blk-throttle: Move service tree validation out of the throtl_rb_first() (2397611a) · Commits · 戴 / test

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:

Baolin Wang <baolin.wang@linux.alibaba.com> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

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;

Admin message