Commit 0c0be98b authored by Yu Kuai's avatar Yu Kuai Committed by Song Liu
Browse files

md/raid10: prevent unnecessary calls to wake_up() in fast path 



Currently, wake_up() is called unconditionally in fast path such as
raid10_make_request(), which will cause lock contention under high
concurrency:

raid10_make_request
 wake_up
  __wake_up_common_lock
   spin_lock_irqsave

Improve performance by only call wake_up() if waitqueue is not empty
in allow_barrier() and raid10_make_request().

Signed-off-by: default avatarYu Kuai <yukuai3@huawei.com>
Reviewed-by: default avatarLogan Gunthorpe <logang@deltatee.com>
Acked-by: default avatarGuoqing Jiang <guoqing.jiang@linux.dev>
Signed-off-by: default avatarSong Liu <song@kernel.org>
parent 0de57e54

drivers/md/raid10.c

+8 −2
Original line number Diff line number Diff line
@@ -274,6 +274,12 @@ static void put_buf(struct r10bio *r10_bio) 
	lower_barrier(conf);

}



static void wake_up_barrier(struct r10conf *conf)

{

	if (wq_has_sleeper(&conf->wait_barrier))

		wake_up(&conf->wait_barrier);

}



static void reschedule_retry(struct r10bio *r10_bio)

{

	unsigned long flags;
@@ -1015,7 +1021,7 @@ static void allow_barrier(struct r10conf *conf) 
{

	if ((atomic_dec_and_test(&conf->nr_pending)) ||

			(conf->array_freeze_pending))

		wake_up(&conf->wait_barrier);

		wake_up_barrier(conf);

}



static void freeze_array(struct r10conf *conf, int extra)
@@ -1891,7 +1897,7 @@ static bool raid10_make_request(struct mddev *mddev, struct bio *bio) 
	__make_request(mddev, bio, sectors);



	/* In case raid10d snuck in to freeze_array */

	wake_up(&conf->wait_barrier);

	wake_up_barrier(conf);

	return true;

}