybridge+ processors. The three knobs control
326 limits for the P-state that wi 331 limits for the P-state that will be requested by the
327 driver. 332 driver.
328 333
329 max_perf_pct: limits the maxim 334 max_perf_pct: limits the maximum P state that will be requested by
330 the driver stated as a percent 335 the driver stated as a percentage of the available performance.
331 336
332 min_perf_pct: limits the minim 337 min_perf_pct: limits the minimum P state that will be requested by
333 the driver stated as a percent 338 the driver stated as a percentage of the available performance.
334 339
335 no_turbo: limits the driver to 340 no_turbo: limits the driver to selecting P states below the turbo
336 frequency range. 341 frequency range.
337 342
338 More details can be found in 343 More details can be found in
339 Documentation/admin-guide/pm/i 344 Documentation/admin-guide/pm/intel_pstate.rst
340 345
341 What: /sys/devices/system/cpu/cpu*/c 346 What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below>
342 Date: July 2014(documented, existed 347 Date: July 2014(documented, existed before August 2008)
343 Contact: Sudeep Holla <sudeep.holla@arm. 348 Contact: Sudeep Holla <sudeep.holla@arm.com>
344 Linux kernel mailing list <linu 349 Linux kernel mailing list <linux-kernel@vger.kernel.org>
345 Description: Parameters for the CPU cache a 350 Description: Parameters for the CPU cache attributes
346 351
347 allocation_policy: 352 allocation_policy:
348 - WriteAllocate: 353 - WriteAllocate:
349 alloca 354 allocate a memory location to a cache line
350 on a c 355 on a cache miss because of a write
351 - ReadAllocate: 356 - ReadAllocate:
352 alloca 357 allocate a memory location to a cache line
353 on a c 358 on a cache miss because of a read
354 - ReadWriteAllocate: 359 - ReadWriteAllocate:
355 both w 360 both writeallocate and readallocate
356 361
>> 362 attributes:
>> 363 LEGACY used only on IA64 and is same as write_policy
>> 364
357 coherency_line_size: 365 coherency_line_size:
358 the minim 366 the minimum amount of data in bytes that gets
359 transferr 367 transferred from memory to cache
360 368
361 level: 369 level:
362 the cache hierarchy in 370 the cache hierarchy in the multi-level cache configuration
363 371
364 number_of_sets: 372 number_of_sets:
365 total number o 373 total number of sets in the cache, a set is a
366 collection of 374 collection of cache lines with the same cache index
367 375
368 physical_line_partition: 376 physical_line_partition:
369 number of phys 377 number of physical cache line per cache tag
370 378
371 shared_cpu_list: 379 shared_cpu_list:
372 the list of lo 380 the list of logical cpus sharing the cache
373 381
374 shared_cpu_map: 382 shared_cpu_map:
375 logical cpu ma 383 logical cpu mask containing the list of cpus sharing
376 the cache 384 the cache
377 385
378 size: 386 size:
379 the total cache size i 387 the total cache size in kB
380 388
381 type: 389 type:
382 - Instruction: cache t 390 - Instruction: cache that only holds instructions
383 - Data: cache that onl 391 - Data: cache that only caches data
384 - Unified: cache that 392 - Unified: cache that holds both data and instructions
385 393
386 ways_of_associativity: 394 ways_of_associativity:
387 degree of freedom in p 395 degree of freedom in placing a particular block
388 of memory in the cache 396 of memory in the cache
389 397
390 write_policy: 398 write_policy:
391 - WriteThrough: 399 - WriteThrough:
392 data i 400 data is written to both the cache line
393 and to 401 and to the block in the lower-level memory
394 - WriteBack: 402 - WriteBack:
395 data is w 403 data is written only to the cache line and
396 the modif 404 the modified cache line is written to main
397 memory on 405 memory only when it is replaced
398 406
399 407
400 What: /sys/devices/system/cpu/cpu*/c 408 What: /sys/devices/system/cpu/cpu*/cache/index*/id
401 Date: September 2016 409 Date: September 2016
402 Contact: Linux kernel mailing list <linu 410 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
403 Description: Cache id 411 Description: Cache id
404 412
405 The id provides a unique numbe 413 The id provides a unique number for a specific instance of
406 a cache of a particular type. 414 a cache of a particular type. E.g. there may be a level
407 3 unified cache on each socket 415 3 unified cache on each socket in a server and we may
408 assign them ids 0, 1, 2, ... 416 assign them ids 0, 1, 2, ...
