+ sched-fair-use-try_cmpxchg-in-task_numa_work.patch added to mm-nonmm-unstable branch

+ sched-fair-use-try_cmpxchg-in-task_numa_work.patch added to mm-nonmm-unstable branch

[Andrew Morton]

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

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------------------------------------------------------
From: Uros Bizjak <ubizjak@gmail.com>
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@gmail.com
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 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@gmail.com 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