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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Mel Gorman <mel@csn.ul.ie>
Subject: Re: [PATCH 02/11] mm,migration: Do not try to migrate unmapped anonymous pages
Cc: kosaki.motohiro@jp.fujitsu.com, Minchan Kim <minchan.kim@gmail.com>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Andrew Morton <akpm@linux-foundation.org>,
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       David Rientjes <rientjes@google.com>, Rik van Riel <riel@redhat.com>,
       linux-kernel@vger.kernel.org, linux-mm@kvack.org
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Date: Fri, 19 Mar 2010 15:21:41 +0900 (JST)
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> > then, this logic depend on SLAB_DESTROY_BY_RCU, not refcount.
> > So, I think we don't need your [1/11] patch.
> > 
> > Am I missing something?
> > 
> 
> The refcount is still needed. The anon_vma might be valid, but the
> refcount is what ensures that the anon_vma is not freed and reused.

please please why do we need both mechanism. now cristoph is very busy and I am
de fact reviewer of page migration and mempolicy code. I really hope to understand
your patch.