linux-kernel - Re: [patch] memcg: skip scanning active lists based on individual size

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Date:	Wed, 31 Aug 2011 14:27:34 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Johannes Weiner <jweiner@...hat.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Balbir Singh <bsingharora@...il.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] memcg: skip scanning active lists based on individual
 size

On 08/31/2011 05:08 AM, Johannes Weiner wrote:
> Reclaim decides to skip scanning an active list when the corresponding
> inactive list is above a certain size in comparison to leave the
> assumed working set alone while there are still enough reclaim
> candidates around.
>
> The memcg implementation of comparing those lists instead reports
> whether the whole memcg is low on the requested type of inactive
> pages, considering all nodes and zones.
>
> This can lead to an oversized active list not being scanned because of
> the state of the other lists in the memcg, as well as an active list
> being scanned while its corresponding inactive list has enough pages.
>
> Not only is this wrong, it's also a scalability hazard, because the
> global memory state over all nodes and zones has to be gathered for
> each memcg and zone scanned.
>
> Make these calculations purely based on the size of the two LRU lists
> that are actually affected by the outcome of the decision.
>
> Signed-off-by: Johannes Weiner<jweiner@...hat.com>
> Cc: Rik van Riel<riel@...hat.com>
> Cc: KOSAKI Motohiro<kosaki.motohiro@...fujitsu.com>
> Cc: KAMEZAWA Hiroyuki<kamezawa.hiroyu@...fujitsu.com>
> Cc: Daisuke Nishimura<nishimura@....nes.nec.co.jp>
> Cc: Balbir Singh<bsingharora@...il.com>

Reviewed-by: Rik van Riel <riel@...hat.com>

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