linux-kernel - Re: [PATCH 4/7] memcg : fix charge function of THP allocation.

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Message-ID: <20110127141837.GB14512@cmpxchg.org>
Date:	Thu, 27 Jan 2011 15:18:37 +0100
From:	Johannes Weiner <hannes@...xchg.org>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH 4/7] memcg : fix charge function of THP allocation.

On Thu, Jan 27, 2011 at 11:34:38AM +0100, Johannes Weiner wrote:
> On Fri, Jan 21, 2011 at 03:44:30PM +0900, KAMEZAWA Hiroyuki wrote:
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> > 
> > When THP is used, Hugepage size charge can happen. It's not handled
> > correctly in mem_cgroup_do_charge(). For example, THP can fallback
> > to small page allocation when HUGEPAGE allocation seems difficult
> > or busy, but memory cgroup doesn't understand it and continue to
> > try HUGEPAGE charging. And the worst thing is memory cgroup
> > believes 'memory reclaim succeeded' if limit - usage > PAGE_SIZE.
> > 
> > By this, khugepaged etc...can goes into inifinite reclaim loop
> > if tasks in memcg are busy.
> > 
> > After this patch 
> >  - Hugepage allocation will fail if 1st trial of page reclaim fails.
> >  - distinguish THP allocaton from Bached allocation. 
> 
> This does too many things at once.  Can you split this into more
> patches where each one has a single objective?  Thanks.

So I sent three patches that, I think, fix the same issues this patch
fixes, only they are much simpler.

The more I look at this code, though, the less confident I am in it..
Can you guys give it a good look?

Thanks,
	Hannes
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