From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id E1F9D6B005C for ; Sun, 17 May 2009 23:49:02 -0400 (EDT) Date: Mon, 18 May 2009 11:49:07 +0800 From: Wu Fengguang Subject: Re: [PATCH 4/4] zone_reclaim_mode is always 0 by default Message-ID: <20090518034907.GF5869@localhost> References: <20090513120155.5879.A69D9226@jp.fujitsu.com> <20090513120729.5885.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090513120729.5885.A69D9226@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: LKML , linux-mm , Andrew Morton , Rik van Riel , Christoph Lameter , "Zhang, Yanmin" List-ID: On Wed, May 13, 2009 at 12:08:12PM +0900, 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. I can confirm this, Yanmin recently ran into exactly such a regression, which was fixed by manually disabling the zone reclaim mode. So I guess you can safely add an Tested-by: "Zhang, Yanmin" > Thus, zone_reclaim == 0 is better by default. sorry, HPC gusy. > you need to turn zone_reclaim_mode on manually now. I guess the borderline will continue to blur up. It will be more dependent on workloads instead of physical NUMA capabilities. So Acked-by: Wu Fengguang > Signed-off-by: KOSAKI Motohiro > Cc: Christoph Lameter > Cc: Rik van Riel > --- > mm/page_alloc.c | 7 ------- > 1 file changed, 7 deletions(-) > > Index: b/mm/page_alloc.c > =================================================================== > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2494,13 +2494,6 @@ static void build_zonelists(pg_data_t *p > int distance = node_distance(local_node, node); > > /* > - * If another node is sufficiently far away then it is better > - * to reclaim pages in a zone before going off node. > - */ > - if (distance > RECLAIM_DISTANCE) > - zone_reclaim_mode = 1; > - > - /* > * We don't want to pressure a particular node. > * So adding penalty to the first node in same > * distance group to make it round-robin. > > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org