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Date: Mon, 09 Jul 2012 11:27:53 +0900
From: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
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To: Johannes Weiner <hannes@cmpxchg.org>
CC: Andrew Morton <akpm@linux-foundation.org>, Michal Hocko <mhocko@suse.cz>,
        Hugh Dickins <hughd@google.com>, David Rientjes <rientjes@google.com>,
        linux-mm@kvack.org, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [patch 01/11] mm: memcg: fix compaction/migration failing due
 to memcg limits
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(2012/07/05 9:44), Johannes Weiner wrote:
> Compaction (and page migration in general) can currently be hindered
> through pages being owned by memory cgroups that are at their limits
> and unreclaimable.
> 
> The reason is that the replacement page is being charged against the
> limit while the page being replaced is also still charged.  But this
> seems unnecessary, given that only one of the two pages will still be
> in use after migration finishes.
> 
> This patch changes the memcg migration sequence so that the
> replacement page is not charged.  Whatever page is still in use after
> successful or failed migration gets to keep the charge of the page
> that was going to be replaced.
> 
> Reported-by: David Rientjes <rientjes@google.com>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>