linux-kernel - [PATCH v5 4/5] sched/fair: Skip detach sched avgs for new task when changing task groups

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Message-Id: <1465427754-28897-5-git-send-email-yuyang.du@intel.com>
Date:	Thu,  9 Jun 2016 07:15:53 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	peterz@...radead.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org
Cc:	bsegall@...gle.com, pjt@...gle.com, morten.rasmussen@....com,
	vincent.guittot@...aro.org, dietmar.eggemann@....com,
	matt@...eblueprint.co.uk, Yuyang Du <yuyang.du@...el.com>
Subject: [PATCH v5 4/5] sched/fair: Skip detach sched avgs for new task when changing task groups

Newly forked task has not been enqueued, so should not be removed from
cfs_rq in task_move_group_fair(). To do so, we identify newly forked
tasks by their sched_avg's last_update_time in detach_entity_load_avg().

Signed-off-by: Yuyang Du <yuyang.du@...el.com>
---
 kernel/sched/fair.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6e870c6..e0f219b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2943,6 +2943,10 @@ static inline void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_en
 
 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
+	/* Newly forked tasks are not attached yet. */
+	if (!se->avg.last_update_time)
+		return;
+
 	__update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
 			  &se->avg, se->on_rq * scale_load_down(se->load.weight),
 			  cfs_rq->curr == se, NULL);
-- 
1.7.9.5