From: Uros Bizjak <ubizjak@gmail.com>
To: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Uros Bizjak <ubizjak@gmail.com>, Jens Axboe <axboe@kernel.dk>
Subject: [PATCH v2] block: Use try_cmpxchg in update_io_ticks
Date: Tue, 12 Jul 2022 17:27:41 +0200 [thread overview]
Message-ID: <20220712152741.7324-1-ubizjak@gmail.com> (raw)
Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in
update_io_ticks. 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.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
---
v2: Split patch from the original big patch
---
block/blk-core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 27fb1357ad4b..628b965356db 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -987,7 +987,7 @@ void update_io_ticks(struct block_device *part, unsigned long now, bool end)
again:
stamp = READ_ONCE(part->bd_stamp);
if (unlikely(time_after(now, stamp))) {
- if (likely(cmpxchg(&part->bd_stamp, stamp, now) == stamp))
+ if (likely(try_cmpxchg(&part->bd_stamp, &stamp, now)))
__part_stat_add(part, io_ticks, end ? now - stamp : 1);
}
if (part->bd_partno) {
--
2.35.3
next reply other threads:[~2022-07-12 15:27 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-12 15:27 Uros Bizjak [this message]
2022-07-12 20:40 ` [PATCH v2] block: Use try_cmpxchg in update_io_ticks Jens Axboe
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