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 3DC9D6B004D for ; Tue, 9 Jun 2009 07:26:55 -0400 (EDT) Date: Tue, 9 Jun 2009 07:02:14 -0500 From: Robin Holt Subject: Re: [PATCH v4] zone_reclaim is always 0 by default Message-ID: <20090609120213.GA18753@attica.americas.sgi.com> References: <20090604192236.9761.A69D9226@jp.fujitsu.com> <20090608115048.GA15070@csn.ul.ie> <20090609095507.GA9851@attica.americas.sgi.com> <20090609103754.GN18380@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090609103754.GN18380@csn.ul.ie> Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Robin Holt , KOSAKI Motohiro , Christoph Lameter , Rik van Riel , "Zhang, Yanmin" , Wu Fengguang , linux-ia64@vger.kernel.org, linuxppc-dev@ozlabs.org, LKML , linux-mm , Andrew Morton List-ID: On Tue, Jun 09, 2009 at 11:37:55AM +0100, Mel Gorman wrote: > On Tue, Jun 09, 2009 at 04:55:07AM -0500, Robin Holt wrote: > > On Mon, Jun 08, 2009 at 12:50:48PM +0100, Mel Gorman wrote: > > > > Let me start by saying I agree completely with everything you wrote and > > still disagree with this patch, but was willing to compromise and work > > around this for our upcoming x86_64 machine by putting a "value add" > > into our packaging of adding a sysctl that turns reclaim back on. > > > > To be honest, I'm more leaning towards a NACK than an ACK on this one. I > don't support enough NUMA machines to feel strongly enough about it but > unconditionally setting zone_reclaim_mode to 0 on x86-64 just because i7's > might be there seems ill-advised to me and will have other consequences for > existing more traditional x86-64 NUMA machines. I was sort-of planning on coming up with an x86_64 arch specific function for setting zone_reclaim_mode, but didn't like the direction things were going. Something to the effect of... --- 20090609.orig/mm/page_alloc.c 2009-06-09 06:51:34.000000000 -0500 +++ 20090609/mm/page_alloc.c 2009-06-09 06:55:00.160762069 -0500 @@ -2326,12 +2326,7 @@ static void build_zonelists(pg_data_t *p while ((node = find_next_best_node(local_node, &used_mask)) >= 0) { 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; + zone_reclaim_mode = arch_zone_reclaim_mode(distance); /* * We don't want to pressure a particular node. And then letting each arch define an arch_zone_reclaim_mode(). If other values are needed in the determination, we would add parameters to reflect this. For ia64, add static inline ia64_zone_reclaim_mode(int distance) { if (distance > 15) return 1; } #define arch_zone_reclaim_mode(_d) ia64_zone_reclaim_mode(_d) Then, inside x86_64_zone_reclaim_mode(), I could make it something like if (distance > 40 || is_uv_system()) return 1; In the end, I didn't think this fight was worth fighting given how ugly this felt. Upon second thought, I am beginning to think it is not that bad, but I also don't think it is that good either. Thanks, 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