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Date: Fri, 14 Aug 2009 09:19:35 -0400
From: Rik van Riel <riel@redhat.com>
Organization: Red Hat, Inc
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To: Wu Fengguang <fengguang.wu@intel.com>
CC: Johannes Weiner <hannes@cmpxchg.org>, Avi Kivity <avi@redhat.com>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Andrea Arcangeli <aarcange@redhat.com>,
       "Dike, Jeffrey G" <jeffrey.g.dike@intel.com>,
       "Yu, Wilfred" <wilfred.yu@intel.com>,
       "Kleen, Andi" <andi.kleen@intel.com>,
       Hugh Dickins <hugh.dickins@tiscali.co.uk>,
       Andrew Morton <akpm@linux-foundation.org>,
       Christoph Lameter <cl@linux-foundation.org>, Mel Gorman <mel@csn.ul.ie>,
       LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>
Subject: Re: [RFC] respect the referenced bit of KVM guest pages?
References: <20090812074820.GA29631@localhost> <4A82D24D.6020402@redhat.com> <20090813010356.GA7619@localhost> <4A843565.3010104@redhat.com> <4A843B72.6030204@redhat.com> <4A843EAE.6070200@redhat.com> <4A846581.2020304@redhat.com> <20090813211626.GA28274@cmpxchg.org> <4A850F4A.9020507@redhat.com> <20090814091055.GA29338@cmpxchg.org> <20090814095106.GA3345@localhost>
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Wu Fengguang wrote:
> On Fri, Aug 14, 2009 at 05:10:55PM +0800, Johannes Weiner wrote:

>> So even with the active list being a FIFO, we keep usage information
>> gathered from the inactive list.  If we deactivate pages in arbitrary
>> list intervals, we throw this away.
> 
> We do have the danger of FIFO, if inactive list is small enough, so
> that (unconditionally) deactivated pages quickly get reclaimed and
> their life window in inactive list is too small to be useful.

This one of the reasons why we unconditionally deactivate
the active anon pages, and do background scanning of the
active anon list when reclaiming page cache pages.

We want to always move some pages to the inactive anon
list, so it does not get too small.

-- 
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