linux-kernel - Re: [patch 2/3] memcg: prevent endless loop when charging huge pages to near-limit group

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Message-ID: <AANLkTikdrFYCjYTat+0iLoOJD9S1=KreJhNbFXbzah4x@mail.gmail.com>
Date:	Tue, 1 Feb 2011 07:42:48 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	akpm@...ux-foundation.org, kamezawa.hiroyu@...fujitsu.com,
	nishimura@....nes.nec.co.jp, balbir@...ux.vnet.ibm.com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 2/3] memcg: prevent endless loop when charging huge pages
 to near-limit group

On Mon, Jan 31, 2011 at 11:03 PM, Johannes Weiner <hannes@...xchg.org> wrote:
> If reclaim after a failed charging was unsuccessful, the limits are
> checked again, just in case they settled by means of other tasks.
>
> This is all fine as long as every charge is of size PAGE_SIZE, because
> in that case, being below the limit means having at least PAGE_SIZE
> bytes available.
>
> But with transparent huge pages, we may end up in an endless loop
> where charging and reclaim fail, but we keep going because the limits
> are not yet exceeded, although not allowing for a huge page.
>
> Fix this up by explicitely checking for enough room, not just whether
> we are within limits.
>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
Reviewed-by: Minchan Kim <minchan.kim@...il.com>


-- 
Kind regards,
Minchan Kim
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