Documentation: ABI: /sys/devices/system/cpu/cpu#/ topology files

		See Documentation/cputopology.txt for more information.

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/cpu*/cache/index*/cache_disable_X

Date:      August 2008

KernelVersion:	2.6.27

Export cpu topology info via sysfs. Items (attributes) are similar

Export CPU topology info via sysfs. Items (attributes) are similar

to /proc/cpuinfo.

1) /sys/devices/system/cpu/cpuX/topology/physical_package_id:

represent the physical package id of  cpu X;

	physical package id of cpuX. Typically corresponds to a physical

	socket number, but the actual value is architecture and platform

	dependent.

2) /sys/devices/system/cpu/cpuX/topology/core_id:

represent the cpu core id to cpu X;

	the CPU core ID of cpuX. Typically it is the hardware platform's

	identifier (rather than the kernel's).  The actual value is

	architecture and platform dependent.

3) /sys/devices/system/cpu/cpuX/topology/thread_siblings:

represent the thread siblings to cpu X in the same core;

	internel kernel map of cpuX's hardware threads within the same

	core as cpuX

4) /sys/devices/system/cpu/cpuX/topology/core_siblings:

represent the thread siblings to cpu X in the same physical package;

	internal kernel map of cpuX's hardware threads within the same

	physical_package_id.

To implement it in an architecture-neutral way, a new source file,

drivers/base/topology.c, is to export the 4 attributes.

3) thread_siblings: just the given CPU

4) core_siblings: just the given CPU

Additionally, cpu topology information is provided under

Additionally, CPU topology information is provided under

/sys/devices/system/cpu and includes these files.  The internal

source for the output is in brackets ("[]").

    kernel_max: the maximum cpu index allowed by the kernel configuration.

    kernel_max: the maximum CPU index allowed by the kernel configuration.

		[NR_CPUS-1]

    offline:	cpus that are not online because they have been

    offline:	CPUs that are not online because they have been

		HOTPLUGGED off (see cpu-hotplug.txt) or exceed the limit

		of cpus allowed by the kernel configuration (kernel_max

		of CPUs allowed by the kernel configuration (kernel_max

		above). [~cpu_online_mask + cpus >= NR_CPUS]

    online:	cpus that are online and being scheduled [cpu_online_mask]

    online:	CPUs that are online and being scheduled [cpu_online_mask]

    possible:	cpus that have been allocated resources and can be

    possible:	CPUs that have been allocated resources and can be

		brought online if they are present. [cpu_possible_mask]

    present:	cpus that have been identified as being present in the

    present:	CPUs that have been identified as being present in the

		system. [cpu_present_mask]

The format for the above output is compatible with cpulist_parse()

[see <linux/cpumask.h>].  Some examples follow.

In this example, there are 64 cpus in the system but cpus 32-63 exceed

In this example, there are 64 CPUs in the system but cpus 32-63 exceed

the kernel max which is limited to 0..31 by the NR_CPUS config option

being 32.  Note also that cpus 2 and 4-31 are not online but could be

being 32.  Note also that CPUs 2 and 4-31 are not online but could be

brought online as they are both present and possible.

     kernel_max: 31

        present: 0-31

In this example, the NR_CPUS config option is 128, but the kernel was

started with possible_cpus=144.  There are 4 cpus in the system and cpu2

was manually taken offline (and is the only cpu that can be brought

started with possible_cpus=144.  There are 4 CPUs in the system and cpu2

was manually taken offline (and is the only CPU that can be brought

online.)

     kernel_max: 127

        present: 0-3

See cpu-hotplug.txt for the possible_cpus=NUM kernel start parameter

as well as more information on the various cpumask's.

as well as more information on the various cpumasks.