linux-kernel - [PATCH V2 1/1] sched/fair:Reduce unnecessary check preempt in the sched tick

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Date:   Wed, 14 Apr 2021 10:22:29 +0800
From:   qianjun.kernel@...il.com
To:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com
Cc:     linux-kernel@...r.kernel.org, jun qian <qianjun.kernel@...il.com>
Subject: [PATCH V2 1/1] sched/fair:Reduce unnecessary check preempt in the sched tick

From: jun qian <qianjun.kernel@...il.com>

As you are already set the TIF_NEED_RESCHED, there is no need
to check resched again.

Signed-off-by: jun qian <qianjun.kernel@...il.com>
---
 kernel/sched/fair.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 794c2cb945f8..1a69b5fffe4a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4360,19 +4360,26 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
 {
 	unsigned long ideal_runtime, delta_exec;
 	struct sched_entity *se;
+	struct rq *rq = rq_of(cfs_rq);
 	s64 delta;
 
 	ideal_runtime = sched_slice(cfs_rq, curr);
 	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
 	if (delta_exec > ideal_runtime) {
-		resched_curr(rq_of(cfs_rq));
+		if (!test_tsk_need_resched(rq->curr))
+			resched_curr(rq_of(cfs_rq));
 		/*
 		 * The current task ran long enough, ensure it doesn't get
 		 * re-elected due to buddy favours.
 		 */
 		clear_buddies(cfs_rq, curr);
 		return;
-	}
+	/*
+	 * If here with TIF_NEED_RESCHED already set from the early entity_tick,
+	 * there is no need to check again.
+	 */
+	} else if (test_tsk_need_resched(rq->curr))
+		return;
 
 	/*
 	 * Ensure that a task that missed wakeup preemption by a
-- 
2.18.2