From: Uros Bizjak <ubizjak@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: Uros Bizjak <ubizjak@gmail.com>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>
Subject: [PATCH] sched/fair: Use try_cmpxchg in task_numa_work
Date: Mon, 22 Aug 2022 19:39:56 +0200 [thread overview]
Message-ID: <20220822173956.82525-1-ubizjak@gmail.com> (raw)
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.
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: Uros Bizjak <ubizjak@gmail.com>
---
kernel/sched/fair.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 914096c5b1ae..efe73ee89989 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2802,7 +2802,7 @@ static void task_numa_work(struct callback_head *work)
}
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;
/*
--
2.37.1
reply other threads:[~2022-08-22 17:40 UTC|newest]
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