409 417
410 Note that id value can be non- 418 Note that id value can be non-contiguous. E.g. level 1
411 caches typically exist per cor 419 caches typically exist per core, but there may not be a
412 power of two cores on a socket 420 power of two cores on a socket, so these caches may be
413 numbered 0, 1, 2, 3, 4, 5, 8, 421 numbered 0, 1, 2, 3, 4, 5, 8, 9, 10, ...
414 422
415 What: /sys/devices/system/cpu/cpuX/c 423 What: /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats
416 /sys/devices/system/cpu/cpuX/c 424 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/turbo_stat
417 /sys/devices/system/cpu/cpuX/c 425 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/sub_turbo_stat
418 /sys/devices/system/cpu/cpuX/c 426 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/unthrottle
419 /sys/devices/system/cpu/cpuX/c 427 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/powercap
420 /sys/devices/system/cpu/cpuX/c 428 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overtemp
421 /sys/devices/system/cpu/cpuX/c 429 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/supply_fault
422 /sys/devices/system/cpu/cpuX/c 430 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overcurrent
423 /sys/devices/system/cpu/cpuX/c 431 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/occ_reset
424 Date: March 2016 432 Date: March 2016
425 Contact: Linux kernel mailing list <linu 433 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
426 Linux for PowerPC mailing list< !! 434 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
427 Description: POWERNV CPUFreq driver's frequ 435 Description: POWERNV CPUFreq driver's frequency throttle stats directory and
428 attributes 436 attributes
429 437
430 'cpuX/cpufreq/throttle_stats' 438 'cpuX/cpufreq/throttle_stats' directory contains the CPU frequency
431 throttle stat attributes for t 439 throttle stat attributes for the chip. The throttle stats of a cpu
432 is common across all the cpus 440 is common across all the cpus belonging to a chip. Below are the
433 throttle attributes exported i 441 throttle attributes exported in the 'throttle_stats' directory:
434 442
435 - turbo_stat : This file gives 443 - turbo_stat : This file gives the total number of times the max
436 frequency is throttled to lo 444 frequency is throttled to lower frequency in turbo (at and above
437 nominal frequency) range of 445 nominal frequency) range of frequencies.
438 446
439 - sub_turbo_stat : This file g 447 - sub_turbo_stat : This file gives the total number of times the
440 max frequency is throttled t 448 max frequency is throttled to lower frequency in sub-turbo(below
441 nominal frequency) range of 449 nominal frequency) range of frequencies.
442 450
443 - unthrottle : This file gives 451 - unthrottle : This file gives the total number of times the max
444 frequency is unthrottled aft 452 frequency is unthrottled after being throttled.
445 453
446 - powercap : This file gives t 454 - powercap : This file gives the total number of times the max
447 frequency is throttled due t 455 frequency is throttled due to 'Power Capping'.
448 456
449 - overtemp : This file gives t 457 - overtemp : This file gives the total number of times the max
450 frequency is throttled due t 458 frequency is throttled due to 'CPU Over Temperature'.
451 459
452 - supply_fault : This file giv 460 - supply_fault : This file gives the total number of times the
453 max frequency is throttled d 461 max frequency is throttled due to 'Power Supply Failure'.
454 462
455 - overcurrent : This file give 463 - overcurrent : This file gives the total number of times the
456 max frequency is throttled d 464 max frequency is throttled due to 'Overcurrent'.
