blob: 99983e67c13c9f6aadff74c1969a4d27cede7d26 [file] [log] [blame]
Alex Chiang2ceb3fb2009-10-21 21:45:20 -06001What: /sys/devices/system/cpu/
2Date: pre-git history
3Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
4Description:
5 A collection of both global and individual CPU attributes
6
7 Individual CPU attributes are contained in subdirectories
8 named by the kernel's logical CPU number, e.g.:
9
10 /sys/devices/system/cpu/cpu#/
11
Alex Chiangd93fc862009-10-21 21:45:25 -060012What: /sys/devices/system/cpu/kernel_max
13 /sys/devices/system/cpu/offline
14 /sys/devices/system/cpu/online
15 /sys/devices/system/cpu/possible
16 /sys/devices/system/cpu/present
17Date: December 2008
18Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
19Description: CPU topology files that describe kernel limits related to
20 hotplug. Briefly:
21
22 kernel_max: the maximum cpu index allowed by the kernel
23 configuration.
24
25 offline: cpus that are not online because they have been
26 HOTPLUGGED off or exceed the limit of cpus allowed by the
27 kernel configuration (kernel_max above).
28
29 online: cpus that are online and being scheduled.
30
31 possible: cpus that have been allocated resources and can be
32 brought online if they are present.
33
34 present: cpus that have been identified as being present in
35 the system.
36
37 See Documentation/cputopology.txt for more information.
38
39
Nathan Fontenot12633e82009-11-25 17:23:25 +000040What: /sys/devices/system/cpu/probe
41 /sys/devices/system/cpu/release
42Date: November 2009
43Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
44Description: Dynamic addition and removal of CPU's. This is not hotplug
45 removal, this is meant complete removal/addition of the CPU
46 from the system.
47
48 probe: writes to this file will dynamically add a CPU to the
49 system. Information written to the file to add CPU's is
50 architecture specific.
51
52 release: writes to this file dynamically remove a CPU from
53 the system. Information writtento the file to remove CPU's
54 is architecture specific.
Alex Chiang657348a2009-10-21 22:15:30 -060055
56What: /sys/devices/system/cpu/cpu#/node
57Date: October 2009
58Contact: Linux memory management mailing list <linux-mm@kvack.org>
59Description: Discover NUMA node a CPU belongs to
60
61 When CONFIG_NUMA is enabled, a symbolic link that points
62 to the corresponding NUMA node directory.
63
64 For example, the following symlink is created for cpu42
65 in NUMA node 2:
66
67 /sys/devices/system/cpu/cpu42/node2 -> ../../node/node2
68
69
Alex Chiang663fb2f2009-10-21 21:45:31 -060070What: /sys/devices/system/cpu/cpu#/topology/core_id
71 /sys/devices/system/cpu/cpu#/topology/core_siblings
72 /sys/devices/system/cpu/cpu#/topology/core_siblings_list
73 /sys/devices/system/cpu/cpu#/topology/physical_package_id
74 /sys/devices/system/cpu/cpu#/topology/thread_siblings
75 /sys/devices/system/cpu/cpu#/topology/thread_siblings_list
76Date: December 2008
77Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
78Description: CPU topology files that describe a logical CPU's relationship
79 to other cores and threads in the same physical package.
80
81 One cpu# directory is created per logical CPU in the system,
82 e.g. /sys/devices/system/cpu/cpu42/.
83
84 Briefly, the files above are:
85
86 core_id: the CPU core ID of cpu#. Typically it is the
87 hardware platform's identifier (rather than the kernel's).
88 The actual value is architecture and platform dependent.
89
90 core_siblings: internal kernel map of cpu#'s hardware threads
91 within the same physical_package_id.
92
93 core_siblings_list: human-readable list of the logical CPU
94 numbers within the same physical_package_id as cpu#.
95
96 physical_package_id: physical package id of cpu#. Typically
97 corresponds to a physical socket number, but the actual value
98 is architecture and platform dependent.
99
100 thread_siblings: internel kernel map of cpu#'s hardware
101 threads within the same core as cpu#
102
103 thread_siblings_list: human-readable list of cpu#'s hardware
104 threads within the same core as cpu#
105
106 See Documentation/cputopology.txt for more information.
107
108
Alex Chiangc1fb5c42009-10-21 21:45:41 -0600109What: /sys/devices/system/cpu/cpuidle/current_driver
110 /sys/devices/system/cpu/cpuidle/current_governer_ro
111Date: September 2007
112Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
113Description: Discover cpuidle policy and mechanism
114
115 Various CPUs today support multiple idle levels that are
116 differentiated by varying exit latencies and power
117 consumption during idle.
118
119 Idle policy (governor) is differentiated from idle mechanism
120 (driver)
121
122 current_driver: displays current idle mechanism
123
124 current_governor_ro: displays current idle policy
125
126 See files in Documentation/cpuidle/ for more information.
127
128
Alex Chiang0cda8b92009-10-21 21:45:46 -0600129What: /sys/devices/system/cpu/cpu#/cpufreq/*
130Date: pre-git history
Viresh Kumardec102a2014-04-22 10:42:05 +0530131Contact: linux-pm@vger.kernel.org
Alex Chiang0cda8b92009-10-21 21:45:46 -0600132Description: Discover and change clock speed of CPUs
133
134 Clock scaling allows you to change the clock speed of the
135 CPUs on the fly. This is a nice method to save battery
136 power, because the lower the clock speed, the less power
137 the CPU consumes.
138
139 There are many knobs to tweak in this directory.
140
141 See files in Documentation/cpu-freq/ for more information.
142
143 In particular, read Documentation/cpu-freq/user-guide.txt
144 to learn how to control the knobs.
