Commit 711486fd authored by Aubrey Li's avatar Aubrey Li Committed by Thomas Gleixner
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Documentation/filesystems/proc.txt: Add arch_status file 



Add documentation for /proc/<pid>/arch_status file and the x86 specific
AVX512_elapsed_ms entry in it.

[ tglx: Massage changelog ]

Signed-off-by: default avatarAubrey Li <aubrey.li@linux.intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: akpm@linux-foundation.org
Cc: peterz@infradead.org
Cc: hpa@zytor.com
Cc: ak@linux.intel.com
Cc: tim.c.chen@linux.intel.com
Cc: dave.hansen@intel.com
Cc: arjan@linux.intel.com
Cc: adobriyan@gmail.com
Cc: aubrey.li@intel.com
Cc: linux-api@vger.kernel.org
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linux API <linux-api@vger.kernel.org>
Link: https://lkml.kernel.org/r/20190606012236.9391-3-aubrey.li@linux.intel.com
parent 0c608dad

Documentation/filesystems/proc.txt

+40 −0
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ Table of Contents 
  3.9   /proc/<pid>/map_files - Information about memory mapped files

  3.10  /proc/<pid>/timerslack_ns - Task timerslack value

  3.11	/proc/<pid>/patch_state - Livepatch patch operation state

  3.12	/proc/<pid>/arch_status - Task architecture specific information



  4	Configuring procfs

  4.1	Mount options
@@ -1948,6 +1949,45 @@ patched. If the patch is being enabled, then the task has already been 
patched.  If the patch is being disabled, then the task hasn't been

unpatched yet.



3.12 /proc/<pid>/arch_status - task architecture specific status

-------------------------------------------------------------------

When CONFIG_PROC_PID_ARCH_STATUS is enabled, this file displays the

architecture specific status of the task.



Example

-------

 $ cat /proc/6753/arch_status

 AVX512_elapsed_ms:      8



Description

-----------



x86 specific entries:

---------------------

 AVX512_elapsed_ms:

 ------------------

  If AVX512 is supported on the machine, this entry shows the milliseconds

  elapsed since the last time AVX512 usage was recorded. The recording

  happens on a best effort basis when a task is scheduled out. This means

  that the value depends on two factors:



    1) The time which the task spent on the CPU without being scheduled

       out. With CPU isolation and a single runnable task this can take

       several seconds.



    2) The time since the task was scheduled out last. Depending on the

       reason for being scheduled out (time slice exhausted, syscall ...)

       this can be arbitrary long time.



  As a consequence the value cannot be considered precise and authoritative

  information. The application which uses this information has to be aware

  of the overall scenario on the system in order to determine whether a

  task is a real AVX512 user or not. Precise information can be obtained

  with performance counters.



  A special value of '-1' indicates that no AVX512 usage was recorded, thus

  the task is unlikely an AVX512 user, but depends on the workload and the

  scheduling scenario, it also could be a false negative mentioned above.



------------------------------------------------------------------------------

Configuring procfs

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