linux-kernel - [PATCH v2] sched/rt: Make update_curr

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Date:   Tue, 6 Feb 2018 09:53:28 +0800
From:   Wen Yang <wen.yang99@....com.cn>
To:     mingo@...hat.com, peterz@...radead.org
Cc:     linux-kernel@...r.kernel.org, jiang.biao2@....com.cn,
        zhong.weidong@....com.cn, wen.yang99@....com.cn
Subject: [PATCH v2] sched/rt: Make update_curr_rt() more accurate

rq->clock_task may be updated between the two calls of
rq_clock_task() in update_curr_rt(). Calling rq_clock_task() only
once makes it more accurate and efficient, taking update_curr() as
reference.

Signed-off-by: Wen Yang <wen.yang99@....com.cn>
Reviewed-by: Jiang Biao <jiang.biao2@....com.cn>
---
 kernel/sched/rt.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 665ace2..fc527b1 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -951,11 +951,13 @@ static void update_curr_rt(struct rq *rq)
 	struct task_struct *curr = rq->curr;
 	struct sched_rt_entity *rt_se = &curr->rt;
 	u64 delta_exec;
+	u64 now;
 
 	if (curr->sched_class != &rt_sched_class)
 		return;
 
-	delta_exec = rq_clock_task(rq) - curr->se.exec_start;
+	now = rq_clock_task(rq);
+	delta_exec = now - curr->se.exec_start;
 	if (unlikely((s64)delta_exec <= 0))
 		return;
 
@@ -968,7 +970,7 @@ static void update_curr_rt(struct rq *rq)
 	curr->se.sum_exec_runtime += delta_exec;
 	account_group_exec_runtime(curr, delta_exec);
 
-	curr->se.exec_start = rq_clock_task(rq);
+	curr->se.exec_start = now;
 	cgroup_account_cputime(curr, delta_exec);
 
 	sched_rt_avg_update(rq, delta_exec);
-- 
1.8.3.1