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authorAubrey Li <aubrey.li@linux.intel.com>2019-06-06 09:22:36 +0800
committerThomas Gleixner <tglx@linutronix.de>2019-06-12 11:42:13 +0200
commit711486fd18596315d42cebaac3dba8c408f60a3d (patch)
treecc7f11f078930c1e8489ff1ed27a3c17addd2e0d /Documentation/filesystems/proc.txt
parent0c608dad2a771c0a11b6d12148d1a8b975e015d4 (diff)
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: Aubrey Li <aubrey.li@linux.intel.com> Signed-off-by: Thomas 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
Diffstat (limited to 'Documentation/filesystems/proc.txt')
-rw-r--r--Documentation/filesystems/proc.txt40
1 files changed, 40 insertions, 0 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 66cad5c86171..a226061fa109 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -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