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From:   qianjun.kernel@gmail.com
To:     mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de
Cc:     linux-kernel@vger.kernel.org, jun qian <qianjun.kernel@gmail.com>
Subject: [PATCH 1/1] sched/fair:Reduce unnecessary check preempt in the sched tick
Date:   Tue, 13 Apr 2021 21:18:42 +0800
Message-Id: <20210413131842.44430-1-qianjun.kernel@gmail.com>
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From: jun qian <qianjun.kernel@gmail.com>

If it has been determined that the current cpu need resched in the
early stage of for_each_sched_entity, then there is no need to check
preempt in the subsequent se->parent entity_tick.

Signed-off-by: jun qian <qianjun.kernel@gmail.com>
---
 kernel/sched/fair.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1a68a0536add..c0d135100d54 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4352,8 +4352,13 @@ 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;
 
+	/* If the TIF_NEED_RESCHED has been set, it is no need to check again */
+	if (test_tsk_need_resched(rq->curr))
+		return;
+
 	ideal_runtime = sched_slice(cfs_rq, curr);
 	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
 	if (delta_exec > ideal_runtime) {
-- 
2.18.2