linux-kernel - Re: [RFC] respect the referenced bit of KVM guest pages?

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Message-ID: <20090816055957.GS5087@balbir.in.ibm.com>
Date:	Sun, 16 Aug 2009 11:29:57 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Rik van Riel <riel@...hat.com>, Avi Kivity <avi@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	"Dike, Jeffrey G" <jeffrey.g.dike@...el.com>,
	"Yu, Wilfred" <wilfred.yu@...el.com>,
	"Kleen, Andi" <andi.kleen@...el.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mel@....ul.ie>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [RFC] respect the referenced bit of KVM guest pages?

* Wu Fengguang <fengguang.wu@...el.com> [2009-08-16 12:55:22]:

> On Sun, Aug 16, 2009 at 11:56:39AM +0800, Rik van Riel wrote:
> > Wu Fengguang wrote:
> > 
> > > Right, but I meant busty page allocations and accesses on them, which
> > > can make a large continuous segment of referenced pages in LRU list,
> > > say 50MB.  They may or may not be valuable as a whole, however a local
> > > algorithm may keep the first 4MB and drop the remaining 46MB.
> > 
> > I wonder if the problem is that we simply do not keep a large
> > enough inactive list in Jeff's test.  If we do not, pages do
> > not have a chance to be referenced again before the reclaim
> > code comes in.
> 
> Exactly, that's the case I call the list FIFO.
> 
> > The cgroup stats should show how many active anon and inactive
> > anon pages there are in the cgroup.
> 
> Jeff, can you have a look at these stats? Thanks!

Another experiment would be to toy with memory.swappiness (although
defaults should work well). Could you compare the in-guest values of
nr_*active* with the cgroup values as seen by the host?

-- 
	Balbir
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