From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753259Ab1GNGdh (ORCPT ); Thu, 14 Jul 2011 02:33:37 -0400 Received: from cantor2.suse.de ([195.135.220.15]:57787 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751048Ab1GNGdg (ORCPT ); Thu, 14 Jul 2011 02:33:36 -0400 Date: Thu, 14 Jul 2011 07:33:32 +0100 From: Mel Gorman To: Dave Chinner Cc: Linux-MM , LKML , XFS , Christoph Hellwig , Johannes Weiner , Wu Fengguang , Jan Kara , Rik van Riel , Minchan Kim Subject: Re: [PATCH 3/5] mm: vmscan: Throttle reclaim if encountering too many dirty pages under writeback Message-ID: <20110714063332.GP7529@suse.de> References: <1310567487-15367-1-git-send-email-mgorman@suse.de> <1310567487-15367-4-git-send-email-mgorman@suse.de> <20110713234150.GW23038@dastard> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20110713234150.GW23038@dastard> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 14, 2011 at 09:41:50AM +1000, Dave Chinner wrote: > On Wed, Jul 13, 2011 at 03:31:25PM +0100, Mel Gorman wrote: > > Workloads that are allocating frequently and writing files place a > > large number of dirty pages on the LRU. With use-once logic, it is > > possible for them to reach the end of the LRU quickly requiring the > > reclaimer to scan more to find clean pages. Ordinarily, processes that > > are dirtying memory will get throttled by dirty balancing but this > > is a global heuristic and does not take into account that LRUs are > > maintained on a per-zone basis. This can lead to a situation whereby > > reclaim is scanning heavily, skipping over a large number of pages > > under writeback and recycling them around the LRU consuming CPU. > > > > This patch checks how many of the number of pages isolated from the > > LRU were dirty. If a percentage of them are dirty, the process will be > > throttled if a blocking device is congested or the zone being scanned > > is marked congested. The percentage that must be dirty depends on > > the priority. At default priority, all of them must be dirty. At > > DEF_PRIORITY-1, 50% of them must be dirty, DEF_PRIORITY-2, 25% > > etc. i.e. as pressure increases the greater the likelihood the process > > will get throttled to allow the flusher threads to make some progress. > > It still doesn't take into account how many pages under writeback > were skipped. If there are lots of pages that are under writeback, I > think we still want to throttle to give IO a chance to complete and > clean those pages before scanning again.... > An earlier revision did take them into account but in these tests at least, 0 pages at the end of the LRU were PageWriteback. I expect this to change when multiple processes and CPUs were in use but am ignoring it for the moment. -- Mel Gorman SUSE Labs 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 p6E6XcgW121112 for ; Thu, 14 Jul 2011 01:33:38 -0500 Received: from mx2.suse.de (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 72984EC1E98 for ; Wed, 13 Jul 2011 23:33:36 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) by cuda.sgi.com with ESMTP id 50eG1B9azI5qJDTx for ; Wed, 13 Jul 2011 23:33:36 -0700 (PDT) Date: Thu, 14 Jul 2011 07:33:32 +0100 From: Mel Gorman Subject: Re: [PATCH 3/5] mm: vmscan: Throttle reclaim if encountering too many dirty pages under writeback Message-ID: <20110714063332.GP7529@suse.de> References: <1310567487-15367-1-git-send-email-mgorman@suse.de> <1310567487-15367-4-git-send-email-mgorman@suse.de> <20110713234150.GW23038@dastard> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20110713234150.GW23038@dastard> 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: Dave Chinner Cc: Rik van Riel , Jan Kara , LKML , XFS , Christoph Hellwig , Linux-MM , Minchan Kim , Wu Fengguang , Johannes Weiner On Thu, Jul 14, 2011 at 09:41:50AM +1000, Dave Chinner wrote: > On Wed, Jul 13, 2011 at 03:31:25PM +0100, Mel Gorman wrote: > > Workloads that are allocating frequently and writing files place a > > large number of dirty pages on the LRU. With use-once logic, it is > > possible for them to reach the end of the LRU quickly requiring the > > reclaimer to scan more to find clean pages. Ordinarily, processes that > > are dirtying memory will get throttled