linux-kernel - Re: [patch 08/11] mm: memcg: remove needless !mm fixup to init

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Date:	Tue, 10 Jul 2012 18:22:50 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Wanpeng Li <liwp.linux@...il.com>
Cc:	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 08/11] mm: memcg: remove needless !mm fixup to init_mm
 when charging

On Tue 10-07-12 14:54:48, Wanpeng Li wrote:
> On Tue, Jul 10, 2012 at 08:21:04AM +0200, Michal Hocko wrote:
> >On Tue 10-07-12 14:10:21, Wanpeng Li wrote:
> >> On Mon, Jul 09, 2012 at 05:20:58PM +0200, Michal Hocko wrote:
> >> >On Thu 05-07-12 02:45:00, Johannes Weiner wrote:
> >> >> It does not matter to __mem_cgroup_try_charge() if the passed mm is
> >> >> NULL or init_mm, it will charge the root memcg in either case.
> >> 
> >> You can also change the comment in __mem_cgroup_try_charge :
> >> 
> >> "if so charge the init_mm" => "if so charge the root memcg"
> >
> >This is already in place:
> >"
> >If mm is NULL and the caller doesn't pass a valid memcg pointer, that is
> >treated as a charge to root_mem_cgroup.
> >"
> 
> IIUC, if still keep comment "if so charge the init_mm" is not correct,
> since pages in pagecache aren't mapped into any processes' ptes, 
> so mm is NULL, and these pages which in pagecache are not belong 
> to init_mm, the comment should be changed. :-)

Fair enough. I guess Johannes will change that in the next post.
-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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