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