linux-kernel - [PATCH] sched/deadline: Remove redundant code replenishing runtime

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Date:   Fri, 10 Feb 2017 18:11:28 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     peterz@...radead.org, mingo@...nel.org
Cc:     linux-kernel@...r.kernel.org, tkhai@...dex.ru
Subject: [PATCH] sched/deadline: Remove redundant code replenishing runtime

For a task passing its deadline while !rq, it will be replenished
in the following path because dl_se->deadline < rq_lock.

   enqueue_dl_entity(ENQUEUE_WAKEUP)
      update_dl_entity

Therefore, code replenishing it in the timer callback in the case is
unnecessary. This is not for enhancing performance but just for removing
a redundant code.

Signed-off-by: Byungchul Park <byungchul.park@....com>
---
 kernel/sched/deadline.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 27737f3..9c77696 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -624,10 +624,8 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
 	 * We can be both throttled and !queued. Replenish the counter
 	 * but do not enqueue -- wait for our wakeup to do that.
 	 */
-	if (!task_on_rq_queued(p)) {
-		replenish_dl_entity(dl_se, dl_se);
+	if (!task_on_rq_queued(p))
 		goto unlock;
-	}
 
 #ifdef CONFIG_SMP
 	if (unlikely(!rq->online)) {
-- 
1.9.1