457 465
458 - occ_reset : This file gives 466 - occ_reset : This file gives the total number of times the max
459 frequency is throttled due t 467 frequency is throttled due to 'OCC Reset'.
460 468
461 The sysfs attributes represent 469 The sysfs attributes representing different throttle reasons like
462 powercap, overtemp, supply_fau 470 powercap, overtemp, supply_fault, overcurrent and occ_reset map to
463 the reasons provided by OCC fi 471 the reasons provided by OCC firmware for throttling the frequency.
464 472
465 What: /sys/devices/system/cpu/cpufre 473 What: /sys/devices/system/cpu/cpufreq/policyX/throttle_stats
466 /sys/devices/system/cpu/cpufre 474 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/turbo_stat
467 /sys/devices/system/cpu/cpufre 475 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/sub_turbo_stat
468 /sys/devices/system/cpu/cpufre 476 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/unthrottle
469 /sys/devices/system/cpu/cpufre 477 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/powercap
470 /sys/devices/system/cpu/cpufre 478 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overtemp
471 /sys/devices/system/cpu/cpufre 479 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/supply_fault
472 /sys/devices/system/cpu/cpufre 480 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overcurrent
473 /sys/devices/system/cpu/cpufre 481 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/occ_reset
474 Date: March 2016 482 Date: March 2016
475 Contact: Linux kernel mailing list <linu 483 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
476 Linux for PowerPC mailing list< !! 484 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
477 Description: POWERNV CPUFreq driver's frequ 485 Description: POWERNV CPUFreq driver's frequency throttle stats directory and
478 attributes 486 attributes
479 487
480 'policyX/throttle_stats' direc 488 'policyX/throttle_stats' directory and all the attributes are same as
481 the /sys/devices/system/cpu/cp 489 the /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats directory and
482 attributes which give the freq 490 attributes which give the frequency throttle information of the chip.
483 491
484 What: /sys/devices/system/cpu/cpuX/r 492 What: /sys/devices/system/cpu/cpuX/regs/
485 /sys/devices/system/cpu/cpuX/r 493 /sys/devices/system/cpu/cpuX/regs/identification/
486 /sys/devices/system/cpu/cpuX/r 494 /sys/devices/system/cpu/cpuX/regs/identification/midr_el1
487 /sys/devices/system/cpu/cpuX/r 495 /sys/devices/system/cpu/cpuX/regs/identification/revidr_el1
488 /sys/devices/system/cpu/cpuX/r <<
489 Date: June 2016 496 Date: June 2016
490 Contact: Linux ARM Kernel Mailing list < 497 Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
491 Description: AArch64 CPU registers 498 Description: AArch64 CPU registers
492 499
493 'identification' directory exp 500 'identification' directory exposes the CPU ID registers for
494 identifying model and revision !! 501 identifying model and revision of the CPU.
495 502
496 What: /sys/devices/system/cpu/aarch3 503 What: /sys/devices/system/cpu/aarch32_el0
497 Date: May 2021 504 Date: May 2021
498 Contact: Linux ARM Kernel Mailing list < 505 Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
499 Description: Identifies the subset of CPUs 506 Description: Identifies the subset of CPUs in the system that can execute
500 AArch32 (32-bit ARM) applicati 507 AArch32 (32-bit ARM) applications. If present, the same format as
501 /sys/devices/system/cpu/{offli 508 /sys/devices/system/cpu/{offline,online,possible,present} is used.
502 If absent, then all or none of 509 If absent, then all or none of the CPUs can execute AArch32
503 applications and execve() will 510 applications and execve() will behave accordingly.
504 511
505 What: /sys/devices/system/cpu/cpuX/c 512 What: /sys/devices/system/cpu/cpuX/cpu_capacity
506 Date: December 2016 513 Date: December 2016
507 Contact: Linux kernel mailing list <linu 514 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
508 Description: information about CPUs heterog 515 Description: information about CPUs heterogeneity.
509 516
510 cpu_capacity: capacity of cpuX 517 cpu_capacity: capacity of cpuX.
