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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#/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
84What: /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
123What: /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
143What: /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
161What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
162Date: August 2008
163KernelVersion: 2.6.27
164Contact: discuss@x86-64.org
165Description: Disable L3 cache indices
166
167 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