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/sched_mc_power_savings
		/sys/devices/system/cpu/sched_smt_power_savings
Date:		June 2006
Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
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 <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#/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:	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/index*/cache_disable_X
Date:      August 2008
KernelVersion:	2.6.27
Contact:	mark.langsdorf@amd.com
Description:	These files exist in every cpu's cache index directories.
		There are currently 2 cache_disable_# files in each
		directory.  Reading from these files on a supported
		processor will return that cache disable index value
		for that processor and node.  Writing to one of these
		files will cause the specificed cache index to be disabled.

		Currently, only AMD Family 10h Processors support cache index
		disable, and only for their L3 caches.  See the BIOS and
		Kernel Developer's Guide at
		http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/31116-Public-GH-BKDG_3.20_2-4-09.pdf
		for formatting information and other details on the
		cache index disable.
Users:    joachim.deguara@amd.com