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 <[email protected]> --- block/blk-throttle.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/block/blk-throttle.c b/block/blk-throttle.c index f1bcb5c..38aed8b 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -638,9 +638,6 @@ static void throtl_pd_free(struct blkg_policy_data *pd) 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; -- 1.8.3.1
