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1What: /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
12What: /sys/devices/system/cpu/sched_mc_power_savings
13 /sys/devices/system/cpu/sched_smt_power_savings
14Date: June 2006
15Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
16Description: Discover and adjust the kernel's multi-core scheduler support.
17
18 Possible values are:
19
20 0 - No power saving load balance (default value)
21 1 - Fill one thread/core/package first for long running threads
22 2 - Also bias task wakeups to semi-idle cpu package for power
23 savings
24
25 sched_mc_power_savings is dependent upon SCHED_MC, which is
26 itself architecture dependent.
27
28 sched_smt_power_savings is dependent upon SCHED_SMT, which
29 is itself architecture dependent.
30
31 The two files are independent of each other. It is possible
32 that one file may be present without the other.
33
34 Introduced by git commit 5c45bf27.
35
36
37What: /sys/devices/system/cpu/kernel_max
38 /sys/devices/system/cpu/offline
39 /sys/devices/system/cpu/online
40 /sys/devices/system/cpu/possible
41 /sys/devices/system/cpu/present
42Date: December 2008
43Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
44Description: CPU topology files that describe kernel limits related to
45 hotplug. Briefly:
46
47 kernel_max: the maximum cpu index allowed by the kernel
48 configuration.
49
50 offline: cpus that are not online because they have been
51 HOTPLUGGED off or exceed the limit of cpus allowed by the
52 kernel configuration (kernel_max above).
53
54 online: cpus that are online and being scheduled.
55
56 possible: cpus that have been allocated resources and can be
57 brought online if they are present.
58
59 present: cpus that have been identified as being present in
60 the system.
61
62 See Documentation/cputopology.txt for more information.
63
64
65What: /sys/devices/system/cpu/probe
66 /sys/devices/system/cpu/release
67Date: November 2009
68Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
69Description: Dynamic addition and removal of CPU's. This is not hotplug
70 removal, this is meant complete removal/addition of the CPU
71 from the system.
72
73 probe: writes to this file will dynamically add a CPU to the
74 system. Information written to the file to add CPU's is
75 architecture specific.
76
77 release: writes to this file dynamically remove a CPU from
78 the system. Information writtento the file to remove CPU's
79 is architecture specific.
80
81What: /sys/devices/system/cpu/cpu#/node
82Date: October 2009
83Contact: Linux memory management mailing list <linux-mm@kvack.org>
84Description: Discover NUMA node a CPU belongs to
85
86 When CONFIG_NUMA is enabled, a symbolic link that points
87 to the corresponding NUMA node directory.
88
89 For example, the following symlink is created for cpu42
90 in NUMA node 2:
91
92 /sys/devices/system/cpu/cpu42/node2 -> ../../node/node2
93
94
95What: /sys/devices/system/cpu/cpu#/node
96Date: October 2009
97Contact: Linux memory management mailing list <linux-mm@kvack.org>
98Description: Discover NUMA node a CPU belongs to
99
100 When CONFIG_NUMA is enabled, a symbolic link that points
101 to the corresponding NUMA node directory.
102
103 For example, the following symlink is created for cpu42
104 in NUMA node 2:
105
106 /sys/devices/system/cpu/cpu42/node2 -> ../../node/node2
107
108
109What: /sys/devices/system/cpu/cpu#/topology/core_id
110 /sys/devices/system/cpu/cpu#/topology/core_siblings
111 /sys/devices/system/cpu/cpu#/topology/core_siblings_list
112 /sys/devices/system/cpu/cpu#/topology/physical_package_id
113 /sys/devices/system/cpu/cpu#/topology/thread_siblings
114 /sys/devices/system/cpu/cpu#/topology/thread_siblings_list
115Date: December 2008
116Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
117Description: CPU topology files that describe a logical CPU's relationship
118 to other cores and threads in the same physical package.
119
120 One cpu# directory is created per logical CPU in the system,
121 e.g. /sys/devices/system/cpu/cpu42/.
122
123 Briefly, the files above are:
124
125 core_id: the CPU core ID of cpu#. Typically it is the
126 hardware platform's identifier (rather than the kernel's).
127 The actual value is architecture and platform dependent.
128
129 core_siblings: internal kernel map of cpu#'s hardware threads
130 within the same physical_package_id.
131
132 core_siblings_list: human-readable list of the logical CPU
133 numbers within the same physical_package_id as cpu#.
134
135 physical_package_id: physical package id of cpu#. Typically
136 corresponds to a physical socket number, but the actual value
137 is architecture and platform dependent.
138
139 thread_siblings: internel kernel map of cpu#'s hardware
140 threads within the same core as cpu#
141
142 thread_siblings_list: human-readable list of cpu#'s hardware
143 threads within the same core as cpu#
144
145 See Documentation/cputopology.txt for more information.
146
147
148What: /sys/devices/system/cpu/cpuidle/current_driver
149 /sys/devices/system/cpu/cpuidle/current_governer_ro
150Date: September 2007
151Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
152Description: Discover cpuidle policy and mechanism
153
154 Various CPUs today support multiple idle levels that are
155 differentiated by varying exit latencies and power
156 consumption during idle.
157
158 Idle policy (governor) is differentiated from idle mechanism
159 (driver)
160
161 current_driver: displays current idle mechanism
162
163 current_governor_ro: displays current idle policy
164
165 See files in Documentation/cpuidle/ for more information.
166
167
168What: /sys/devices/system/cpu/cpu#/cpufreq/*
169Date: pre-git history
170Contact: cpufreq@vger.kernel.org
171Description: Discover and change clock speed of CPUs
172
173 Clock scaling allows you to change the clock speed of the
174 CPUs on the fly. This is a nice method to save battery
175 power, because the lower the clock speed, the less power
176 the CPU consumes.
177
178 There are many knobs to tweak in this directory.
179
180 See files in Documentation/cpu-freq/ for more information.
181
182 In particular, read Documentation/cpu-freq/user-guide.txt
183 to learn how to control the knobs.
184
185
186What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
187Date: August 2008
188KernelVersion: 2.6.27
189Contact: discuss@x86-64.org
190Description: Disable L3 cache indices
191
192 These files exist in every CPU's cache/index3 directory. Each
193 cache_disable_{0,1} file corresponds to one disable slot which
194 can be used to disable a cache index. Reading from these files
195 on a processor with this functionality will return the currently
196 disabled index for that node. There is one L3 structure per
197 node, or per internal node on MCM machines. Writing a valid
198 index to one of these files will cause the specificed cache
199 index to be disabled.
200
201 All AMD processors with L3 caches provide this functionality.
202 For details, see BKDGs at
203 http://developer.amd.com/documentation/guides/Pages/default.aspx
1What: /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
12What: /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
40What: /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.
55
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
70What: /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
109What: /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
129What: /sys/devices/system/cpu/cpu#/cpufreq/*
130Date: pre-git history
131Contact: cpufreq@vger.kernel.org
132Description: 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
147What: /sys/devices/system/cpu/cpu#/cpufreq/freqdomain_cpus
148Date: June 2013
149Contact: cpufreq@vger.kernel.org
150Description: 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
162What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
163Date: August 2008
164KernelVersion: 2.6.27
165Contact: discuss@x86-64.org
166Description: Disable L3 cache indices
167
168 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
180
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
191
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#.
203
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