linux-kernel - [PATCH] sched: fix lose fair sleeper bonus in switch_to

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Date:	Mon, 7 Sep 2015 17:45:20 +0800
From:	Wanpeng Li <wanpeng.li@...mail.com>
To:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
CC:	linux-kernel@...r.kernel.org, Wanpeng Li <wanpeng.li@...mail.com>
Subject: [PATCH] sched: fix lose fair sleeper bonus in switch_to_fair()

The sleeper task will be normalized when moved from fair_sched_class, in 
order that vruntime will be adjusted either the task is running or sleeping 
when moved back. The nomalization in switch_to_fair for sleep task will 
result in lose fair sleeper bonus in place_entity() once the vruntime - 
cfs_rq->min_vruntime is big when moved from fair_sched_class.

This patch fix it by adjusting vruntime just during migrating as original 
codes since the vruntime of the task has usually NOT been normalized in 
this case.

Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
---
 kernel/sched/fair.c |   11 +++++++----
 1 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d26d3b7..eb9aa35 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8005,9 +8005,6 @@ static void attach_task_cfs_rq(struct task_struct *p)
 
 	/* Synchronize task with its cfs_rq */
 	attach_entity_load_avg(cfs_rq, se);
-
-	if (!vruntime_normalized(p))
-		se->vruntime += cfs_rq->min_vruntime;
 }
 
 static void switched_from_fair(struct rq *rq, struct task_struct *p)
@@ -8066,14 +8063,20 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
 #ifdef CONFIG_FAIR_GROUP_SCHED
 static void task_move_group_fair(struct task_struct *p)
 {
+	struct sched_entity *se = &p->se;
+	struct cfs_rq *cfs_rq = cfs_rq_of(se);
+
 	detach_task_cfs_rq(p);
 	set_task_rq(p, task_cpu(p));
 
 #ifdef CONFIG_SMP
 	/* Tell se's cfs_rq has been changed -- migrated */
-	p->se.avg.last_update_time = 0;
+	se->avg.last_update_time = 0;
 #endif
 	attach_task_cfs_rq(p);
+
+	if (!vruntime_normalized(p))
+		se->vruntime += cfs_rq->min_vruntime;
 }
 
 void free_fair_sched_group(struct task_group *tg)
-- 
1.7.1

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