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Message-ID: <4A0ADD88.9080705@redhat.com>
Date: Wed, 13 May 2009 10:47:36 -0400
From: Rik van Riel <riel@...hat.com>
To: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
CC: LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Christoph Lameter <cl@...ux-foundation.org>
Subject: Re: [PATCH 4/4] zone_reclaim_mode is always 0 by default
KOSAKI Motohiro wrote:
> Subject: [PATCH] zone_reclaim_mode is always 0 by default
>
> Current linux policy is, if the machine has large remote node distance,
> zone_reclaim_mode is enabled by default because we've be able to assume to
> large distance mean large server until recently.
>
> Unfrotunately, recent modern x86 CPU (e.g. Core i7, Opeteron) have P2P transport
> memory controller. IOW it's NUMA from software view.
>
> Some Core i7 machine has large remote node distance and zone_reclaim don't
> fit desktop and small file server. it cause performance degression.
>
> Thus, zone_reclaim == 0 is better by default. sorry, HPC gusy.
> you need to turn zone_reclaim_mode on manually now.
I'll believe that it causes a performance regression with the
old zone_reclaim behaviour, however the way you tweaked
zone_reclaim should make it behave a lot better, no?
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