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/cpu#/topology/core_id
  66                 /sys/devices/system/cpu/cpu#/topology/core_siblings
  67                 /sys/devices/system/cpu/cpu#/topology/core_siblings_list
  68                 /sys/devices/system/cpu/cpu#/topology/physical_package_id
  69                 /sys/devices/system/cpu/cpu#/topology/thread_siblings
  70                 /sys/devices/system/cpu/cpu#/topology/thread_siblings_list
  71 Date:           December 2008
  72 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
  73 Description:    CPU topology files that describe a logical CPU's relationship
  74                 to other cores and threads in the same physical package.
  75
  76                 One cpu# directory is created per logical CPU in the system,
  77                 e.g. /sys/devices/system/cpu/cpu42/.
  78
  79                 Briefly, the files above are:
  80
  81                 core_id: the CPU core ID of cpu#. Typically it is the
  82                 hardware platform's identifier (rather than the kernel's).
  83                 The actual value is architecture and platform dependent.
  84
  85                 core_siblings: internal kernel map of cpu#'s hardware threads
  86                 within the same physical_package_id.
  87
  88                 core_siblings_list: human-readable list of the logical CPU
  89                 numbers within the same physical_package_id as cpu#.
  90
  91                 physical_package_id: physical package id of cpu#. Typically
  92                 corresponds to a physical socket number, but the actual value
  93                 is architecture and platform dependent.
  94
  95                 thread_siblings: internel kernel map of cpu#'s hardware
  96                 threads within the same core as cpu#
  97
  98                 thread_siblings_list: human-readable list of cpu#'s hardware
  99                 threads within the same core as cpu#
 100
 101                 See Documentation/cputopology.txt for more information.
 102
 103
 104 What:           /sys/devices/system/cpu/cpuidle/current_driver
 105                 /sys/devices/system/cpu/cpuidle/current_governer_ro
 106 Date:           September 2007
 107 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
 108 Description:    Discover cpuidle policy and mechanism
 109
 110                 Various CPUs today support multiple idle levels that are
 111                 differentiated by varying exit latencies and power
 112                 consumption during idle.
 113
 114                 Idle policy (governor) is differentiated from idle mechanism
 115                 (driver)
 116
 117                 current_driver: displays current idle mechanism
 118
 119                 current_governor_ro: displays current idle policy
 120
 121                 See files in Documentation/cpuidle/ for more information.
 122
 123
 124 What:      /sys/devices/system/cpu/cpu*/cache/index*/cache_disable_X
 125 Date:      August 2008
 126 KernelVersion:  2.6.27
 127 Contact:        mark.langsdorf@amd.com
 128 Description:    These files exist in every cpu's cache index directories.
 129                 There are currently 2 cache_disable_# files in each
 130                 directory.  Reading from these files on a supported
 131                 processor will return that cache disable index value
 132                 for that processor and node.  Writing to one of these
 133                 files will cause the specificed cache index to be disabled.
 134
 135                 Currently, only AMD Family 10h Processors support cache index
 136                 disable, and only for their L3 caches.  See the BIOS and
 137                 Kernel Developer's Guide at
 138                 http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/31116-Public-GH-BKDG_3.20_2-4-09.pdf
 139                 for formatting information and other details on the
 140                 cache index disable.
 141 Users:    joachim.deguara@amd.com