From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756960AbYIOXVS (ORCPT ); Mon, 15 Sep 2008 19:21:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753352AbYIOXVE (ORCPT ); Mon, 15 Sep 2008 19:21:04 -0400 Received: from gir.skynet.ie ([193.1.99.77]:44188 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751945AbYIOXVD (ORCPT ); Mon, 15 Sep 2008 19:21:03 -0400 Date: Tue, 16 Sep 2008 00:20:57 +0100 From: Mel Gorman To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kamezawa.hiroyu@jp.fujitsu.com, apw@shadowen.org Subject: Re: [PATCH] Mark the correct zone as full when scanning zonelists Message-ID: <20080915232056.GA23031@csn.ul.ie> References: <20080911212550.GA18087@csn.ul.ie> <20080911144155.c70ef145.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20080911144155.c70ef145.akpm@linux-foundation.org> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (11/09/08 14:41), Andrew Morton didst pronounce: > On Thu, 11 Sep 2008 22:25:51 +0100 > Mel Gorman wrote: > > > The for_each_zone_zonelist() uses a struct zoneref *z cursor when scanning > > zonelists to keep track of where in the zonelist it is. The zoneref that > > is returned corresponds to the the next zone that is to be scanned, not > > the current one as it originally thought of as an opaque list. > > > > When the page allocator is scanning a zonelist, it marks zones that it > > temporarily full zones to eliminate near-future scanning attempts. > > That sentence needs help. > > > It uses > > the zoneref for the marking and consequently the incorrect zone gets marked > > full. This leads to a suitable zone being skipped in the mistaken belief > > it is full. This patch corrects the problem by changing zoneref to be the > > current zone being scanned instead of the next one. > > Applicable to 2.6.26 as well, yes? > > > Someone reported a bug a few weeks ago which I think this patch will fix, > yes? I don't remember who that was, nor do I recall the precise details > of what the userspace-visible (mis)behaviour was. > > Are you able to fill in the gaps here? I searched through the archives and couldn't find a bug report that this patch may be the fix to. However, I understand that the initial leader could have been a lot better. > Put yourself in the position of > a poor little -stable maintainer scratching his head wondering ytf he > was sent this patch. > > Thanks. > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab