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

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Add brief descriptions for the following sysfs files:

	/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

The descriptions in Documentation/cputopology.txt weren't very
informative, so I attempted a better description based on code
reading and hopeful guessing.

Updated Documentation/cputopology.txt with the better descriptions and
fixed some style issues.

Cc: Mike Travis <travis@sgi.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Alex Chiang 2009-10-21 21:45:31 -06:00 committed by Greg Kroah-Hartman
parent d93fc863d2
commit 663fb2fc73
2 changed files with 69 additions and 17 deletions
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39
Documentation/ABI/testing/sysfs-devices-system-cpu
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@ -38,6 +38,45 @@ Description: CPU topology files that describe kernel limits related to
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

47
Documentation/cputopology.txt
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@ -1,15 +1,28 @@
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.
@ -32,32 +45,32 @@ not defined by include/asm-XXX/topology.h:
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
@ -67,8 +80,8 @@ brought online as they are both present and possible.
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
@ -78,4 +91,4 @@ online.)
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.