linux-yocto/Documentation/ABI/testing/sysfs-devices-system-cpu

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 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: 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: 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/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/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