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
  66 What:           /sys/devices/system/cpu/cpu#/node
  67 Date:           October 2009
  68 Contact:        Linux memory management mailing list <linux-mm@kvack.org>
  69 Description:    Discover NUMA node a CPU belongs to
  70
  71                 When CONFIG_NUMA is enabled, a symbolic link that points
  72                 to the corresponding NUMA node directory.
  73
  74                 For example, the following symlink is created for cpu42
  75                 in NUMA node 2:
  76
  77                 /sys/devices/system/cpu/cpu42/node2 -> ../../node/node2
  78
  79
  80 What:           /sys/devices/system/cpu/cpu#/topology/core_id
  81                 /sys/devices/system/cpu/cpu#/topology/core_siblings
  82                 /sys/devices/system/cpu/cpu#/topology/core_siblings_list
  83                 /sys/devices/system/cpu/cpu#/topology/physical_package_id
  84                 /sys/devices/system/cpu/cpu#/topology/thread_siblings
  85                 /sys/devices/system/cpu/cpu#/topology/thread_siblings_list
  86 Date:           December 2008
  87 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
  88 Description:    CPU topology files that describe a logical CPU's relationship
  89                 to other cores and threads in the same physical package.
  90
  91                 One cpu# directory is created per logical CPU in the system,
  92                 e.g. /sys/devices/system/cpu/cpu42/.
  93
  94                 Briefly, the files above are:
  95
  96                 core_id: the CPU core ID of cpu#. Typically it is the
  97                 hardware platform's identifier (rather than the kernel's).
  98                 The actual value is architecture and platform dependent.
  99
 100                 core_siblings: internal kernel map of cpu#'s hardware threads
 101                 within the same physical_package_id.
 102
 103                 core_siblings_list: human-readable list of the logical CPU
 104                 numbers within the same physical_package_id as cpu#.
 105
 106                 physical_package_id: physical package id of cpu#. Typically
 107                 corresponds to a physical socket number, but the actual value
 108                 is architecture and platform dependent.
 109
 110                 thread_siblings: internel kernel map of cpu#'s hardware
 111                 threads within the same core as cpu#
 112
 113                 thread_siblings_list: human-readable list of cpu#'s hardware
 114                 threads within the same core as cpu#
 115
 116                 See Documentation/cputopology.txt for more information.
 117
 118
 119 What:           /sys/devices/system/cpu/cpuidle/current_driver
 120                 /sys/devices/system/cpu/cpuidle/current_governer_ro
 121 Date:           September 2007
 122 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
 123 Description:    Discover cpuidle policy and mechanism
 124
 125                 Various CPUs today support multiple idle levels that are
 126                 differentiated by varying exit latencies and power
 127                 consumption during idle.
 128
 129                 Idle policy (governor) is differentiated from idle mechanism
 130                 (driver)
 131
 132                 current_driver: displays current idle mechanism
 133
 134                 current_governor_ro: displays current idle policy
 135
 136                 See files in Documentation/cpuidle/ for more information.
 137
 138
 139 What:           /sys/devices/system/cpu/cpu#/cpufreq/*
 140 Date:           pre-git history
 141 Contact:        cpufreq@vger.kernel.org
 142 Description:    Discover and change clock speed of CPUs
 143
 144                 Clock scaling allows you to change the clock speed of the
 145                 CPUs on the fly. This is a nice method to save battery
 146                 power, because the lower the clock speed, the less power
 147                 the CPU consumes.
 148
 149                 There are many knobs to tweak in this directory.
 150
 151                 See files in Documentation/cpu-freq/ for more information.
 152
 153                 In particular, read Documentation/cpu-freq/user-guide.txt
 154                 to learn how to control the knobs.
 155
 156
 157 What:      /sys/devices/system/cpu/cpu*/cache/index*/cache_disable_X
 158 Date:      August 2008
 159 KernelVersion:  2.6.27
 160 Contact:        mark.langsdorf@amd.com
 161 Description:    These files exist in every cpu's cache index directories.
 162                 There are currently 2 cache_disable_# files in each
 163                 directory.  Reading from these files on a supported
 164                 processor will return that cache disable index value
 165                 for that processor and node.  Writing to one of these
 166                 files will cause the specificed cache index to be disabled.
 167
 168                 Currently, only AMD Family 10h Processors support cache index
 169                 disable, and only for their L3 caches.  See the BIOS and
 170                 Kernel Developer's Guide at
 171                 http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/31116-Public-GH-BKDG_3.20_2-4-09.pdf
 172                 for formatting information and other details on the
 173                 cache index disable.
 174 Users:    joachim.deguara@amd.com