* [PATCH] sched/clock: Use try_cmpxchg64 in sched_clock_{local,remote}
@ 2022-05-18 18:49 Uros Bizjak
2022-05-19 7:47 ` Peter Zijlstra
2022-05-19 21:49 ` [tip: locking/core] " tip-bot2 for Uros Bizjak
0 siblings, 2 replies; 3+ messages in thread
From: Uros Bizjak @ 2022-05-18 18:49 UTC (permalink / raw)
To: linux-kernel
Cc: Uros Bizjak, Ingo Molnar, Peter Zijlstra, Juri Lelli,
Vincent Guittot, Dietmar Eggemann, Steven Rostedt, Ben Segall,
Mel Gorman, Daniel Bristot de Oliveira
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] sched/clock: Use try_cmpxchg64 in sched_clock_{local,remote}
2022-05-18 18:49 [PATCH] sched/clock: Use try_cmpxchg64 in sched_clock_{local,remote} Uros Bizjak
@ 2022-05-19 7:47 ` Peter Zijlstra
2022-05-19 21:49 ` [tip: locking/core] " tip-bot2 for Uros Bizjak
1 sibling, 0 replies; 3+ messages in thread
From: Peter Zijlstra @ 2022-05-19 7:47 UTC (permalink / raw)
To: Uros Bizjak
Cc: linux-kernel, Ingo Molnar, Juri Lelli, Vincent Guittot,
Dietmar Eggemann, Steven Rostedt, Ben Segall, Mel Gorman,
Daniel Bristot de Oliveira
On Wed, May 18, 2022 at 08:49:53PM +0200, Uros Bizjak wrote:
> 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>
Thanks!
^ permalink raw reply [flat|nested] 3+ messages in thread
* [tip: locking/core] sched/clock: Use try_cmpxchg64 in sched_clock_{local,remote}
2022-05-18 18:49 [PATCH] sched/clock: Use try_cmpxchg64 in sched_clock_{local,remote} Uros Bizjak
2022-05-19 7:47 ` Peter Zijlstra
@ 2022-05-19 21:49 ` tip-bot2 for Uros Bizjak
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot2 for Uros Bizjak @ 2022-05-19 21:49 UTC (permalink / raw)
To: linux-tip-commits; +Cc: Uros Bizjak, Peter Zijlstra (Intel), x86, linux-kernel
The following commit has been merged into the locking/core branch of tip:
Commit-ID: 8491d1bdf5de152f27fc941e2dcdc4e66c950542
Gitweb: https://git.kernel.org/tip/8491d1bdf5de152f27fc941e2dcdc4e66c950542
Author: Uros Bizjak <ubizjak@gmail.com>
AuthorDate: Wed, 18 May 2022 20:49:53 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Thu, 19 May 2022 23:46:09 +02:00
sched/clock: Use try_cmpxchg64 in sched_clock_{local,remote}
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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220518184953.3446778-1-ubizjak@gmail.com
---
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 d9272d9..e374c0c 100644
--- a/kernel/sched/clock.c
+++ b/kernel/sched/clock.c
@@ -287,7 +287,7 @@ again:
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 @@ again:
val = remote_clock;
}
- if (cmpxchg64(ptr, old_val, val) != old_val)
+ if (!try_cmpxchg64(ptr, &old_val, val))
goto again;
return val;
^ permalink raw reply related [flat|nested] 3+ messages in thread
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2022-05-18 18:49 [PATCH] sched/clock: Use try_cmpxchg64 in sched_clock_{local,remote} Uros Bizjak
2022-05-19 7:47 ` Peter Zijlstra
2022-05-19 21:49 ` [tip: locking/core] " tip-bot2 for Uros Bizjak
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