511 518
512 What: /sys/devices/system/cpu/vulner 519 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 520 /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 521 /sys/devices/system/cpu/vulnerabilities/spectre_v1
523 /sys/devices/system/cpu/vulner 522 /sys/devices/system/cpu/vulnerabilities/spectre_v2
>> 523 /sys/devices/system/cpu/vulnerabilities/spec_store_bypass
>> 524 /sys/devices/system/cpu/vulnerabilities/l1tf
>> 525 /sys/devices/system/cpu/vulnerabilities/mds
524 /sys/devices/system/cpu/vulner 526 /sys/devices/system/cpu/vulnerabilities/srbds
525 /sys/devices/system/cpu/vulner 527 /sys/devices/system/cpu/vulnerabilities/tsx_async_abort
>> 528 /sys/devices/system/cpu/vulnerabilities/itlb_multihit
>> 529 /sys/devices/system/cpu/vulnerabilities/mmio_stale_data
>> 530 /sys/devices/system/cpu/vulnerabilities/retbleed
526 Date: January 2018 531 Date: January 2018
527 Contact: Linux kernel mailing list <linu 532 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
528 Description: Information about CPU vulnerab 533 Description: Information about CPU vulnerabilities
529 534
530 The files are named after the 535 The files are named after the code names of CPU
531 vulnerabilities. The output of 536 vulnerabilities. The output of those files reflects the
532 state of the CPUs in the syste 537 state of the CPUs in the system. Possible output values:
533 538
534 ================ ============ 539 ================ ==============================================
535 "Not affected" CPU is not a 540 "Not affected" CPU is not affected by the vulnerability
536 "Vulnerable" CPU is affec 541 "Vulnerable" CPU is affected and no mitigation in effect
537 "Mitigation: $M" CPU is affec 542 "Mitigation: $M" CPU is affected and mitigation $M is in effect
538 ================ ============ 543 ================ ==============================================
539 544
540 See also: Documentation/admin- 545 See also: Documentation/admin-guide/hw-vuln/index.rst
541 546
542 What: /sys/devices/system/cpu/smt 547 What: /sys/devices/system/cpu/smt
543 /sys/devices/system/cpu/smt/ac 548 /sys/devices/system/cpu/smt/active
544 /sys/devices/system/cpu/smt/co 549 /sys/devices/system/cpu/smt/control
545 Date: June 2018 550 Date: June 2018
546 Contact: Linux kernel mailing list <linu 551 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
547 Description: Control Symmetric Multi Thread 552 Description: Control Symmetric Multi Threading (SMT)
548 553
549 active: Tells whether SMT is 554 active: Tells whether SMT is active (enabled and siblings online)
550 555
551 control: Read/write interface 556 control: Read/write interface to control SMT. Possible
552 values: 557 values:
553 558
554 ================ ==== 559 ================ =========================================
555 "on" SMT 560 "on" SMT is enabled
556 "off" SMT 561 "off" SMT is disabled
557 "<N>" SMT <<
558 "forceoff" SMT 562 "forceoff" SMT is force disabled. Cannot be changed.
559 "notsupported" SMT 563 "notsupported" SMT is not supported by the CPU
560 "notimplemented" SMT 564 "notimplemented" SMT runtime toggling is not
561 impl 565 implemented for the architecture
562 ================ ==== 566 ================ =========================================
563 567
564 If control status is 568 If control status is "forceoff" or "notsupported" writes
565 are rejected. Note th !! 569 are rejected.
566 offline cores. <<
567 570
568 What: /sys/devices/system/cpu/cpuX/p 571 What: /sys/devices/system/cpu/cpuX/power/energy_perf_bias
569 Date: March 2019 572 Date: March 2019
570 Contact: linux-pm@vger.kernel.org 573 Contact: linux-pm@vger.kernel.org
571 Description: Intel Energy and Performance B 574 Description: Intel Energy and Performance Bias Hint (EPB)
572 575
573 EPB for the given CPU in a sli 576 EPB for the given CPU in a sliding scale 0 - 15, where a value
574 of 0 corresponds to a hint pre 577 of 0 corresponds to a hint preference for highest performance
575 and a value of 15 corresponds 578 and a value of 15 corresponds to the maximum energy savings.
