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

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Date:	Tue, 04 Nov 2014 19:08:23 +0800
From:	Wanpeng Li <kernellwp@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	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

Hi Peter,
On 14/11/4 下午6:52, Peter Zijlstra wrote:
> 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?

Indeed. ;-)

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

Ok, I will send a new version tomorrow. ;-)

Regards,
Wanpeng Li

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