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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. 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 What: /sys/devices/system/cpu/cpu*/cache/index*/cache_disable_X
Date: August 2008 Date: August 2008
KernelVersion: 2.6.27 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. to /proc/cpuinfo.
1) /sys/devices/system/cpu/cpuX/topology/physical_package_id: 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: 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: 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: 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, To implement it in an architecture-neutral way, a new source file,
drivers/base/topology.c, is to export the 4 attributes. 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 3) thread_siblings: just the given CPU
4) core_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 /sys/devices/system/cpu and includes these files. The internal
source for the output is in brackets ("[]"). 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] [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 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] 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] 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] system. [cpu_present_mask]
The format for the above output is compatible with cpulist_parse() The format for the above output is compatible with cpulist_parse()
[see <linux/cpumask.h>]. Some examples follow. [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 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. brought online as they are both present and possible.
kernel_max: 31 kernel_max: 31
@ -67,8 +80,8 @@ brought online as they are both present and possible.
present: 0-31 present: 0-31
In this example, the NR_CPUS config option is 128, but the kernel was 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 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 was manually taken offline (and is the only CPU that can be brought
online.) online.)
kernel_max: 127 kernel_max: 127
@ -78,4 +91,4 @@ online.)
present: 0-3 present: 0-3
See cpu-hotplug.txt for the possible_cpus=NUM kernel start parameter 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.