Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755231Ab2HGOwm (ORCPT ); Tue, 7 Aug 2012 10:52:42 -0400 Received: from cantor2.suse.de ([195.135.220.15]:60968 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755191Ab2HGOwk (ORCPT ); Tue, 7 Aug 2012 10:52:40 -0400 Date: Tue, 7 Aug 2012 15:52:33 +0100 From: Mel Gorman To: Rik van Riel Cc: Linux-MM , Minchan Kim , Jim Schutt , LKML Subject: Re: [PATCH 6/6] mm: have order > 0 compaction start near a pageblock with free pages Message-ID: <20120807145233.GG29814@suse.de> References: <1344342677-5845-1-git-send-email-mgorman@suse.de> <1344342677-5845-7-git-send-email-mgorman@suse.de> <50212A05.2070503@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <50212A05.2070503@redhat.com> 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 Content-Length: 1502 Lines: 44 On Tue, Aug 07, 2012 at 10:45:25AM -0400, Rik van Riel wrote: > On 08/07/2012 08:31 AM, Mel Gorman wrote: > >commit [7db8889a: mm: have order> 0 compaction start off where it left] > >introduced a caching mechanism to reduce the amount work the free page > >scanner does in compaction. However, it has a problem. Consider two process > >simultaneously scanning free pages > > > > C > >Process A M S F > > |---------------------------------------| > >Process B M FS > > Argh. Good spotting. > > >This is not optimal and it can still race but the compact_cached_free_pfn > >will be pointing to or very near a pageblock with free pages. > > Agreed on the "not optimal", but I also cannot think of a better > idea right now. Getting this fixed for 3.6 is important, we can > think of future optimizations in San Diego. > Sounds like a plan. > >Signed-off-by: Mel Gorman > > Reviewed-by: Rik van Riel > Thanks very much. Jim, what are the chances of getting this series tested with your large data workload? As it's on top of 3.5, it should be less scary than testing 3.6-rc1 but if you are comfortable testing 3.6-rc1 then please test with just this patch on top. -- 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/