linux-kernel - Re: [PATCH] sched/fair: fix use stale overloaded status to find busiest group

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Message-ID: <20141104105203.GM3337@twins.programming.kicks-ass.net>
Date:	Tue, 4 Nov 2014 11:52:03 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Wanpeng Li <wanpeng.li@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...hat.com>, Rik van Riel <riel@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Kirill Tkhai <ktkhai@...allels.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/fair: fix use stale overloaded status to find
 busiest group

On Tue, Nov 04, 2014 at 01:30:56PM +0800, Wanpeng Li wrote:
> Commit caeb178c60f4 ("sched/fair: Make update_sd_pick_busiest() return 
> 'true' on a busier sd") makes groups are ranked in the order overloaded > 
> imbalance > other and busiest group is picked according to this order. 
> sgs->group_capacity_factor is used to check if group is overloaded. In 
> the case of the child domain prefers tasks go to siblings first, the 
> sgs->group_capacity_factor will be set lower to one in order to move all 
> the excess tasks away. However, group overloaded status is not updated 
> in the case of sgs->group_capacity_factor be set lower to one which 
> leads to miss find the busiest group. This patch fix it by updating 
> group overloaded status in the case of sg capacity factor is set to 
> one in order to find busiest group accurately.

You noticed this while going over Vincents patches, right?

Also, try and introduce some newlines in the changelog, paragraphs of
3-5 lines are best.
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