[mirror_ubuntu-bionic-kernel.git] / 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:	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#/cpufreq/freqdomain_cpus
Date:		June 2013
Contact:	cpufreq@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#.
Commit	Line	Data
2ceb3fb0 AC	1	What: /sys/devices/system/cpu/
	2	Date: pre-git history
	3	Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
	4	Description:
	5	A collection of both global and individual CPU attributes
	6
	7	Individual CPU attributes are contained in subdirectories
	8	named by the kernel's logical CPU number, e.g.:
	9
	10	/sys/devices/system/cpu/cpu#/
	11
d93fc863 AC	12	What: /sys/devices/system/cpu/kernel_max
	13	/sys/devices/system/cpu/offline
	14	/sys/devices/system/cpu/online
	15	/sys/devices/system/cpu/possible
	16	/sys/devices/system/cpu/present
	17	Date: December 2008
	18	Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
	19	Description: CPU topology files that describe kernel limits related to
	20	hotplug. Briefly:
	21
	22	kernel_max: the maximum cpu index allowed by the kernel
	23	configuration.
	24
	25	offline: cpus that are not online because they have been
	26	HOTPLUGGED off or exceed the limit of cpus allowed by the
	27	kernel configuration (kernel_max above).
	28
	29	online: cpus that are online and being scheduled.
	30
	31	possible: cpus that have been allocated resources and can be
	32	brought online if they are present.
	33
	34	present: cpus that have been identified as being present in
	35	the system.
	36
	37	See Documentation/cputopology.txt for more information.
	38
	39
12633e80 NF	40	What: /sys/devices/system/cpu/probe
	41	/sys/devices/system/cpu/release
	42	Date: November 2009
	43	Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
	44	Description: Dynamic addition and removal of CPU's. This is not hotplug
	45	removal, this is meant complete removal/addition of the CPU
	46	from the system.
	47
	48	probe: writes to this file will dynamically add a CPU to the
	49	system. Information written to the file to add CPU's is
	50	architecture specific.
	51
	52	release: writes to this file dynamically remove a CPU from
	53	the system. Information writtento the file to remove CPU's
	54	is architecture specific.
657348a0	55
cba5dd7f AC	56	What: /sys/devices/system/cpu/cpu#/node
	57	Date: October 2009
	58	Contact: Linux memory management mailing list <linux-mm@kvack.org>
	59	Description: Discover NUMA node a CPU belongs to
	60
	61	When CONFIG_NUMA is enabled, a symbolic link that points
	62	to the corresponding NUMA node directory.
	63
	64	For example, the following symlink is created for cpu42
	65	in NUMA node 2:
	66
	67	/sys/devices/system/cpu/cpu42/node2 -> ../../node/node2
	68
	69
663fb2fc AC	70	What: /sys/devices/system/cpu/cpu#/topology/core_id
	71	/sys/devices/system/cpu/cpu#/topology/core_siblings
	72	/sys/devices/system/cpu/cpu#/topology/core_siblings_list
	73	/sys/devices/system/cpu/cpu#/topology/physical_package_id
	74	/sys/devices/system/cpu/cpu#/topology/thread_siblings
	75	/sys/devices/system/cpu/cpu#/topology/thread_siblings_list
	76	Date: December 2008
	77	Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
	78	Description: CPU topology files that describe a logical CPU's relationship
	79	to other cores and threads in the same physical package.
	80
	81	One cpu# directory is created per logical CPU in the system,
	82	e.g. /sys/devices/system/cpu/cpu42/.
	83
	84	Briefly, the files above are:
	85
	86	core_id: the CPU core ID of cpu#. Typically it is the
	87	hardware platform's identifier (rather than the kernel's).
	88	The actual value is architecture and platform dependent.
	89
	90	core_siblings: internal kernel map of cpu#'s hardware threads
	91	within the same physical_package_id.
	92
	93	core_siblings_list: human-readable list of the logical CPU
	94	numbers within the same physical_package_id as cpu#.
	95
	96	physical_package_id: physical package id of cpu#. Typically
	97	corresponds to a physical socket number, but the actual value
	98	is architecture and platform dependent.
