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/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
  17 Date:           December 2008
  18 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
  19 Description:    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
  40 What:           /sys/devices/system/cpu/probe
  41                 /sys/devices/system/cpu/release
  42 Date:           November 2009
  43 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
  44 Description:    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
  56 What:           /sys/devices/system/cpu/cpu#/node
  57 Date:           October 2009
  58 Contact:        Linux memory management mailing list <linux-mm@kvack.org>
  59 Description:    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
  70 What:           /sys/devices/system/cpu/cpu#/node
  71 Date:           October 2009
  72 Contact:        Linux memory management mailing list <linux-mm@kvack.org>
  73 Description:    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
  84 What:           /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
  90 Date:           December 2008
  91 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
  92 Description:    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
 123 What:           /sys/devices/system/cpu/cpuidle/current_driver
 124                 /sys/devices/system/cpu/cpuidle/current_governer_ro
 125 Date:           September 2007
 126 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
 127 Description:    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
 143 What:           /sys/devices/system/cpu/cpu#/cpufreq/*
 144 Date:           pre-git history
 145 Contact:        cpufreq@vger.kernel.org
 146 Description:    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
 161 What:           /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
 162 Date:           August 2008
 163 KernelVersion:  2.6.27
 164 Contact:        discuss@x86-64.org
 165 Description:    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
 179
 180
 181 What:           /sys/devices/system/cpu/cpufreq/boost
 182 Date:           August 2012
 183 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
 184 Description:    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