From: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Date: Mon, 15 Oct 2007 15:00:12 +0000 (+0200)
Subject: sched: group scheduler, fix latency
X-Git-Tag: v2.6.24-rc1~1289^2~57
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b9fa3df33f9166daf81bfa8253d339f5a7726122;p=linux-2.6

sched: group scheduler, fix latency

There is a possibility that because of task of a group moving from one
cpu to another, it may gain more cpu time that desired. See
http://marc.info/?l=linux-kernel&m=119073197730334 for details.

This is an attempt to fix that problem. Basically it simulates dequeue
of higher level entities as if they are going to sleep. Similarly it
simulate wakeup of higher level entities as if they are waking up from
sleep.

Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
---

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 57e7f3672f..de13a6f5b9 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -727,6 +727,7 @@ static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
 			break;
 		cfs_rq = cfs_rq_of(se);
 		enqueue_entity(cfs_rq, se, wakeup);
+		wakeup = 1;
 	}
 }
 
@@ -746,6 +747,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep)
 		/* Don't dequeue parent if it has other entities besides us */
 		if (cfs_rq->load.weight)
 			break;
+		sleep = 1;
 	}
 }