576 579
577 In order to change the EPB val 580 In order to change the EPB value for the CPU, write either
578 a number in the 0 - 15 sliding 581 a number in the 0 - 15 sliding scale above, or one of the
579 strings: "performance", "balan 582 strings: "performance", "balance-performance", "normal",
580 "balance-power", "power" (that 583 "balance-power", "power" (that represent values reflected by
581 their meaning), to this attrib 584 their meaning), to this attribute.
582 585
583 This attribute is present for 586 This attribute is present for all online CPUs supporting the
584 Intel EPB feature. 587 Intel EPB feature.
585 588
586 What: /sys/devices/system/cpu/umwait 589 What: /sys/devices/system/cpu/umwait_control
587 /sys/devices/system/cpu/umwait 590 /sys/devices/system/cpu/umwait_control/enable_c02
588 /sys/devices/system/cpu/umwait 591 /sys/devices/system/cpu/umwait_control/max_time
589 Date: May 2019 592 Date: May 2019
590 Contact: Linux kernel mailing list <linu 593 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
591 Description: Umwait control 594 Description: Umwait control
592 595
593 enable_c02: Read/write interfa 596 enable_c02: Read/write interface to control umwait C0.2 state
594 Read returns C0.2 stat 597 Read returns C0.2 state status:
595 0: C0.2 is dis 598 0: C0.2 is disabled
596 1: C0.2 is ena 599 1: C0.2 is enabled
597 600
598 Write 'y' or '1' or ' 601 Write 'y' or '1' or 'on' to enable C0.2 state.
599 Write 'n' or '0' or ' 602 Write 'n' or '0' or 'off' to disable C0.2 state.
600 603
601 The interface is case 604 The interface is case insensitive.
602 605
603 max_time: Read/write interface 606 max_time: Read/write interface to control umwait maximum time
604 in TSC-quanta that t 607 in TSC-quanta that the CPU can reside in either C0.1
605 or C0.2 state. The t 608 or C0.2 state. The time is an unsigned 32-bit number.
606 Note that a value of 609 Note that a value of zero means there is no limit.
607 Low order two bits m 610 Low order two bits must be zero.
608 611
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 612 What: /sys/devices/system/cpu/svm
622 Date: August 2019 613 Date: August 2019
623 Contact: Linux kernel mailing list <linu 614 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
624 Linux for PowerPC mailing list< !! 615 Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
625 Description: Secure Virtual Machine 616 Description: Secure Virtual Machine
626 617
627 If 1, it means the system is u 618 If 1, it means the system is using the Protected Execution
628 Facility in POWER9 and newer p 619 Facility in POWER9 and newer processors. i.e., it is a Secure
629 Virtual Machine. 620 Virtual Machine.
630 621
631 What: /sys/devices/system/cpu/cpuX/p 622 What: /sys/devices/system/cpu/cpuX/purr
632 Date: Apr 2005 623 Date: Apr 2005
633 Contact: Linux for PowerPC mailing list< !! 624 Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
634 Description: PURR ticks for this CPU since 625 Description: PURR ticks for this CPU since the system boot.
635 626
636 The Processor Utilization Reso 627 The Processor Utilization Resources Register (PURR) is
637 a 64-bit counter which provide 628 a 64-bit counter which provides an estimate of the
638 resources used by the CPU thre 629 resources used by the CPU thread. The contents of this
639 register increases monotonical 630 register increases monotonically. This sysfs interface
640 exposes the number of PURR tic 631 exposes the number of PURR ticks for cpuX.
