From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rik van Riel Subject: Re: [PATCH 11/12] vmscan: Write out dirty pages in batch Date: Mon, 14 Jun 2010 17:13:37 -0400 Message-ID: <4C169B81.8010707@redhat.com> References: <1276514273-27693-1-git-send-email-mel@csn.ul.ie> <1276514273-27693-12-git-send-email-mel@csn.ul.ie> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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 To: Mel Gorman Return-path: In-Reply-To: <1276514273-27693-12-git-send-email-mel@csn.ul.ie> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org 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. > 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 :) > Signed-off-by: Mel Gorman Reviewed-by: Rik van Riel -- All rights reversed -- 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