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Message-ID: <20091022034530.13399.65380.stgit@bob.kio>
Date: Wed, 21 Oct 2009 21:45:31 -0600
From: Alex Chiang <achiang@...com>
To: randy.dunlap@...cle.com, greg@...ah.com
Cc: akpm@...ux-foundation.org, Mike Travis <travis@....com>,
linux-kernel@...r.kernel.org,
Rusty Russell <rusty@...tcorp.com.au>, rientjes@...gle.com
Subject: [PATCH 4/7] 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@....com>
Cc: Rusty Russell <rusty@...tcorp.com.au>
Signed-off-by: Alex Chiang <achiang@...com>
---
Documentation/ABI/testing/sysfs-devices-system-cpu | 39 +++++++++++++++++
Documentation/cputopology.txt | 47 +++++++++++++-------
2 files changed, 69 insertions(+), 17 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 871acdb..2ade5c0 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -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@...r.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
diff --git a/Documentation/cputopology.txt b/Documentation/cputopology.txt
index b41f3e5..f1c5c4b 100644
--- a/Documentation/cputopology.txt
+++ b/Documentation/cputopology.txt
@@ -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.
--
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