The patch titled
Subject: sched/fair: use try_cmpxchg in task_numa_work
has been added to the -mm mm-nonmm-unstable branch. Its filename is
sched-fair-use-try_cmpxchg-in-task_numa_work.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/sched-fair-use-try_cmpxchg-in-task_numa_work.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Uros Bizjak <ubizjak@xxxxxxxxx>
Subject: sched/fair: use try_cmpxchg in task_numa_work
Date: Mon, 22 Aug 2022 19:39:56 +0200
Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in
task_numa_work. x86 CMPXCHG instruction returns success in ZF flag, so
this change saves a compare after cmpxchg (and related move instruction in
front of cmpxchg).
No functional change intended.
Link: https://lkml.kernel.org/r/20220822173956.82525-1-ubizjak@xxxxxxxxx
Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/sched/fair.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/sched/fair.c~sched-fair-use-try_cmpxchg-in-task_numa_work
+++ a/kernel/sched/fair.c
@@ -2964,7 +2964,7 @@ static void task_numa_work(struct callba
}
next_scan = now + msecs_to_jiffies(p->numa_scan_period);
- if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
+ if (!try_cmpxchg(&mm->numa_next_scan, &migrate, next_scan))
return;
/*
_
Patches currently in -mm which might be from ubizjak@xxxxxxxxx are
zram-use-try_cmpxchg-in-update_used_max.patch
llist-avoid-extra-memory-read-in-llist_add_batch.patch
sched-fair-use-try_cmpxchg-in-task_numa_work.patch
