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| author |   Uros Bizjak <ubizjak@gmail.com> | 2022-07-12 17:19:47 +0200 |
|---|---|---|
| committer |   Jens Axboe <axboe@kernel.dk> | 2022-07-12 15:45:31 -0600 |
| commit | aee8960c2eae12636040dbf0f04e135273b1612d (patch) | |
| tree | da17cc2655233b3460ba68c36a0ea92b47315094 /block | |
| parent | block: Use try_cmpxchg in update_io_ticks (diff) | |
| download | linux-dev-aee8960c2eae12636040dbf0f04e135273b1612d.tar.xz linux-dev-aee8960c2eae12636040dbf0f04e135273b1612d.zip | |
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.c | 12 |
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); } } |