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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: Default zone_reclaim_mode = 1 on NUMA kernel is bad for file/email/web servers
Cc: kosaki.motohiro@jp.fujitsu.com, robm@fastmail.fm,
        linux-kernel@vger.kernel.org, "Bron Gondwana" <brong@fastmail.fm>,
        linux-mm <linux-mm@kvack.org>,
        Christoph Lameter <cl@linux-foundation.org>,
        Mel Gorman <mel@csn.ul.ie>
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Date: Mon, 27 Sep 2010 11:04:54 +0900 (JST)
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> On Thu, 16 Sep 2010 19:01:32 +0900 (JST)
> KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
> 
> > Yes, sadly intel motherboard turn on zone_reclaim_mode by default. and
> > current zone_reclaim_mode doesn't fit file/web server usecase ;-)
> > 
> > So, I've created new proof concept patch. This doesn't disable zone_reclaim
> > at all. Instead, distinguish for file cache and for anon allocation and
> > only file cache doesn't use zone-reclaim.
> > 
> > That said, high-end hpc user often turn on cpuset.memory_spread_page and
> > they avoid this issue. But, why don't we consider avoid it by default?
> > 
> > 
> > Rob, I wonder if following patch help you. Could you please try it?
> > 
> > 
> > Subject: [RFC] vmscan: file cache doesn't use zone_reclaim by default
> > 
> 
> Hm, can't we use migration of file caches rather than pageout in
> zone_reclaim_mode ? Doent' it fix anything ?

Doesn't.

Two problem. 1) Migration makes copy. then it's slower than zone_reclaim=0
2) Migration is only effective if target node has much free pages. but it
is not generic assumption.

For this case, zone_reclaim_mode=0 is best. my patch works as second best.
your one works as third.

If you have more concern, please let us know it.