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cpufreq: make sure frequency transitions are serialized
[linux-2.6-block.git] / Documentation / ABI / testing / sysfs-devices-system-cpu
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2ceb3fb0
AC		 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
d93fc863
AC		 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
12633e80
NF		 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.
657348a0 55
cba5dd7f
AC		 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
663fb2fc
AC		 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
c1fb5c47
AC		 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
0cda8b91
AC		 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
eecaaba5
BP		 147What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
148Date: August 2008
2fad2d9b 149KernelVersion: 2.6.27
eecaaba5
BP		 150Contact: discuss@x86-64.org
151Description: Disable L3 cache indices
152
153 These files exist in every CPU's cache/index3 directory. Each
154 cache_disable_{0,1} file corresponds to one disable slot which
155 can be used to disable a cache index. Reading from these files
156 on a processor with this functionality will return the currently
157 disabled index for that node. There is one L3 structure per
158 node, or per internal node on MCM machines. Writing a valid
159 index to one of these files will cause the specificed cache
160 index to be disabled.
161
162 All AMD processors with L3 caches provide this functionality.
163 For details, see BKDGs at
164 http://developer.amd.com/documentation/guides/Pages/default.aspx
615b7300
AP		 165
166
167What: /sys/devices/system/cpu/cpufreq/boost
168Date: August 2012
169Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
170Description: Processor frequency boosting control
171
172 This switch controls the boost setting for the whole system.
173 Boosting allows the CPU and the firmware to run at a frequency
174 beyound it's nominal limit.
175 More details can be found in Documentation/cpu-freq/boost.txt
c4fd675f
ZY		 176
177
178What: /sys/devices/system/cpu/cpu#/crash_notes
179 /sys/devices/system/cpu/cpu#/crash_notes_size
180Date: April 2013
181Contact: kexec@lists.infradead.org
182Description: address and size of the percpu note.
183
184 crash_notes: the physical address of the memory that holds the
185 note of cpu#.
186
187 crash_notes_size: size of the note of cpu#.
Linux 6.x block layer and io_uring tree(s)