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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 Chiangcba5dd72009-12-14 17:59:09 -080070What: /sys/devices/system/cpu/cpu#/node
71Date: October 2009
72Contact: Linux memory management mailing list <linux-mm@kvack.org>
73Description: Discover NUMA node a CPU belongs to
74
75 When CONFIG_NUMA is enabled, a symbolic link that points
76 to the corresponding NUMA node directory.
77
78 For example, the following symlink is created for cpu42
79 in NUMA node 2:
80
81 /sys/devices/system/cpu/cpu42/node2 -> ../../node/node2
82
83
Alex Chiang663fb2f2009-10-21 21:45:31 -060084What: /sys/devices/system/cpu/cpu#/topology/core_id
85 /sys/devices/system/cpu/cpu#/topology/core_siblings
86 /sys/devices/system/cpu/cpu#/topology/core_siblings_list
87 /sys/devices/system/cpu/cpu#/topology/physical_package_id
88 /sys/devices/system/cpu/cpu#/topology/thread_siblings
89 /sys/devices/system/cpu/cpu#/topology/thread_siblings_list
90Date: December 2008
91Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
92Description: CPU topology files that describe a logical CPU's relationship
93 to other cores and threads in the same physical package.
94
95 One cpu# directory is created per logical CPU in the system,
96 e.g. /sys/devices/system/cpu/cpu42/.
97
98 Briefly, the files above are:
99
100 core_id: the CPU core ID of cpu#. Typically it is the
101 hardware platform's identifier (rather than the kernel's).
102 The actual value is architecture and platform dependent.
103
104 core_siblings: internal kernel map of cpu#'s hardware threads
105 within the same physical_package_id.
106
107 core_siblings_list: human-readable list of the logical CPU
108 numbers within the same physical_package_id as cpu#.
109
110 physical_package_id: physical package id of cpu#. Typically
111 corresponds to a physical socket number, but the actual value
112 is architecture and platform dependent.
113
114 thread_siblings: internel kernel map of cpu#'s hardware
115 threads within the same core as cpu#
116
117 thread_siblings_list: human-readable list of cpu#'s hardware
118 threads within the same core as cpu#
119
120 See Documentation/cputopology.txt for more information.
121
122
Alex Chiangc1fb5c42009-10-21 21:45:41 -0600123What: /sys/devices/system/cpu/cpuidle/current_driver
124 /sys/devices/system/cpu/cpuidle/current_governer_ro
125Date: September 2007
126Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
127Description: Discover cpuidle policy and mechanism
128
129 Various CPUs today support multiple idle levels that are
130 differentiated by varying exit latencies and power
131 consumption during idle.
132
133 Idle policy (governor) is differentiated from idle mechanism
134 (driver)
135
136 current_driver: displays current idle mechanism
137
138 current_governor_ro: displays current idle policy
139
140 See files in Documentation/cpuidle/ for more information.
141
142
Alex Chiang0cda8b92009-10-21 21:45:46 -0600143What: /sys/devices/system/cpu/cpu#/cpufreq/*
144Date: pre-git history
145Contact: cpufreq@vger.kernel.org
146Description: Discover and change clock speed of CPUs
147
148 Clock scaling allows you to change the clock speed of the
149 CPUs on the fly. This is a nice method to save battery
150 power, because the lower the clock speed, the less power
151 the CPU consumes.
152
153 There are many knobs to tweak in this directory.
154
155 See files in Documentation/cpu-freq/ for more information.
156
157 In particular, read Documentation/cpu-freq/user-guide.txt
158 to learn how to control the knobs.
159
160
Borislav Petkoveecaaba2011-05-16 15:39:48 +0200161What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
162Date: August 2008
Mark Langsdorf2fad2d92009-04-09 15:31:53 +0200163KernelVersion: 2.6.27
Borislav Petkoveecaaba2011-05-16 15:39:48 +0200164Contact: discuss@x86-64.org
165Description: Disable L3 cache indices
Mark Langsdorf2fad2d92009-04-09 15:31:53 +0200166
Borislav Petkoveecaaba2011-05-16 15:39:48 +0200167 These files exist in every CPU's cache/index3 directory. Each
168 cache_disable_{0,1} file corresponds to one disable slot which
169 can be used to disable a cache index. Reading from these files
170 on a processor with this functionality will return the currently
171 disabled index for that node. There is one L3 structure per
172 node, or per internal node on MCM machines. Writing a valid
173 index to one of these files will cause the specificed cache
174 index to be disabled.
175
176 All AMD processors with L3 caches provide this functionality.
177 For details, see BKDGs at
178 http://developer.amd.com/documentation/guides/Pages/default.aspx
Andre Przywara615b7302012-09-04 08:28:07 +0000179
180
181What: /sys/devices/system/cpu/cpufreq/boost
182Date: August 2012
183Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
184Description: Processor frequency boosting control
185
186 This switch controls the boost setting for the whole system.
187 Boosting allows the CPU and the firmware to run at a frequency
188 beyound it's nominal limit.
189 More details can be found in Documentation/cpu-freq/boost.txt