From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752974Ab1GMXfA (ORCPT ); Wed, 13 Jul 2011 19:35:00 -0400 Received: from ipmail07.adl2.internode.on.net ([150.101.137.131]:16497 "EHLO ipmail07.adl2.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752946Ab1GMXe7 (ORCPT ); Wed, 13 Jul 2011 19:34:59 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AqYCAJsqHk55LCkBgWdsb2JhbABTp0EVAQEWJiXLQg6GLASjQw Date: Thu, 14 Jul 2011 09:34:49 +1000 From: Dave Chinner To: Mel Gorman Cc: Linux-MM , LKML , XFS , Christoph Hellwig , Johannes Weiner , Wu Fengguang , Jan Kara , Rik van Riel , Minchan Kim Subject: Re: [PATCH 1/5] mm: vmscan: Do not writeback filesystem pages in direct reclaim Message-ID: <20110713233449.GU23038@dastard> References: <1310567487-15367-1-git-send-email-mgorman@suse.de> <1310567487-15367-2-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1310567487-15367-2-git-send-email-mgorman@suse.de> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 13, 2011 at 03:31:23PM +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 anonymos > pages. If the dirty pages cannot be written back, they are placed > back on the LRU lists. > > Signed-off-by: Mel Gorman Ok, so that makes the .writepage checks in ext4, xfs and btrfs for this condition redundant. In effect the patch should be a no-op for those filesystems. Can you also remove the checks in the filesystems? Cheers, Dave. -- Dave Chinner david@fromorbit.com From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id p6DNZ03G105250 for ; Wed, 13 Jul 2011 18:35:00 -0500 Received: from ipmail07.adl2.internode.on.net (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 8BB811D854FF for ; Wed, 13 Jul 2011 16:34:58 -0700 (PDT) Received: from ipmail07.adl2.internode.on.net (ipmail07.adl2.internode.on.net [150.101.137.131]) by cuda.sgi.com with ESMTP id jvt0lQJz7ZSZGJSj for ; Wed, 13 Jul 2011 16:34:58 -0700 (PDT) Date: Thu, 14 Jul 2011 09:34:49 +1000 From: Dave Chinner Subject: Re: [PATCH 1/5] mm: vmscan: Do not writeback filesystem pages in direct reclaim Message-ID: <20110713233449.GU23038@dastard> References: <1310567487-15367-1-git-send-email-mgorman@suse.de> <1310567487-15367-2-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1310567487-15367-2-git-send-email-mgorman@suse.de> 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: Mel Gorman Cc: Rik van Riel , Jan Kara , LKML , XFS , Christoph Hellwig , Linux-MM , Minchan Kim , Wu Fengguang , Johannes Weiner On Wed, Jul 13, 2011 at 03:31:23PM +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 anonymos > pages. If the dirty pages cannot be written back, they are placed > back on the LRU lists. > > Signed-off-by: Mel Gorman Ok, so that makes the .writepage checks in ext4, xfs and btrfs for this condition redundant. In effect the patch should be a no-op for those filesystems. Can you also remove the checks in the filesystems? Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 1FA116B004A for ; Wed, 13 Jul 2011 19:34:59 -0400 (EDT) Date: Thu, 14 Jul 2011 09:34:49 +1000 From: Dave Chinner Subject: Re: [PATCH 1/5] mm: vmscan: Do not writeback filesystem pages in direct reclaim Message-ID: <20110713233449.GU23038@dastard> References: <1310567487-15367-1-git-send-email-mgorman@suse.de> <1310567487-15367-2-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1310567487-15367-2-git-send-email-mgorman@suse.de> Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Linux-MM , LKML , XFS , Christoph Hellwig , Johannes Weiner , Wu Fengguang , Jan Kara , Rik van Riel , Minchan Kim On Wed, Jul 13, 2011 at 03:31:23PM +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 anonymos > pages. If the dirty pages cannot be written back, they are placed > back on the LRU lists. > > Signed-off-by: Mel Gorman Ok, so that makes the .writepage checks in ext4, xfs and btrfs for this condition redundant. In effect the patch should be a no-op for those filesystems. Can you also remove the checks in the filesystems? Cheers, Dave. -- Dave Chinner david@fromorbit.com -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org