641 632
642 What: /sys/devices/system/cpu/cpuX/s 633 What: /sys/devices/system/cpu/cpuX/spurr
643 Date: Dec 2006 634 Date: Dec 2006
644 Contact: Linux for PowerPC mailing list< !! 635 Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
645 Description: SPURR ticks for this CPU since 636 Description: SPURR ticks for this CPU since the system boot.
646 637
647 The Scaled Processor Utilizati 638 The Scaled Processor Utilization Resources Register
648 (SPURR) is a 64-bit counter th 639 (SPURR) is a 64-bit counter that provides a frequency
649 invariant estimate of the reso 640 invariant estimate of the resources used by the CPU
650 thread. The contents of this r 641 thread. The contents of this register increases
651 monotonically. This sysfs inte 642 monotonically. This sysfs interface exposes the number
652 of SPURR ticks for cpuX. 643 of SPURR ticks for cpuX.
653 644
654 What: /sys/devices/system/cpu/cpuX/i 645 What: /sys/devices/system/cpu/cpuX/idle_purr
655 Date: Apr 2020 646 Date: Apr 2020
656 Contact: Linux for PowerPC mailing list< !! 647 Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
657 Description: PURR ticks for cpuX when it wa 648 Description: PURR ticks for cpuX when it was idle.
658 649
659 This sysfs interface exposes t 650 This sysfs interface exposes the number of PURR ticks
660 for cpuX when it was idle. 651 for cpuX when it was idle.
661 652
662 What: /sys/devices/system/cpu/cpuX/i 653 What: /sys/devices/system/cpu/cpuX/idle_spurr
663 Date: Apr 2020 654 Date: Apr 2020
664 Contact: Linux for PowerPC mailing list< !! 655 Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
665 Description: SPURR ticks for cpuX when it w 656 Description: SPURR ticks for cpuX when it was idle.
666 657
667 This sysfs interface exposes t 658 This sysfs interface exposes the number of SPURR ticks
668 for cpuX when it was idle. 659 for cpuX when it was idle.
669 660
670 What: /sys/devices/system/cpu/cpuX/m 661 What: /sys/devices/system/cpu/cpuX/mte_tcf_preferred
671 Date: July 2021 662 Date: July 2021
672 Contact: Linux ARM Kernel Mailing list < 663 Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
673 Description: Preferred MTE tag checking mod 664 Description: Preferred MTE tag checking mode
674 665
675 When a user program specifies 666 When a user program specifies more than one MTE tag checking
676 mode, this sysfs node is used 667 mode, this sysfs node is used to specify which mode should
677 be preferred when scheduling a 668 be preferred when scheduling a task on that CPU. Possible
678 values: 669 values:
679 670
680 ================ ============ 671 ================ ==============================================
681 "sync" Prefer synch 672 "sync" Prefer synchronous mode
682 "asymm" Prefer asymm 673 "asymm" Prefer asymmetric mode
683 "async" Prefer async 674 "async" Prefer asynchronous mode
684 ================ ============ 675 ================ ==============================================
685 676
686 See also: Documentation/arch/a !! 677 See also: Documentation/arm64/memory-tagging-extension.rst
687 678
688 What: /sys/devices/system/cpu/nohz_f 679 What: /sys/devices/system/cpu/nohz_full
689 Date: Apr 2015 680 Date: Apr 2015
690 Contact: Linux kernel mailing list <linu 681 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
691 Description: 682 Description:
692 (RO) the list of CPUs that are 683 (RO) the list of CPUs that are in nohz_full mode.
693 These CPUs are set by boot par 684 These CPUs are set by boot parameter "nohz_full=".
694 685
695 What: /sys/devices/system/cpu/isolat 686 What: /sys/devices/system/cpu/isolated
696 Date: Apr 2015 687 Date: Apr 2015
697 Contact: Linux kernel mailing list <linu 688 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
698 Description: 689 Description:
699 (RO) the list of CPUs that are 690 (RO) the list of CPUs that are isolated and don't
700 participate in load balancing. 691 participate in load balancing. These CPUs are set by
701 boot parameter "isolcpus=". 692 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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