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Date:   Mon, 22 Apr 2019 02:35:29 +0800
From:   Aubrey Li <>
        Aubrey Li <>,
        Andy Lutomirski <>
Subject: [PATCH v17 3/3] Documentation/filesystems/proc.txt: add arch_status file

Added /proc/<pid>/arch_status file, and added AVX512_elapsed_ms in
/proc/<pid>/arch_status. Report it in Documentation/filesystems/proc.txt

Signed-off-by: Aubrey Li <>
Cc: Thomas Gleixner <>
Cc: Peter Zijlstra <>
Cc: Andi Kleen <>
Cc: Tim Chen <>
Cc: Dave Hansen <>
Cc: Arjan van de Ven <>
Cc: Alexey Dobriyan <>
Cc: Andrew Morton <>
Cc: Andy Lutomirski <>
Cc: Linux API <>
 Documentation/filesystems/proc.txt | 37 ++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 66cad5c86171..cf5114a8fb13 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 +1949,42 @@ 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.
+ $ cat /proc/6753/arch_status
+ AVX512_elapsed_ms:      8
+ 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.
+  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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