linux-kernel - Re: [patch 01/15] sched: (fixlet) dont update shares twice on on

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Date:	Tue, 10 May 2011 16:14:10 +0900
From:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
To:	Paul Turner <pjt@...gle.com>
CC:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Bharata B Rao <bharata@...ux.vnet.ibm.com>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>, Pavel Emelyanov <xemul@...nvz.org>
Subject: Re: [patch 01/15] sched: (fixlet) dont update shares twice on on_rq
 parent

(2011/05/03 18:28), Paul Turner wrote:
> In dequeue_task_fair() we bail on dequeue when we encounter a parenting entity
> with additional weight.  However, we perform a double shares update on this
> entity since we continue the shares update traversal from that point, despite
> dequeue_entity() having already updated its queuing cfs_rq.
> 
> Avoid this by starting from the parent when we resume.
> 
> Signed-off-by: Paul Turner <pjt@...gle.com>
> ---
>  kernel/sched_fair.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> Index: tip/kernel/sched_fair.c
> ===================================================================
> --- tip.orig/kernel/sched_fair.c
> +++ tip/kernel/sched_fair.c
> @@ -1355,8 +1355,10 @@ static void dequeue_task_fair(struct rq 
>  		dequeue_entity(cfs_rq, se, flags);
>  
>  		/* Don't dequeue parent if it has other entities besides us */
> -		if (cfs_rq->load.weight)
> +		if (cfs_rq->load.weight) {
> +			se = parent_entity(se);
>  			break;
> +		}
>  		flags |= DEQUEUE_SLEEP;
>  	}
>  

Reviewed-by: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>

This small fixlet can stand alone.
Peter, how about getting this into git tree first?


Thanks,
H.Seto

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