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/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#/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: linux-pm@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#/cpufreq/freqdomain_cpus Date: June 2013 Contact: linux-pm@vger.kernel.org Description: Discover CPUs in the same CPU frequency coordination domain freqdomain_cpus is the list of CPUs (online+offline) that share the same clock/freq domain (possibly at the hardware level). That information may be hidden from the cpufreq core and the value of related_cpus may be different from freqdomain_cpus. This attribute is useful for user space DVFS controllers to get better power/performance results for platforms using acpi-cpufreq. This file is only present if the acpi-cpufreq driver is in use. What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1} Date: August 2008 KernelVersion: 2.6.27 Contact: Linux kernel mailing list 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/cpufreq/boost Date: August 2012 Contact: Linux kernel mailing list Description: Processor frequency boosting control This switch controls the boost setting for the whole system. Boosting allows the CPU and the firmware to run at a frequency beyound it's nominal limit. More details can be found in Documentation/cpu-freq/boost.txt What: /sys/devices/system/cpu/cpu#/crash_notes /sys/devices/system/cpu/cpu#/crash_notes_size Date: April 2013 Contact: kexec@lists.infradead.org Description: address and size of the percpu note. crash_notes: the physical address of the memory that holds the note of cpu#. crash_notes_size: size of the note of cpu#. What: /sys/devices/system/cpu/intel_pstate/max_perf_pct /sys/devices/system/cpu/intel_pstate/min_perf_pct /sys/devices/system/cpu/intel_pstate/no_turbo Date: February 2013 Contact: linux-pm@vger.kernel.org Description: Parameters for the Intel P-state driver Logic for selecting the current P-state in Intel Sandybridge+ processors. The three knobs control limits for the P-state that will be requested by the driver. max_perf_pct: limits the maximum P state that will be requested by the driver stated as a percentage of the available performance. min_perf_pct: limits the minimum P state that will be requested by the driver stated as a percentage of the available performance. no_turbo: limits the driver to selecting P states below the turbo frequency range. More details can be found in Documentation/cpu-freq/intel-pstate.txt What: /sys/devices/system/cpu/cpu*/cache/index*/ Date: July 2014(documented, existed before August 2008) Contact: Sudeep Holla Linux kernel mailing list Description: Parameters for the CPU cache attributes allocation_policy: - WriteAllocate: allocate a memory location to a cache line on a cache miss because of a write - ReadAllocate: allocate a memory location to a cache line on a cache miss because of a read - ReadWriteAllocate: both writeallocate and readallocate attributes: LEGACY used only on IA64 and is same as write_policy coherency_line_size: the minimum amount of data in bytes that gets transferred from memory to cache level: the cache hierarcy in the multi-level cache configuration number_of_sets: total number of sets in the cache, a set is a collection of cache lines with the same cache index physical_line_partition: number of physical cache line per cache tag shared_cpu_list: the list of logical cpus sharing the cache shared_cpu_map: logical cpu mask containing the list of cpus sharing the cache size: the total cache size in kB type: - Instruction: cache that only holds instructions - Data: cache that only caches data - Unified: cache that holds both data and instructions ways_of_associativity: degree of freedom in placing a particular block of memory in the cache write_policy: - WriteThrough: data is written to both the cache line and to the block in the lower-level memory - WriteBack: data is written only to the cache line and the modified cache line is written to main memory only when it is replaced