korg/linux
0
0
Fork 0
mirror of https://mirrors.bfsu.edu.cn/git/linux.git synced 2024-11-11 12:28:41 +08:00
Code Issues Packages Projects Releases Wiki Activity

block: kill extra rcu lock/unlock in queue enter

Browse Source 
blk_try_enter_queue() already takes rcu_read_lock/unlock, so we can
avoid the second pair in percpu_ref_tryget_live(), use a newly added
percpu_ref_tryget_live_rcu().

As rcu_read_lock/unlock imply barrier()s, it's pretty noticeable,
especially for for !CONFIG_PREEMPT_RCU (default for some distributions),
where __rcu_read_lock/unlock() are not inlined.

3.20%  io_uring  [kernel.vmlinux]  [k] __rcu_read_unlock
3.05%  io_uring  [kernel.vmlinux]  [k] __rcu_read_lock

2.52%  io_uring  [kernel.vmlinux]  [k] __rcu_read_unlock
2.28%  io_uring  [kernel.vmlinux]  [k] __rcu_read_lock

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/6b11c67ea495ed9d44f067622d852de4a510ce65.1634822969.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2021-10-21 14:30:52 +01:00 committed by Jens Axboe
parent 3b13c16818
commit e94f68527a
1 changed files with 1 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
block/blk-core.c
View File

@ -389,7 +389,7 @@ EXPORT_SYMBOL(blk_cleanup_queue);
static bool blk_try_enter_queue(struct request_queue *q, bool pm)
{
rcu_read_lock();
if (!percpu_ref_tryget_live(&q->q_usage_counter))
if (!percpu_ref_tryget_live_rcu(&q->q_usage_counter))
goto fail;
/*