diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2022-10-18 16:51:54 +0200 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2022-11-08 17:37:13 -0800 |
| commit | 70ec04f3486103819807b061b50a99f6e1d2bf36 (patch) | |
| tree | 21d513186676f0f3b97bfacb075675b1733b45e4 /drivers/block | |
| parent | 9fb6beea79c6e7c959adf4fb7b94cf9a6028b941 (diff) | |
| download | linux-stable-70ec04f3486103819807b061b50a99f6e1d2bf36.tar.gz linux-stable-70ec04f3486103819807b061b50a99f6e1d2bf36.tar.bz2 linux-stable-70ec04f3486103819807b061b50a99f6e1d2bf36.zip | |
zram: use try_cmpxchg in update_used_max
Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in
update_used_max. x86 CMPXCHG instruction returns success in ZF flag, so
this change saves a compare after cmpxchg (and related move instruction in
front of cmpxchg).
Also, reorder code a bit to remove additional compare and conditional jump
from the assembly code. Together, hese two changes save 15 bytes from the
function when compiled for x86_64.
No functional change intended.
Link: https://lkml.kernel.org/r/20221018145154.3699-1-ubizjak@gmail.com
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'drivers/block')
| -rw-r--r-- | drivers/block/zram/zram_drv.c | 13 |
1 files changed, 5 insertions, 8 deletions
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 966aab902d19..87711ddf4b54 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -188,16 +188,13 @@ static void update_position(u32 *index, int *offset, struct bio_vec *bvec) static inline void update_used_max(struct zram *zram, const unsigned long pages) { - unsigned long old_max, cur_max; - - old_max = atomic_long_read(&zram->stats.max_used_pages); + unsigned long cur_max = atomic_long_read(&zram->stats.max_used_pages); do { - cur_max = old_max; - if (pages > cur_max) - old_max = atomic_long_cmpxchg( - &zram->stats.max_used_pages, cur_max, pages); - } while (old_max != cur_max); + if (cur_max >= pages) + return; + } while (!atomic_long_try_cmpxchg(&zram->stats.max_used_pages, + &cur_max, pages)); } static inline void zram_fill_page(void *ptr, unsigned long len, |