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+What: /sys/devices/system/cpu/
+Date: pre-git history
+Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
+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 <linux-kernel@vger.kernel.org>
+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 <linux-kernel@vger.kernel.org>
+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 <linux-mm@kvack.org>
+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 <linux-kernel@vger.kernel.org>
+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
+ /sys/devices/system/cpu/cpuidle/available_governors
+ /sys/devices/system/cpu/cpuidle/current_governor
+Date: September 2007
+Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
+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: (RO) displays current idle mechanism
+
+ current_governor_ro: (RO) displays current idle policy
+
+ With the cpuidle_sysfs_switch boot option enabled (meant for
+ developer testing), the following three attributes are visible
+ instead:
+
+ current_driver: same as described above
+
+ available_governors: (RO) displays a space separated list of
+ available governors
+
+ current_governor: (RW) displays current idle policy. Users can
+ switch the governor at runtime by writing to this file.
+
+ See files in Documentation/cpuidle/ for more information.
+
+
+What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/name
+ /sys/devices/system/cpu/cpuX/cpuidle/stateN/latency
+ /sys/devices/system/cpu/cpuX/cpuidle/stateN/power
+ /sys/devices/system/cpu/cpuX/cpuidle/stateN/time
+ /sys/devices/system/cpu/cpuX/cpuidle/stateN/usage
+Date: September 2007
+KernelVersion: v2.6.24
+Contact: Linux power management list <linux-pm@vger.kernel.org>
+Description:
+ The directory /sys/devices/system/cpu/cpuX/cpuidle contains per
+ logical CPU specific cpuidle information for each online cpu X.
+ The processor idle states which are available for use have the
+ following attributes:
+
+ name: (RO) Name of the idle state (string).
+
+ latency: (RO) The latency to exit out of this idle state (in
+ microseconds).
+
+ power: (RO) The power consumed while in this idle state (in
+ milliwatts).
+
+ time: (RO) The total time spent in this idle state (in microseconds).
+
+ usage: (RO) Number of times this state was entered (a count).
+
+
+What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/desc
+Date: February 2008
+KernelVersion: v2.6.25
+Contact: Linux power management list <linux-pm@vger.kernel.org>
+Description:
+ (RO) A small description about the idle state (string).
+
+
+What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/disable
+Date: March 2012
+KernelVersion: v3.10
+Contact: Linux power management list <linux-pm@vger.kernel.org>
+Description:
+ (RW) Option to disable this idle state (bool). The behavior and
+ the effect of the disable variable depends on the implementation
+ of a particular governor. In the ladder governor, for example,
+ it is not coherent, i.e. if one is disabling a light state, then
+ all deeper states are disabled as well, but the disable variable
+ does not reflect it. Likewise, if one enables a deep state but a
+ lighter state still is disabled, then this has no effect.
+
+
+What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/residency
+Date: March 2014
+KernelVersion: v3.15
+Contact: Linux power management list <linux-pm@vger.kernel.org>
+Description:
+ (RO) Display the target residency i.e. the minimum amount of
+ time (in microseconds) this cpu should spend in this idle state
+ to make the transition worth the effort.
+
+What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/s2idle/
+Date: March 2018
+KernelVersion: v4.17
+Contact: Linux power management list <linux-pm@vger.kernel.org>
+Description:
+ Idle state usage statistics related to suspend-to-idle.
+
+ This attribute group is only present for states that can be
+ used in suspend-to-idle with suspended timekeeping.
+
+What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/s2idle/time
+Date: March 2018
+KernelVersion: v4.17
+Contact: Linux power management list <linux-pm@vger.kernel.org>
+Description:
+ Total time spent by the CPU in suspend-to-idle (with scheduler
+ tick suspended) after requesting this state.
+
+What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/s2idle/usage
+Date: March 2018
+KernelVersion: v4.17
+Contact: Linux power management list <linux-pm@vger.kernel.org>
+Description:
+ Total number of times this state has been requested by the CPU
+ while entering suspend-to-idle.
+
+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.
+
+
+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 <linux-kernel@vger.kernel.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/cpufreq/boost
+Date: August 2012
+Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
+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/admin-guide/pm/cpufreq.rst
+
+
+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/admin-guide/pm/intel_pstate.rst
+
+What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below>
+Date: July 2014(documented, existed before August 2008)
+Contact: Sudeep Holla <sudeep.holla@arm.com>
+ Linux kernel mailing list <linux-kernel@vger.kernel.org>
+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 hierarchy 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
+
+
+What: /sys/devices/system/cpu/cpu*/cache/index*/id
+Date: September 2016
+Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
+Description: Cache id
+
+ The id provides a unique number for a specific instance of
+ a cache of a particular type. E.g. there may be a level
+ 3 unified cache on each socket in a server and we may
+ assign them ids 0, 1, 2, ...