145
146
Lan Tianyuf4fd3792013-06-27 15:08:54 +0800147What: /sys/devices/system/cpu/cpu#/cpufreq/freqdomain_cpus
148Date: June 2013
Viresh Kumardec102a2014-04-22 10:42:05 +0530149Contact: linux-pm@vger.kernel.org
Lan Tianyuf4fd3792013-06-27 15:08:54 +0800150Description: Discover CPUs in the same CPU frequency coordination domain
151
152 freqdomain_cpus is the list of CPUs (online+offline) that share
153 the same clock/freq domain (possibly at the hardware level).
154 That information may be hidden from the cpufreq core and the
155 value of related_cpus may be different from freqdomain_cpus. This
156 attribute is useful for user space DVFS controllers to get better
157 power/performance results for platforms using acpi-cpufreq.
158
159 This file is only present if the acpi-cpufreq driver is in use.
160
161
Borislav Petkoveecaaba2011-05-16 15:39:48 +0200162What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
163Date: August 2008
Mark Langsdorf2fad2d92009-04-09 15:31:53 +0200164KernelVersion: 2.6.27
Borislav Petkoveecaaba2011-05-16 15:39:48 +0200165Contact: discuss@x86-64.org
166Description: Disable L3 cache indices
Mark Langsdorf2fad2d92009-04-09 15:31:53 +0200167
Borislav Petkoveecaaba2011-05-16 15:39:48 +0200168 These files exist in every CPU's cache/index3 directory. Each
169 cache_disable_{0,1} file corresponds to one disable slot which
170 can be used to disable a cache index. Reading from these files
171 on a processor with this functionality will return the currently
172 disabled index for that node. There is one L3 structure per
173 node, or per internal node on MCM machines. Writing a valid
174 index to one of these files will cause the specificed cache
175 index to be disabled.
176
177 All AMD processors with L3 caches provide this functionality.
178 For details, see BKDGs at
179 http://developer.amd.com/documentation/guides/Pages/default.aspx
Andre Przywara615b7302012-09-04 08:28:07 +0000180
181
182What: /sys/devices/system/cpu/cpufreq/boost
183Date: August 2012
184Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
185Description: Processor frequency boosting control
186
187 This switch controls the boost setting for the whole system.
188 Boosting allows the CPU and the firmware to run at a frequency
189 beyound it's nominal limit.
190 More details can be found in Documentation/cpu-freq/boost.txt
Zhang Yanfeic4fd6752013-03-28 16:16:45 +0800191
192
193What: /sys/devices/system/cpu/cpu#/crash_notes
194 /sys/devices/system/cpu/cpu#/crash_notes_size
195Date: April 2013
196Contact: kexec@lists.infradead.org
197Description: address and size of the percpu note.
198
199 crash_notes: the physical address of the memory that holds the
200 note of cpu#.
201
202 crash_notes_size: size of the note of cpu#.
Ramkumar Ramachandrafbe299e2014-01-06 18:24:26 +0530203
204
205What: /sys/devices/system/cpu/intel_pstate/max_perf_pct
206 /sys/devices/system/cpu/intel_pstate/min_perf_pct
207 /sys/devices/system/cpu/intel_pstate/no_turbo
208Date: February 2013
209Contact: linux-pm@vger.kernel.org
210Description: Parameters for the Intel P-state driver
211
212 Logic for selecting the current P-state in Intel
213 Sandybridge+ processors. The three knobs control
214 limits for the P-state that will be requested by the
215 driver.
216
217 max_perf_pct: limits the maximum P state that will be requested by
218 the driver stated as a percentage of the available performance.
219
220 min_perf_pct: limits the minimum P state that will be requested by
221 the driver stated as a percentage of the available performance.
222
223 no_turbo: limits the driver to selecting P states below the turbo
224 frequency range.
225
226 More details can be found in Documentation/cpu-freq/intel-pstate.txt
Sudeep Holla246246c2014-09-30 14:48:25 +0100227
228What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below>
229Date: July 2014(documented, existed before August 2008)
230Contact: Sudeep Holla <sudeep.holla@arm.com>
231 Linux kernel mailing list <linux-kernel@vger.kernel.org>
232Description: Parameters for the CPU cache attributes
233
234 allocation_policy:
235 - WriteAllocate: allocate a memory location to a cache line
236 on a cache miss because of a write
237 - ReadAllocate: allocate a memory location to a cache line
238 on a cache miss because of a read
239 - ReadWriteAllocate: both writeallocate and readallocate
240
241 attributes: LEGACY used only on IA64 and is same as write_policy
242
243 coherency_line_size: the minimum amount of data in bytes that gets
244 transferred from memory to cache
245
246 level: the cache hierarcy in the multi-level cache configuration
247
248 number_of_sets: total number of sets in the cache, a set is a
249 collection of cache lines with the same cache index
250
251 physical_line_partition: number of physical cache line per cache tag
252
253 shared_cpu_list: the list of logical cpus sharing the cache
254
255 shared_cpu_map: logical cpu mask containing the list of cpus sharing
256 the cache
257
258 size: the total cache size in kB
259
260 type:
261 - Instruction: cache that only holds instructions
262 - Data: cache that only caches data
263 - Unified: cache that holds both data and instructions
264
265 ways_of_associativity: degree of freedom in placing a particular block
266 of memory in the cache
267
268 write_policy:
269 - WriteThrough: data is written to both the cache line
270 and to the block in the lower-level memory
271 - WriteBack: data is written only to the cache line and
272 the modified cache line is written to main
273 memory only when it is replaced