Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757238Ab0FOKTT (ORCPT ); Tue, 15 Jun 2010 06:19:19 -0400 Received: from gir.skynet.ie ([193.1.99.77]:53258 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757190Ab0FOKTQ (ORCPT ); Tue, 15 Jun 2010 06:19:16 -0400 Date: Tue, 15 Jun 2010 11:18:58 +0100 From: Mel Gorman To: Rik van Riel Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Dave Chinner , Chris Mason , Nick Piggin , Johannes Weiner , Christoph Hellwig , KAMEZAWA Hiroyuki , Andrew Morton Subject: Re: [PATCH 11/12] vmscan: Write out dirty pages in batch Message-ID: <20100615101857.GB26788@csn.ul.ie> References: <1276514273-27693-1-git-send-email-mel@csn.ul.ie> <1276514273-27693-12-git-send-email-mel@csn.ul.ie> <4C169B81.8010707@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <4C169B81.8010707@redhat.com> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1737 Lines: 44 On Mon, Jun 14, 2010 at 05:13:37PM -0400, Rik van Riel wrote: > On 06/14/2010 07:17 AM, Mel Gorman wrote: >> Page reclaim cleans individual pages using a_ops->writepage() because from >> the VM perspective, it is known that pages in a particular zone must be freed >> soon, it considers the target page to be the oldest and it does not want >> to wait while background flushers cleans other pages. From a filesystem >> perspective this is extremely inefficient as it generates a very seeky >> IO pattern leading to the perverse situation where it can take longer to >> clean all dirty pages than it would have otherwise. > > Reclaiming clean pages should be fast enough that this should > make little, if any, difference. > Indeed, this was a bit weak. The original point of the patch was to write contiguous pages belonging to the same inode when they were encountered in that batch which made a bit more sense but didn't work out at first pass. >> This patch queues all dirty pages at once to maximise the chances that >> the write requests get merged efficiently. It also makes the next patch >> that avoids writeout from direct reclaim more straight-forward. > > However, this is a convincing argument :) > Thanks. >> Signed-off-by: Mel Gorman > > Reviewed-by: Rik van Riel > Thanks again :) -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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/