Commit 2397611a authored by Baolin Wang's avatar Baolin Wang Committed by Jens Axboe
Browse files

blk-throttle: Move service tree validation out of the throtl_rb_first() 



The throtl_schedule_next_dispatch() will validate if the service queue
is empty before calling update_min_dispatch_time(), and the
update_min_dispatch_time() will call throtl_rb_first(), which will
validate service queue again.

Thus we can move the service queue validation out of the
throtl_rb_first() to remove the redundant validation in the fast path.

Signed-off-by: default avatarBaolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent b7b609de

block/blk-throttle.c

+5 −4
Original line number Diff line number Diff line
@@ -638,9 +638,6 @@ static struct throtl_grp * 
throtl_rb_first(struct throtl_service_queue *parent_sq)

{

	struct rb_node *n;

	/* Service tree is empty */

	if (!parent_sq->nr_pending)

		return NULL;



	n = rb_first_cached(&parent_sq->pending_tree);

	WARN_ON_ONCE(!n);
@@ -1224,9 +1221,13 @@ static int throtl_select_dispatch(struct throtl_service_queue *parent_sq) 
	unsigned int nr_disp = 0;



	while (1) {

		struct throtl_grp *tg = throtl_rb_first(parent_sq);

		struct throtl_grp *tg;

		struct throtl_service_queue *sq;



		if (!parent_sq->nr_pending)

			break;



		tg = throtl_rb_first(parent_sq);

		if (!tg)

			break;