Documentation: update broken web addresses.
[linux-2.6.git] / Documentation / ABI / testing / sysfs-devices-system-cpu
1 What:           /sys/devices/system/cpu/
2 Date:           pre-git history
3 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
4 Description:
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
12 What:           /sys/devices/system/cpu/sched_mc_power_savings
13                 /sys/devices/system/cpu/sched_smt_power_savings
14 Date:           June 2006
15 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
16 Description:    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
37 What:           /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
42 Date:           December 2008
43 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
44 Description:    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
65 What:           /sys/devices/system/cpu/probe
66                 /sys/devices/system/cpu/release
67 Date:           November 2009
68 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
69 Description:    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
81 What:           /sys/devices/system/cpu/cpu#/node
82 Date:           October 2009
83 Contact:        Linux memory management mailing list <linux-mm@kvack.org>
84 Description:    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
95 What:           /sys/devices/system/cpu/cpu#/node
96 Date:           October 2009
97 Contact:        Linux memory management mailing list <linux-mm@kvack.org>
98 Description:    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
109 What:           /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
115 Date:           December 2008
116 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
117 Description:    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
148 What:           /sys/devices/system/cpu/cpuidle/current_driver
149                 /sys/devices/system/cpu/cpuidle/current_governer_ro
150 Date:           September 2007
151 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
152 Description:    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
168 What:           /sys/devices/system/cpu/cpu#/cpufreq/*
169 Date:           pre-git history
170 Contact:        cpufreq@vger.kernel.org
171 Description:    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
186 What:      /sys/devices/system/cpu/cpu*/cache/index*/cache_disable_X
187 Date:      August 2008
188 KernelVersion:  2.6.27
189 Contact:        mark.langsdorf@amd.com
190 Description:    These files exist in every cpu's cache index directories.
191                 There are currently 2 cache_disable_# files in each
192                 directory.  Reading from these files on a supported
193                 processor will return that cache disable index value
194                 for that processor and node.  Writing to one of these
195                 files will cause the specificed cache index to be disabled.
196
197                 Currently, only AMD Family 10h Processors support cache index
198                 disable, and only for their L3 caches.  See the BIOS and
199                 Kernel Developer's Guide at
200                 http://support.amd.com/us/Embedded_TechDocs/31116-Public-GH-BKDG_3-28_5-28-09.pdf       
201                 for formatting information and other details on the
202                 cache index disable.
203 Users:    joachim.deguara@amd.com