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>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>
Subject: [PATCH] sched/clock: Use try_cmpxchg64 in sched_clock_{local,remote}
Date: Wed, 18 May 2022 20:49:53 +0200 [thread overview]
Message-ID: <20220518184953.3446778-1-ubizjak@gmail.com> (raw)
Use try_cmpxchg64 instead of cmpxchg64 (*ptr, old, new) != old in
sched_clock_{local,remote}. x86 cmpxchg returns success in ZF flag,
so this change saves a compare after cmpxchg (and related move
instruction in front of cmpxchg).
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>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
---
Patch requires commits 0aa7be05d83cc584da0782405e8007e351dfb6cc
and c2df0a6af177b6c06a859806a876f92b072dc624 from tip.git
---
kernel/sched/clock.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c
index d9272d9061a3..e374c0c923da 100644
--- a/kernel/sched/clock.c
+++ b/kernel/sched/clock.c
@@ -287,7 +287,7 @@ notrace static u64 sched_clock_local(struct sched_clock_data *scd)
clock = wrap_max(clock, min_clock);
clock = wrap_min(clock, max_clock);
- if (cmpxchg64(&scd->clock, old_clock, clock) != old_clock)
+ if (!try_cmpxchg64(&scd->clock, &old_clock, clock))
goto again;
return clock;
@@ -349,7 +349,7 @@ notrace static u64 sched_clock_remote(struct sched_clock_data *scd)
val = remote_clock;
}
- if (cmpxchg64(ptr, old_val, val) != old_val)
+ if (!try_cmpxchg64(ptr, &old_val, val))
goto again;
return val;
--
2.35.1
next reply other threads:[~2022-05-18 18:50 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-18 18:49 Uros Bizjak [this message]
2022-05-19 7:47 ` [PATCH] sched/clock: Use try_cmpxchg64 in sched_clock_{local,remote} Peter Zijlstra
2022-05-19 21:49 ` [tip: locking/core] " tip-bot2 for Uros Bizjak
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220518184953.3446778-1-ubizjak@gmail.com \
--to=ubizjak@gmail.com \
--cc=bristot@redhat.com \
--cc=bsegall@google.com \
--cc=dietmar.eggemann@arm.com \
--cc=juri.lelli@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=vincent.guittot@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.