	99
	100	thread_siblings: internel kernel map of cpu#'s hardware
	101	threads within the same core as cpu#
	102
	103	thread_siblings_list: human-readable list of cpu#'s hardware
	104	threads within the same core as cpu#
	105
	106	See Documentation/cputopology.txt for more information.
	107
	108
c1fb5c47 AC	109	What: /sys/devices/system/cpu/cpuidle/current_driver
	110	/sys/devices/system/cpu/cpuidle/current_governer_ro
	111	Date: September 2007
	112	Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
	113	Description: Discover cpuidle policy and mechanism
	114
	115	Various CPUs today support multiple idle levels that are
	116	differentiated by varying exit latencies and power
	117	consumption during idle.
	118
	119	Idle policy (governor) is differentiated from idle mechanism
	120	(driver)
	121
	122	current_driver: displays current idle mechanism
	123
	124	current_governor_ro: displays current idle policy
	125
	126	See files in Documentation/cpuidle/ for more information.
	127
	128
0cda8b91 AC	129	What: /sys/devices/system/cpu/cpu#/cpufreq/*
	130	Date: pre-git history
	131	Contact: cpufreq@vger.kernel.org
	132	Description: Discover and change clock speed of CPUs
	133
	134	Clock scaling allows you to change the clock speed of the
	135	CPUs on the fly. This is a nice method to save battery
	136	power, because the lower the clock speed, the less power
	137	the CPU consumes.
	138
	139	There are many knobs to tweak in this directory.
	140
	141	See files in Documentation/cpu-freq/ for more information.
	142
	143	In particular, read Documentation/cpu-freq/user-guide.txt
	144	to learn how to control the knobs.
	145
	146
f4fd3797 LT	147	What: /sys/devices/system/cpu/cpu#/cpufreq/freqdomain_cpus
	148	Date: June 2013
	149	Contact: cpufreq@vger.kernel.org
	150	Description: Discover CPUs in the same CPU frequency coordination domain
	151
	152	freqdomain_cpus is the list of CPUs (online+offline) that share
	153	the same clock/freq domain (possibly at the hardware level).
	154	That information may be hidden from the cpufreq core and the
	155	value of related_cpus may be different from freqdomain_cpus. This
	156	attribute is useful for user space DVFS controllers to get better
	157	power/performance results for platforms using acpi-cpufreq.
	158
	159	This file is only present if the acpi-cpufreq driver is in use.
	160
	161
eecaaba5 BP	162	What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
eecaaba5 BP	163	Date: August 2008
2fad2d9b	164	KernelVersion: 2.6.27
eecaaba5 BP	165	Contact: discuss@x86-64.org
	166	Description: Disable L3 cache indices
	167
	168	These files exist in every CPU's cache/index3 directory. Each
	169	cache_disable_{0,1} file corresponds to one disable slot which
	170	can be used to disable a cache index. Reading from these files
	171	on a processor with this functionality will return the currently
	172	disabled index for that node. There is one L3 structure per
	173	node, or per internal node on MCM machines. Writing a valid
	174	index to one of these files will cause the specificed cache
	175	index to be disabled.
	176
	177	All AMD processors with L3 caches provide this functionality.
	178	For details, see BKDGs at
	179	http://developer.amd.com/documentation/guides/Pages/default.aspx
615b7300 AP	180
	181
	182	What: /sys/devices/system/cpu/cpufreq/boost
	183	Date: August 2012
	184	Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
	185	Description: Processor frequency boosting control
	186
	187	This switch controls the boost setting for the whole system.
	188	Boosting allows the CPU and the firmware to run at a frequency
	189	beyound it's nominal limit.
	190	More details can be found in Documentation/cpu-freq/boost.txt
c4fd675f ZY	191
	192
	193	What: /sys/devices/system/cpu/cpu#/crash_notes
	194	/sys/devices/system/cpu/cpu#/crash_notes_size
	195	Date: April 2013
	196	Contact: kexec@lists.infradead.org
	197	Description: address and size of the percpu note.
	198
	199	crash_notes: the physical address of the memory that holds the
	200	note of cpu#.
	201
	202	crash_notes_size: size of the note of cpu#.