What: /sys/devices/system/cpu/ Date: pre-git history Contact: Linux kernel mailing list Description: A collection of both global and individual CPU attributes Individual CPU attributes are contained in subdirectories named by the kernel's logical CPU number, e.g.: /sys/devices/system/cpu/cpu#/ What: /sys/devices/system/cpu/sched_mc_power_savings /sys/devices/system/cpu/sched_smt_power_savings Date: June 2006 Contact: Linux kernel mailing list Description: Discover and adjust the kernel's multi-core scheduler support. Possible values are: 0 - No power saving load balance (default value) 1 - Fill one thread/core/package first for long running threads 2 - Also bias task wakeups to semi-idle cpu package for power savings sched_mc_power_savings is dependent upon SCHED_MC, which is itself architecture dependent. sched_smt_power_savings is dependent upon SCHED_SMT, which is itself architecture dependent. The two files are independent of each other. It is possible that one file may be present without the other. Introduced by git commit 5c45bf27. What: /sys/devices/system/cpu/kernel_max /sys/devices/system/cpu/offline /sys/devices/system/cpu/online /sys/devices/system/cpu/possible /sys/devices/system/cpu/present Date: December 2008 Contact: Linux kernel mailing list Description: CPU topology files that describe kernel limits related to hotplug. Briefly: kernel_max: the maximum cpu index allowed by the kernel configuration. offline: cpus that are not online because they have been HOTPLUGGED off or exceed the limit of cpus allowed by the kernel configuration (kernel_max above). online: cpus that are online and being scheduled. possible: cpus that have been allocated resources and can be brought online if they are present. present: cpus that have been identified as being present in the system. See Documentation/cputopology.txt for more information. What: /sys/devices/system/cpu/probe /sys/devices/system/cpu/release Date: November 2009 Contact: Linux kernel mailing list Description: Dynamic addition and removal of CPU's. This is not hotplug removal, this is meant complete removal/addition of the CPU from the system. probe: writes to this file will dynamically add a CPU to the system. Information written to the file to add CPU's is architecture specific. release: writes to this file dynamically remove a CPU from the system. Information writtento the file to remove CPU's is architecture specific. What: /sys/devices/system/cpu/cpu#/node Date: October 2009 Contact: Linux memory management mailing list Description: Discover NUMA node a CPU belongs to When CONFIG_NUMA is enabled, a symbolic link that points to the corresponding NUMA node directory. For example, the following symlink is created for cpu42 in NUMA node 2: /sys/devices/system/cpu/cpu42/node2 -> ../../node/node2 What: /sys/devices/system/cpu/cpu#/node Date: October 2009 Contact: Linux memory management mailing list Description: Discover NUMA node a CPU belongs to When CONFIG_NUMA is enabled, a symbolic link that points to the corresponding NUMA node directory. For example, the following symlink is created for cpu42 in NUMA node 2: /sys/devices/system/cpu/cpu42/node2 -> ../../node/node2 What: /sys/devices/system/cpu/cpu#/topology/core_id /sys/devices/system/cpu/cpu#/topology/core_siblings /sys/devices/system/cpu/cpu#/topology/core_siblings_list /sys/devices/system/cpu/cpu#/topology/physical_package_id /sys/devices/system/cpu/cpu#/topology/thread_siblings /sys/devices/system/cpu/cpu#/topology/thread_siblings_list Date: December 2008 Contact: Linux kernel mailing list Description: CPU topology files that describe a logical CPU's relationship to other cores and threads in the same physical package. One cpu# directory is created per logical CPU in the system, e.g. /sys/devices/system/cpu/cpu42/. Briefly, the files above are: core_id: the CPU core ID of cpu#. Typically it is the hardware platform's identifier (rather than the kernel's). The actual value is architecture and platform dependent. core_siblings: internal kernel map of cpu#'s hardware threads within the same physical_package_id. core_siblings_list: human-readable list of the logical CPU numbers within the same physical_package_id as cpu#. physical_package_id: physical package id of cpu#. Typically corresponds to a physical socket number, but the actual value is architecture and platform dependent. thread_siblings: internel kernel map of cpu#'s hardware threads within the same core as cpu# thread_siblings_list: human-readable list of cpu#'s hardware threads within the same core as cpu# See Documentation/cputopology.txt for more information. What: /sys/devices/system/cpu/cpuidle/current_driver /sys/devices/system/cpu/cpuidle/current_governer_ro Date: September 2007 Contact: Linux kernel mailing list Description: Discover cpuidle policy and mechanism Various CPUs today support multiple idle levels that are differentiated by varying exit latencies and power consumption during idle. Idle policy (governor) is differentiated from idle mechanism (driver) current_driver: displays current idle mechanism current_governor_ro: displays current idle policy See files in Documentation/cpuidle/ for more information. What: /sys/devices/system/cpu/cpu#/cpufreq/* Date: pre-git history Contact: cpufreq@vger.kernel.org Description: Discover and change clock speed of CPUs Clock scaling allows you to change the clock speed of the CPUs on the fly. This is a nice method to save battery power, because the lower the clock speed, the less power the CPU consumes. There are many knobs to tweak in this directory. See files in Documentation/cpu-freq/ for more information. In particular, read Documentation/cpu-freq/user-guide.txt to learn how to control the knobs. What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1} Date: August 2008 KernelVersion: 2.6.27 Contact: discuss@x86-64.org Description: Disable L3 cache indices These files exist in every CPU's cache/index3 directory. Each cache_disable_{0,1} file corresponds to one disable slot which can be used to disable a cache index. Reading from these files on a processor with this functionality will return the currently disabled index for that node. There is one L3 structure per node, or per internal node on MCM machines. Writing a valid index to one of these files will cause the specificed cache index to be disabled. All AMD processors with L3 caches provide this functionality. For details, see BKDGs at http://developer.amd.com/documentation/guides/Pages/default.aspx What: /sys/devices/system/cpu/vulnerabilities /sys/devices/system/cpu/vulnerabilities/meltdown /sys/devices/system/cpu/vulnerabilities/spectre_v1 /sys/devices/system/cpu/vulnerabilities/spectre_v2 Date: January 2018 Contact: Linux kernel mailing list Description: Information about CPU vulnerabilities The files are named after the code names of CPU vulnerabilities. The output of those files reflects the state of the CPUs in the system. Possible output values: "Not affected" CPU is not affected by the vulnerability "Vulnerable" CPU is affected and no mitigation in effect "Mitigation: $M" CPU is affected and mitigation $M is in effect