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Commit 54a53694 authored by Bartosz Golaszewski's avatar Bartosz Golaszewski Committed by Ingo Molnar
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Documentation: Update cputopology.txt 



The documentation on cpu topology seems to be a bit out-of-date.
It doesn't mention the **_siblings_list attributes and uses old
names for topology_**_cpumask() macros.

Add information on missing attributes plus some additional
clarifications.

Signed-off-by: default avatarBartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Benoit Cousson <bcousson@baylibre.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Jean Delvare <jdelvare@suse.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Drokin <oleg.drokin@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Link: http://lkml.kernel.org/r/1432645896-12588-3-git-send-email-bgolaszewski@baylibre.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 06931e62

Documentation/cputopology.txt

+26 −9
Original line number Diff line number Diff line 


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

to /proc/cpuinfo.

to /proc/cpuinfo output of some architectures:



1) /sys/devices/system/cpu/cpuX/topology/physical_package_id:
@@ -23,20 +23,35 @@ to /proc/cpuinfo. 
4) /sys/devices/system/cpu/cpuX/topology/thread_siblings:



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

	core as cpuX

	core as cpuX.



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

5) /sys/devices/system/cpu/cpuX/topology/thread_siblings_list:



	human-readable list of cpuX's hardware threads within the same

	core as cpuX.



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



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

	physical_package_id.



6) /sys/devices/system/cpu/cpuX/topology/book_siblings:

7) /sys/devices/system/cpu/cpuX/topology/core_siblings_list:



	human-readable list of cpuX's hardware threads within the same

	physical_package_id.



8) /sys/devices/system/cpu/cpuX/topology/book_siblings:



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

	book_id.



9) /sys/devices/system/cpu/cpuX/topology/book_siblings_list:



	human-readable list of cpuX's hardware threads within the same

	book_id.



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

drivers/base/topology.c, is to export the 4 or 6 attributes. The two book

drivers/base/topology.c, is to export the 6 or 9 attributes. The three book

related sysfs files will only be created if CONFIG_SCHED_BOOK is selected.



For an architecture to support this feature, it must define some of
@@ -48,16 +63,18 @@ these macros in include/asm-XXX/topology.h: 
#define topology_core_cpumask(cpu)

#define topology_book_cpumask(cpu)



The type of **_id is int.

The type of siblings is (const) struct cpumask *.

The type of **_id macros is int.

The type of **_cpumask macros is (const) struct cpumask *. The latter

correspond with appropriate **_siblings sysfs attributes (except for

topology_sibling_cpumask() which corresponds with thread_siblings).



To be consistent on all architectures, include/linux/topology.h

provides default definitions for any of the above macros that are

not defined by include/asm-XXX/topology.h:

1) physical_package_id: -1

2) core_id: 0

3) thread_siblings: just the given CPU

4) core_siblings: just the given CPU

3) sibling_cpumask: just the given CPU

4) core_cpumask: just the given CPU



For architectures that don't support books (CONFIG_SCHED_BOOK) there are no

default definitions for topology_book_id() and topology_book_cpumask().