linux-kernel - Re: [patch 01/18] sched: (fixlet) dont update shares twice on on

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Message-ID: <20110722110627.GA20315@linux.vnet.ibm.com>
Date:	Fri, 22 Jul 2011 16:36:27 +0530
From:	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.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 <bsingharora@...il.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Ingo Molnar <mingo@...e.hu>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Jason Baron <jbaron@...hat.com>
Subject: Re: [patch 01/18] sched: (fixlet) dont update shares twice on on_rq
 parent

* Paul Turner <pjt@...gle.com> [2011-07-21 09:43:26]:

> 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 as we continue the shares update traversal from this 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 |    3 +++
>  1 file changed, 3 insertions(+)
> 
> Index: tip/kernel/sched_fair.c
> ===================================================================
> --- tip.orig/kernel/sched_fair.c
> +++ tip/kernel/sched_fair.c
> @@ -1370,6 +1370,9 @@ static void dequeue_task_fair(struct rq 
>  			 */
>  			if (task_sleep && parent_entity(se))
>  				set_next_buddy(parent_entity(se));
> +
> +			/* avoid re-evaluating load for this entity */
> +			se = parent_entity(se);
>  			break;
>  		}
>  		flags |= DEQUEUE_SLEEP;
> 
this patch has been merged into tip

commit 9598c82dcacadc3b9daa8170613fd054c6124d30
Author: Paul Turner <pjt@...gle.com>
Date:   Wed Jul 6 22:30:37 2011 -0700

    sched: Don't update shares twice on on_rq parent

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