Documentation: ABI: /sys/devices/system/cpu/cpu#/ topology files
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>
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Greg Kroah-Hartman
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@ -38,6 +38,45 @@ Description: CPU topology files that describe kernel limits related to
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See Documentation/cputopology.txt for more information.
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What: /sys/devices/system/cpu/cpu#/topology/core_id
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/sys/devices/system/cpu/cpu#/topology/core_siblings
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/sys/devices/system/cpu/cpu#/topology/core_siblings_list
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/sys/devices/system/cpu/cpu#/topology/physical_package_id
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/sys/devices/system/cpu/cpu#/topology/thread_siblings
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/sys/devices/system/cpu/cpu#/topology/thread_siblings_list
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Date: December 2008
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Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description: CPU topology files that describe a logical CPU's relationship
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to other cores and threads in the same physical package.
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One cpu# directory is created per logical CPU in the system,
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e.g. /sys/devices/system/cpu/cpu42/.
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Briefly, the files above are:
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core_id: the CPU core ID of cpu#. Typically it is the
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hardware platform's identifier (rather than the kernel's).
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The actual value is architecture and platform dependent.
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core_siblings: internal kernel map of cpu#'s hardware threads
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within the same physical_package_id.
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core_siblings_list: human-readable list of the logical CPU
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numbers within the same physical_package_id as cpu#.
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physical_package_id: physical package id of cpu#. Typically
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corresponds to a physical socket number, but the actual value
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is architecture and platform dependent.
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thread_siblings: internel kernel map of cpu#'s hardware
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threads within the same core as cpu#
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thread_siblings_list: human-readable list of cpu#'s hardware
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threads within the same core as cpu#
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See Documentation/cputopology.txt for more information.
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What: /sys/devices/system/cpu/cpu*/cache/index*/cache_disable_X
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Date: August 2008
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KernelVersion: 2.6.27
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@ -1,15 +1,28 @@
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Export cpu topology info via sysfs. Items (attributes) are similar
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Export CPU topology info via sysfs. Items (attributes) are similar
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to /proc/cpuinfo.
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1) /sys/devices/system/cpu/cpuX/topology/physical_package_id:
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represent the physical package id of cpu X;
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physical package id of cpuX. Typically corresponds to a physical
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socket number, but the actual value is architecture and platform
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dependent.
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2) /sys/devices/system/cpu/cpuX/topology/core_id:
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represent the cpu core id to cpu X;
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the CPU core ID of cpuX. Typically it is the hardware platform's
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identifier (rather than the kernel's). The actual value is
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architecture and platform dependent.
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3) /sys/devices/system/cpu/cpuX/topology/thread_siblings:
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represent the thread siblings to cpu X in the same core;
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internel kernel map of cpuX's hardware threads within the same
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core as cpuX
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4) /sys/devices/system/cpu/cpuX/topology/core_siblings:
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represent the thread siblings to cpu X in the same physical package;
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internal kernel map of cpuX's hardware threads within the same
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physical_package_id.
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To implement it in an architecture-neutral way, a new source file,
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drivers/base/topology.c, is to export the 4 attributes.
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@ -32,32 +45,32 @@ not defined by include/asm-XXX/topology.h:
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3) thread_siblings: just the given CPU
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4) core_siblings: just the given CPU
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Additionally, cpu topology information is provided under
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Additionally, CPU topology information is provided under
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/sys/devices/system/cpu and includes these files. The internal
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source for the output is in brackets ("[]").
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kernel_max: the maximum cpu index allowed by the kernel configuration.
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kernel_max: the maximum CPU index allowed by the kernel configuration.
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[NR_CPUS-1]
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offline: cpus that are not online because they have been
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offline: CPUs that are not online because they have been
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HOTPLUGGED off (see cpu-hotplug.txt) or exceed the limit
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of cpus allowed by the kernel configuration (kernel_max
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of CPUs allowed by the kernel configuration (kernel_max
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above). [~cpu_online_mask + cpus >= NR_CPUS]
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online: cpus that are online and being scheduled [cpu_online_mask]
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online: CPUs that are online and being scheduled [cpu_online_mask]
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possible: cpus that have been allocated resources and can be
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possible: CPUs that have been allocated resources and can be
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brought online if they are present. [cpu_possible_mask]
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present: cpus that have been identified as being present in the
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present: CPUs that have been identified as being present in the
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system. [cpu_present_mask]
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The format for the above output is compatible with cpulist_parse()
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[see <linux/cpumask.h>]. Some examples follow.
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In this example, there are 64 cpus in the system but cpus 32-63 exceed
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In this example, there are 64 CPUs in the system but cpus 32-63 exceed
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the kernel max which is limited to 0..31 by the NR_CPUS config option
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being 32. Note also that cpus 2 and 4-31 are not online but could be
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being 32. Note also that CPUs 2 and 4-31 are not online but could be
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brought online as they are both present and possible.
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kernel_max: 31
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@ -67,8 +80,8 @@ brought online as they are both present and possible.
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present: 0-31
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In this example, the NR_CPUS config option is 128, but the kernel was
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started with possible_cpus=144. There are 4 cpus in the system and cpu2
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was manually taken offline (and is the only cpu that can be brought
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started with possible_cpus=144. There are 4 CPUs in the system and cpu2
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was manually taken offline (and is the only CPU that can be brought
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online.)
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kernel_max: 127
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@ -78,4 +91,4 @@ online.)
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present: 0-3
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See cpu-hotplug.txt for the possible_cpus=NUM kernel start parameter
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as well as more information on the various cpumask's.
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as well as more information on the various cpumasks.
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