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authorBaolin Wang <baolin.wang@linux.alibaba.com>2020-10-08 06:52:27 +0300
committerJens Axboe <axboe@kernel.dk>2020-10-08 17:01:38 +0300
commit2397611ac802c4f8028b6b2e585b9857d2f8138b (patch)
tree860f4f541bbfaa27643a098bdc190422ea4814cb
parentb7b609de5a0835b2ca10c71df5d9570008eb1084 (diff)
downloadlinux-2397611ac802c4f8028b6b2e585b9857d2f8138b.tar.xz
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: Baolin Wang <baolin.wang@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--block/blk-throttle.c9
1 files changed, 5 insertions, 4 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index f1bcb5c320e8..38aed8baacf4 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -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;