Commit 3a1c779f authored by Len Brown's avatar Len Brown Committed by Ingo Molnar
Browse files

topology: Simplify cputopology.txt formatting and wording 



Syntax only, no functional or semantic change.

Signed-off-by: default avatarLen Brown <len.brown@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-doc@vger.kernel.org
Link: http://lkml.kernel.org/r/1ca56f8ea922a67f0017bd645912ea02a65a85ec.1551160674.git.len.brown@intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ef7c7727

Documentation/cputopology.txt

+23 −23
Original line number Diff line number Diff line
@@ -3,79 +3,79 @@ How CPU topology info is exported via sysfs 
===========================================



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

to /proc/cpuinfo output of some architectures:

to /proc/cpuinfo output of some architectures.  They reside in

/sys/devices/system/cpu/cpuX/topology/:



1) /sys/devices/system/cpu/cpuX/topology/physical_package_id:

physical_package_id:



	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:

core_id:



	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/book_id:

book_id:



	the book ID of cpuX. Typically it is the hardware platform's

	identifier (rather than the kernel's).	The actual value is

	architecture and platform dependent.



4) /sys/devices/system/cpu/cpuX/topology/drawer_id:

drawer_id:



	the drawer ID of cpuX. Typically it is the hardware platform's

	identifier (rather than the kernel's).	The actual value is

	architecture and platform dependent.



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

thread_siblings:



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

	core as cpuX.



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

thread_siblings_list:



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

	core as cpuX.



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

core_siblings:



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

	physical_package_id.



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

core_siblings_list:



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

	physical_package_id.



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

book_siblings:



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

	book_id.



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

book_siblings_list:



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

	book_id.



11) /sys/devices/system/cpu/cpuX/topology/drawer_siblings:

drawer_siblings:



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

	drawer_id.



12) /sys/devices/system/cpu/cpuX/topology/drawer_siblings_list:

drawer_siblings_list:



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

	drawer_id.



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

drivers/base/topology.c, is to export the 6 to 12 attributes. The book

and drawer related sysfs files will only be created if CONFIG_SCHED_BOOK

and CONFIG_SCHED_DRAWER are selected.

Architecture-neutral, drivers/base/topology.c, exports these attributes.

However, the book and drawer related sysfs files will only be created if

CONFIG_SCHED_BOOK and CONFIG_SCHED_DRAWER are selected, respectively.



CONFIG_SCHED_BOOK and CONFIG_DRAWER are currently only used on s390, where

they reflect the cpu and cache hierarchy.

CONFIG_SCHED_BOOK and CONFIG_SCHED_DRAWER are currently only used on s390,

where they reflect the cpu and cache hierarchy.



For an architecture to support this feature, it must define some of

these macros in include/asm-XXX/topology.h::
@@ -98,10 +98,10 @@ 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) sibling_cpumask: just the given CPU

4) core_cpumask: just the given CPU

1) topology_physical_package_id: -1

2) topology_core_id: 0

3) topology_sibling_cpumask: just the given CPU

4) topology_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().

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