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Date: Wed, 20 Oct 2010 23:35:15 +0900
From: Minchan Kim <minchan.kim@gmail.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Greg Thelen <gthelen@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        containers@lists.osdl.org, Andrea Righi <arighi@develer.com>,
        Balbir Singh <balbir@linux.vnet.ibm.com>,
        Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>,
        Ciju Rajan K <ciju@linux.vnet.ibm.com>,
        David Rientjes <rientjes@google.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
Message-ID: <20101020143515.GB5243@barrios-desktop>
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 <20101020122144.47f2b60b.kamezawa.hiroyu@jp.fujitsu.com>
 <20101020140255.5b8afb63.kamezawa.hiroyu@jp.fujitsu.com>
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On Wed, Oct 20, 2010 at 02:02:55PM +0900, KAMEZAWA Hiroyuki wrote:
> Fixed one here.
> ==
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.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@jp.fujitsu.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>

It should have written this on Documentation.
"memcg dirty limit can't exceed global dirty limit"

-- 
Kind regards,
Minchan Kim