linux-kernel - Re: [PATCH v2][memcg+dirtylimit] Fix overwriting global vm dirty limit setting by memcg (Re: [PATCH v3 00/11] memcg: per cgroup dirty page accounting

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Message-Id: <20101021091029.48082934.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 21 Oct 2010 09:10:29 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	Greg Thelen <gthelen@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	containers@...ts.osdl.org, Andrea Righi <arighi@...eler.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Ciju Rajan K <ciju@...ux.vnet.ibm.com>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH v2][memcg+dirtylimit] Fix  overwriting global vm dirty
 limit setting by memcg (Re: [PATCH v3 00/11] memcg: per cgroup dirty page
 accounting

On Wed, 20 Oct 2010 23:35:15 +0900
Minchan Kim <minchan.kim@...il.com> wrote:

> On Wed, Oct 20, 2010 at 02:02:55PM +0900, KAMEZAWA Hiroyuki wrote:
> > Fixed one here.
> > ==
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> > 
> > Now, at calculating dirty limit, vm_dirty_param() is called.
> > This function returns dirty-limit related parameters considering
> > memory cgroup settings.
> > 
> > Now, assume that vm_dirty_bytes=100M (global dirty limit) and
> > memory cgroup has 1G of pages and 40 dirty_ratio, dirtyable memory is
> > 500MB.
> > 
> > In this case, global_dirty_limits will consider dirty_limt as
> > 500 *0.4 = 200MB. This is bad...memory cgroup is not back door.
> > 
> > This patch limits the return value of vm_dirty_param() considring
> > global settings.
> > 
> > Changelog:
> >  - fixed an argument "mem" int to u64
> >  - fixed to use global available memory to cap memcg's value.
> > 
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Reviewed-by: Minchan Kim <minchan.kim@...il.com>
> 
> It should have written this on Documentation.
> "memcg dirty limit can't exceed global dirty limit"
> 
Sure. Anyway we need review & rewrite Documenation after dirty limit
merged. (I think Greg will do much.)

Thanks,
-Kame

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