linux-kernel - Re: [RFC][PATCH] avoid swapping out with swappiness==0

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Date:	Mon, 07 May 2012 16:11:23 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Satoru Moriya <satoru.moriya@....com>
CC:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"lwoodman@...hat.com" <lwoodman@...hat.com>,
	"jweiner@...hat.com" <jweiner@...hat.com>,
	"shaohua.li@...el.com" <shaohua.li@...el.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	Seiji Aguchi <seiji.aguchi@....com>
Subject: Re: [RFC][PATCH] avoid swapping out with swappiness==0

On 03/02/2012 12:36 PM, Satoru Moriya wrote:
> Sometimes we'd like to avoid swapping out anonymous memory
> in particular, avoid swapping out pages of important process or
> process groups while there is a reasonable amount of pagecache
> on RAM so that we can satisfy our customers' requirements.
>
> OTOH, we can control how aggressive the kernel will swap memory pages
> with /proc/sys/vm/swappiness for global and
> /sys/fs/cgroup/memory/memory.swappiness for each memcg.
>
> But with current reclaim implementation, the kernel may swap out
> even if we set swappiness==0 and there is pagecache on RAM.
>
> This patch changes the behavior with swappiness==0. If we set
> swappiness==0, the kernel does not swap out completely
> (for global reclaim until the amount of free pages and filebacked
> pages in a zone has been reduced to something very very small
> (nr_free + nr_filebacked<  high watermark)).

> Signed-off-by: Satoru Moriya<satoru.moriya@....com>

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

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