by dirty balancing but this > > is a global heuristic and does not take into account that LRUs are > > maintained on a per-zone basis. This can lead to a situation whereby > > reclaim is scanning heavily, skipping over a large number of pages > > under writeback and recycling them around the LRU consuming CPU. > > > > This patch checks how many of the number of pages isolated from the > > LRU were dirty. If a percentage of them are dirty, the process will be > > throttled if a blocking device is congested or the zone being scanned > > is marked congested. The percentage that must be dirty depends on > > the priority. At default priority, all of them must be dirty. At > > DEF_PRIORITY-1, 50% of them must be dirty, DEF_PRIORITY-2, 25% > > etc. i.e. as pressure increases the greater the likelihood the process > > will get throttled to allow the flusher threads to make some progress. > > It still doesn't take into account how many pages under writeback > were skipped. If there are lots of pages that are under writeback, I > think we still want to throttle to give IO a chance to complete and > clean those pages before scanning again.... > An earlier revision did take them into account but in these tests at least, 0 pages at the end of the LRU were PageWriteback. I expect this to change when multiple processes and CPUs were in use but am ignoring it for the moment. -- Mel Gorman SUSE Labs _______________________________________________ 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 mail6.bemta8.messagelabs.com (mail6.bemta8.messagelabs.com [216.82.243.55]) by kanga.kvack.org (Postfix) with ESMTP id AC53390011A for ; Thu, 14 Jul 2011 02:33:37 -0400 (EDT) Date: Thu, 14 Jul 2011 07:33:32 +0100 From: Mel Gorman Subject: Re: [PATCH 3/5] mm: vmscan: Throttle reclaim if encountering too many dirty pages under writeback Message-ID: <20110714063332.GP7529@suse.de> References: <1310567487-15367-1-git-send-email-mgorman@suse.de> <1310567487-15367-4-git-send-email-mgorman@suse.de> <20110713234150.GW23038@dastard> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20110713234150.GW23038@dastard> Sender: owner-linux-mm@kvack.org List-ID: To: Dave Chinner Cc: Linux-MM , LKML , XFS , Christoph Hellwig , Johannes Weiner , Wu Fengguang , Jan Kara , Rik van Riel , Minchan Kim On Thu, Jul 14, 2011 at 09:41:50AM +1000, Dave Chinner wrote: > On Wed, Jul 13, 2011 at 03:31:25PM +0100, Mel Gorman wrote: > > Workloads that are allocating frequently and writing files place a > > large number of dirty pages on the LRU. With use-once logic, it is > > possible for them to reach the end of the LRU quickly requiring the > > reclaimer to scan more to find clean pages. Ordinarily, processes that > > are dirtying memory will get throttled by dirty balancing but this > > is a global heuristic and does not take into account that LRUs are > > maintained on a per-zone basis. This can lead to a situation whereby > > reclaim is scanning heavily, skipping over a large number of pages > > under writeback and recycling them around the LRU consuming CPU. > > > > This patch checks how many of the number of pages isolated from the > > LRU were dirty. If a percentage of them are dirty, the process will be > > throttled if a blocking device is congested or the zone being scanned > > is marked congested. The percentage that must be dirty depends on > > the priority. At default priority, all of them must be dirty. At > > DEF_PRIORITY-1, 50% of them must be dirty, DEF_PRIORITY-2, 25% > > etc. i.e. as pressure increases the greater the likelihood the process > > will get throttled to allow the flusher threads to make some progress. > > It still doesn't take into account how many pages under writeback > were skipped. If there are lots of pages that are under writeback, I > think we still want to throttle to give IO a chance to complete and > clean those pages before scanning again.... > An earlier revision did take them into account but in these tests at least, 0 pages at the end of the LRU were PageWriteback. I expect this to change when multiple processes and CPUs were in use but am ignoring it for the moment. -- Mel Gorman SUSE Labs -- 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