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/index*/cache_disable_X 187Date: August 2008 188KernelVersion: 2.6.27 189Contact: mark.langsdorf@amd.com 190Description: 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. 203Users: joachim.deguara@amd.com 204