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authorUros Bizjak <ubizjak@gmail.com>2022-07-12 17:19:47 +0200
committerJens Axboe <axboe@kernel.dk>2022-07-12 15:45:31 -0600
commitaee8960c2eae12636040dbf0f04e135273b1612d (patch)
treeda17cc2655233b3460ba68c36a0ea92b47315094 /block
parent939f9dd040fe1063d884f8f0f89b037093fe2341 (diff)
blk-iolatency: Use atomic{,64}_try_cmpxchg
Use atomic_try_cmpxchg instead of atomic_cmpxchg (*ptr, old, new) == old in check_scale_change and atomic64_try_cmpxchg in blkcg_iolatency_done_bio. 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> Link: https://lore.kernel.org/r/20220712151947.6783-1-ubizjak@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
-rw-r--r--block/blk-iolatency.c12
1 files changed, 5 insertions, 7 deletions
diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index 9568bf8dfe82..79745c6d8e15 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -401,7 +401,6 @@ static void check_scale_change(struct iolatency_grp *iolat)
unsigned int cur_cookie;
unsigned int our_cookie = atomic_read(&iolat->scale_cookie);
u64 scale_lat;
- unsigned int old;
int direction = 0;
if (lat_to_blkg(iolat)->parent == NULL)
@@ -422,11 +421,10 @@ static void check_scale_change(struct iolatency_grp *iolat)
else
return;
- old = atomic_cmpxchg(&iolat->scale_cookie, our_cookie, cur_cookie);
-
- /* Somebody beat us to the punch, just bail. */
- if (old != our_cookie)
+ if (!atomic_try_cmpxchg(&iolat->scale_cookie, &our_cookie, cur_cookie)) {
+ /* Somebody beat us to the punch, just bail. */
return;
+ }
if (direction < 0 && iolat->min_lat_nsec) {
u64 samples_thresh;
@@ -633,8 +631,8 @@ static void blkcg_iolatency_done_bio(struct rq_qos *rqos, struct bio *bio)
window_start = atomic64_read(&iolat->window_start);
if (now > window_start &&
(now - window_start) >= iolat->cur_win_nsec) {
- if (atomic64_cmpxchg(&iolat->window_start,
- window_start, now) == window_start)
+ if (atomic64_try_cmpxchg(&iolat->window_start,
+ &window_start, now))
iolatency_check_latencies(iolat, now);
}
}