From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id p72BLr5E099543 for ; Tue, 2 Aug 2011 06:21:54 -0500 Received: from mx2.suse.de (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id B46FD12F4167 for ; Tue, 2 Aug 2011 04:22:35 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) by cuda.sgi.com with ESMTP id KxdEkbWo7vt4eC0J for ; Tue, 02 Aug 2011 04:22:35 -0700 (PDT) Date: Tue, 2 Aug 2011 12:21:46 +0100 From: Mel Gorman Subject: Re: [PATCH 1/8] mm: vmscan: Do not writeback filesystem pages in direct reclaim Message-ID: <20110802112146.GD10436@suse.de> References: <1311265730-5324-1-git-send-email-mgorman@suse.de> <1311265730-5324-2-git-send-email-mgorman@suse.de> <20110731150606.GB1735@barrios-desktop> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20110731150606.GB1735@barrios-desktop> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Minchan Kim Cc: Rik van Riel , Jan Kara , LKML , XFS , Christoph Hellwig , Linux-MM , Wu Fengguang , Johannes Weiner On Mon, Aug 01, 2011 at 12:06:06AM +0900, Minchan Kim wrote: > On Thu, Jul 21, 2011 at 05:28:43PM +0100, Mel Gorman wrote: > > From: Mel Gorman > > > > When kswapd is failing to keep zones above the min watermark, a process > > will enter direct reclaim in the same manner kswapd does. If a dirty > > page is encountered during the scan, this page is written to backing > > storage using mapping->writepage. > > > > This causes two problems. First, it can result in very deep call > > stacks, particularly if the target storage or filesystem are complex. > > Some filesystems ignore write requests from direct reclaim as a result. > > The second is that a single-page flush is inefficient in terms of IO. > > While there is an expectation that the elevator will merge requests, > > this does not always happen. Quoting Christoph Hellwig; > > > > The elevator has a relatively small window it can operate on, > > and can never fix up a bad large scale writeback pattern. > > > > This patch prevents direct reclaim writing back filesystem pages by > > checking if current is kswapd. Anonymous pages are still written to > > swap as there is not the equivalent of a flusher thread for anonymous > > pages. If the dirty pages cannot be written back, they are placed > > back on the LRU lists. There is now a direct dependency on dirty page > > balancing to prevent too many pages in the system being dirtied which > > would prevent reclaim making forward progress. > > > > Signed-off-by: Mel Gorman > Reviewed-by: Minchan Kim > Thanks > Nitpick. > We can change description of should_reclaim_stall. > > "Returns true if the caller should wait to clean dirty/writeback pages" > -> > "Returns true if direct reclaimer should wait to clean writeback pages" > Not a nitpick. At least one check for RECLAIM_MODE_SYNC is no longer reachable. I've added a new patch that updates the comment and has synchronous direct reclaim wait on pages under writeback. -- Mel Gorman SUSE Labs _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs