linux-kernel - [patch v6 4/8] sched: fix slept time double counting in enqueue entity

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Date:	Fri, 10 May 2013 23:17:25 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	mingo@...hat.com, peterz@...radead.org, tglx@...utronix.de,
	akpm@...ux-foundation.org, bp@...en8.de, pjt@...gle.com,
	namhyung@...nel.org, efault@....de, morten.rasmussen@....com
Cc:	vincent.guittot@...aro.org, preeti@...ux.vnet.ibm.com,
	viresh.kumar@...aro.org, linux-kernel@...r.kernel.org,
	alex.shi@...el.com, mgorman@...e.de, riel@...hat.com,
	wangyun@...ux.vnet.ibm.com
Subject: [patch v6 4/8] sched: fix slept time double counting in enqueue entity

The wakeuped migrated task will __synchronize_entity_decay(se); in
migrate_task_fair, then it needs to set
`se->avg.last_runnable_update -= (-se->avg.decay_count) << 20'
before update_entity_load_avg, in order to avoid slept time is updated
twice for se.avg.load_avg_contrib in both __syncchronize and
update_entity_load_avg.

but if the slept task is waked up from self cpu, it miss the
last_runnable_update before update_entity_load_avg(se, 0, 1), then the
slept time was used twice in both functions.
So we need to remove the double slept time counting.

Signed-off-by: Alex Shi <alex.shi@...el.com>
---
 kernel/sched/fair.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 203f236..8cd19f3 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1551,7 +1551,8 @@ static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
 		}
 		wakeup = 0;
 	} else {
-		__synchronize_entity_decay(se);
+		se->avg.last_runnable_update += __synchronize_entity_decay(se)
+							<< 20;
 	}
 
 	/* migrated tasks did not contribute to our blocked load */
-- 
1.7.5.4

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