On Mon, 15 Jun 2020 at 16:20, Peng Wang <rocking@xxxxxxxxxxxxxxxxx> wrote:
While looking at enqueue_task_fair and dequeue_task_fair, it occurred
to me that dequeue_task_fair can also be optimized as Vincent described
in commit 7d148be69e3a ("sched/fair: Optimize enqueue_task_fair()").
good point
dequeue_throttle label can ensure se not to be NULL, and se is
always NULL when reaching root level.
Signed-off-by: Peng Wang <rocking@xxxxxxxxxxxxxxxxx>
---
kernel/sched/fair.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index cbcb2f7..e6be952 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5614,10 +5614,10 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
}
-dequeue_throttle:
- if (!se)
- sub_nr_running(rq, 1);
+ /* At this point se is NULL and we are at root level*/
+ sub_nr_running(rq, 1);
+dequeue_throttle:
/* balance early to pull high priority tasks */
if (unlikely(!was_sched_idle && sched_idle_rq(rq)))
rq->next_balance = jiffies;
You can move the label here because sched_idle_rq() uses
rq->nr-running and rq->cfs.idle_h_nr_running so they will not change
if we jump to the label before reaching root level
--
2.9.5