+
+ Note that id value can be non-contiguous. E.g. level 1
+ caches typically exist per core, but there may not be a
+ power of two cores on a socket, so these caches may be
+ numbered 0, 1, 2, 3, 4, 5, 8, 9, 10, ...
+
+What: /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats
+ /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/turbo_stat
+ /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/sub_turbo_stat
+ /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/unthrottle
+ /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/powercap
+ /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overtemp
+ /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/supply_fault
+ /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overcurrent
+ /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/occ_reset
+Date: March 2016
+Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
+ Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
+Description: POWERNV CPUFreq driver's frequency throttle stats directory and
+ attributes
+
+ 'cpuX/cpufreq/throttle_stats' directory contains the CPU frequency
+ throttle stat attributes for the chip. The throttle stats of a cpu
+ is common across all the cpus belonging to a chip. Below are the
+ throttle attributes exported in the 'throttle_stats' directory:
+
+ - turbo_stat : This file gives the total number of times the max
+ frequency is throttled to lower frequency in turbo (at and above
+ nominal frequency) range of frequencies.
+
+ - sub_turbo_stat : This file gives the total number of times the
+ max frequency is throttled to lower frequency in sub-turbo(below
+ nominal frequency) range of frequencies.
+
+ - unthrottle : This file gives the total number of times the max
+ frequency is unthrottled after being throttled.
+
+ - powercap : This file gives the total number of times the max
+ frequency is throttled due to 'Power Capping'.
+
+ - overtemp : This file gives the total number of times the max
+ frequency is throttled due to 'CPU Over Temperature'.
+
+ - supply_fault : This file gives the total number of times the
+ max frequency is throttled due to 'Power Supply Failure'.
+
+ - overcurrent : This file gives the total number of times the
+ max frequency is throttled due to 'Overcurrent'.
+
+ - occ_reset : This file gives the total number of times the max
+ frequency is throttled due to 'OCC Reset'.
+
+ The sysfs attributes representing different throttle reasons like
+ powercap, overtemp, supply_fault, overcurrent and occ_reset map to
+ the reasons provided by OCC firmware for throttling the frequency.
+
+What: /sys/devices/system/cpu/cpufreq/policyX/throttle_stats
+ /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/turbo_stat
+ /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/sub_turbo_stat
+ /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/unthrottle
+ /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/powercap
+ /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overtemp
+ /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/supply_fault
+ /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overcurrent
+ /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/occ_reset
+Date: March 2016
+Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
+ Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
+Description: POWERNV CPUFreq driver's frequency throttle stats directory and
+ attributes
+
+ 'policyX/throttle_stats' directory and all the attributes are same as
+ the /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats directory and
+ attributes which give the frequency throttle information of the chip.
+
+What: /sys/devices/system/cpu/cpuX/regs/
+ /sys/devices/system/cpu/cpuX/regs/identification/
+ /sys/devices/system/cpu/cpuX/regs/identification/midr_el1
+ /sys/devices/system/cpu/cpuX/regs/identification/revidr_el1
+Date: June 2016
+Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
+Description: AArch64 CPU registers
+ 'identification' directory exposes the CPU ID registers for
+ identifying model and revision of the CPU.
+
+What: /sys/devices/system/cpu/cpu#/cpu_capacity
+Date: December 2016
+Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
+Description: information about CPUs heterogeneity.
+
+ cpu_capacity: capacity of cpu#.
+
+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
+ /sys/devices/system/cpu/vulnerabilities/spec_store_bypass
+ /sys/devices/system/cpu/vulnerabilities/l1tf
+Date: January 2018
+Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
+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
+
+ Details about the l1tf file can be found in
+ Documentation/admin-guide/l1tf.rst
+
+What: /sys/devices/system/cpu/smt
+ /sys/devices/system/cpu/smt/active
+ /sys/devices/system/cpu/smt/control
+Date: June 2018
+Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
+Description: Control Symetric Multi Threading (SMT)
+
+ active: Tells whether SMT is active (enabled and siblings online)
+
+ control: Read/write interface to control SMT. Possible
+ values:
+
+ "on" SMT is enabled
+ "off" SMT is disabled
+ "forceoff" SMT is force disabled. Cannot be changed.
+ "notsupported" SMT is not supported by the CPU
+
+ If control status is "forceoff" or "notsupported" writes
+ are rejected.