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

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Date:	Fri, 7 Aug 2009 13:24:34 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Rik van Riel <riel@...hat.com>, Avi Kivity <avi@...hat.com>,
	Wu Fengguang <fengguang.wu@...el.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>,
	Mel Gorman <mel@....ul.ie>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [RFC] respect the referenced bit of KVM guest pages?

On Fri, Aug 7, 2009 at 8:41 AM, KOSAKI
Motohiro<kosaki.motohiro@...fujitsu.com> wrote:
> (cc to memcg folks)
>
>> Avi Kivity wrote:
>> > On 08/06/2009 01:59 PM, Wu Fengguang wrote:
>>
>> >> As a refinement, the static variable 'recent_all_referenced' could be
>> >> moved to struct zone or made a per-cpu variable.
>> >
>> > Definitely this should be made part of the zone structure, consider the
>> > original report where the problem occurs in a 128MB zone (where we can
>> > expect many pages to have their referenced bit set).
>>
>> The problem did not occur in a 128MB zone, but in a 128MB cgroup.
>>
>> Putting it in the zone means that the cgroup, which may have
>> different behaviour from the rest of the zone, due to excessive
>> memory pressure inside the cgroup, does not get the right
>> statistics.
>
> maybe, I heven't catch your point.
>
> Current memcgroup logic also use recent_scan/recent_rotate statistics.
> Isn't it enought?

I don't understand the context, I'll look at the problem when I am
back (I am away from work for the next few days).

Balbir
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