From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754343Ab0GZKwS (ORCPT ); Mon, 26 Jul 2010 06:52:18 -0400 Received: from gir.skynet.ie ([193.1.99.77]:42169 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753991Ab0GZKwQ (ORCPT ); Mon, 26 Jul 2010 06:52:16 -0400 Date: Mon, 26 Jul 2010 11:52:00 +0100 From: Mel Gorman To: Wu Fengguang Cc: Andrew Morton , Dave Chinner , Jan Kara , Christoph Hellwig , Chris Mason , Jens Axboe , LKML , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 2/6] writeback: the kupdate expire timestamp should be a moving target Message-ID: <20100726105200.GK5300@csn.ul.ie> References: <20100722050928.653312535@intel.com> <20100722061822.630779474@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20100722061822.630779474@intel.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 On Thu, Jul 22, 2010 at 01:09:30PM +0800, Wu Fengguang wrote: > Dynamicly compute the dirty expire timestamp at queue_io() time. > Also remove writeback_control.older_than_this which is no longer used. > > writeback_control.older_than_this used to be determined at entrance to > the kupdate writeback work. This _static_ timestamp may go stale if the > kupdate work runs on and on. The flusher may then stuck with some old > busy inodes, never considering newly expired inodes thereafter. > > This has two possible problems: > > - It is unfair for a large dirty inode to delay (for a long time) the > writeback of small dirty inodes. > > - As time goes by, the large and busy dirty inode may contain only > _freshly_ dirtied pages. Ignoring newly expired dirty inodes risks > delaying the expired dirty pages to the end of LRU lists, triggering > the very bad pageout(). Neverthless this patch merely addresses part > of the problem. > > CC: Jan Kara > Signed-off-by: Wu Fengguang Again, makes sense and I can't see a problem. There are some worth smithing issues in the changelog such as Dynamicly -> Dynamically and s/writeback_control.older_than_this used/writeback_control.older_than_this is used/ but other than that. Acked-by: Mel Gorman -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab