Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932476AbaDHOrm (ORCPT ); Tue, 8 Apr 2014 10:47:42 -0400 Received: from cantor2.suse.de ([195.135.220.15]:35234 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932294AbaDHOrk (ORCPT ); Tue, 8 Apr 2014 10:47:40 -0400 Date: Tue, 8 Apr 2014 15:47:35 +0100 From: Mel Gorman To: Christoph Lameter Cc: sivanich@sgi.com, Andrew Morton , Robert Haas , Josh Berkus , Andres Freund , Linux-MM , LKML Subject: Re: [PATCH 1/2] mm: Disable zone_reclaim_mode by default Message-ID: <20140408144735.GK7292@suse.de> References: <1396910068-11637-1-git-send-email-mgorman@suse.de> <1396910068-11637-2-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 08, 2014 at 09:14:05AM -0500, Christoph Lameter wrote: > On Mon, 7 Apr 2014, Mel Gorman wrote: > > > zone_reclaim_mode causes processes to prefer reclaiming memory from local > > node instead of spilling over to other nodes. This made sense initially when > > NUMA machines were almost exclusively HPC and the workload was partitioned > > into nodes. The NUMA penalties were sufficiently high to justify reclaiming > > the memory. On current machines and workloads it is often the case that > > zone_reclaim_mode destroys performance but not all users know how to detect > > this. Favour the common case and disable it by default. Users that are > > sophisticated enough to know they need zone_reclaim_mode will detect it. > > Ok that is going to require SGI machines to deal with zone_reclaim > configurations on bootup. Dimitri? Any comments? > The SGI machines are also likely to be managed by system administrators who are both aware of zone_reclaim_mode and know how to evaluate if it should be enabled or not. The pair of patches is really aimmed at the common case of 2-8 socket machines running workloads that are not NUMA aware. -- Mel Gorman SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/