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authorLinus Torvalds <torvalds@linux-foundation.org>2019-07-08 17:28:57 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-07-08 17:28:57 -0700
commit3431a940bb6c3969240d91314d654ebac7e12b09 (patch)
tree8d75363fe5bc959bf03d72bc1c00275fb759f153 /Documentation
parent5b7a2095232d026d4537c4be54040c0f10525b5b (diff)
parent711486fd18596315d42cebaac3dba8c408f60a3d (diff)
downloadlinux-3431a940bb6c3969240d91314d654ebac7e12b09.tar.bz2
Merge branch 'x86-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 AVX512 status update from Ingo Molnar: "This adds a new ABI that the main scheduler probably doesn't want to deal with but HPC job schedulers might want to use: the AVX512_elapsed_ms field in the new /proc/<pid>/arch_status task status file, which allows the user-space job scheduler to cluster such tasks, to avoid turbo frequency drops" * 'x86-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: Documentation/filesystems/proc.txt: Add arch_status file x86/process: Add AVX-512 usage elapsed time to /proc/pid/arch_status proc: Add /proc/<pid>/arch_status
Diffstat (limited to 'Documentation')
-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