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 p7C2lpOd019230 for ; Thu, 11 Aug 2011 21:47:51 -0500 Received: from mx1.redhat.com (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id BE3CB1BFFA1B for ; Thu, 11 Aug 2011 19:47:49 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by cuda.sgi.com with ESMTP id qH1z3SCIz4NJWHOr for ; Thu, 11 Aug 2011 19:47:49 -0700 (PDT) Message-ID: <4E449445.9000205@redhat.com> Date: Thu, 11 Aug 2011 22:47:33 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 6/7] mm: vmscan: Throttle reclaim if encountering too many dirty pages under writeback References: <1312973240-32576-1-git-send-email-mgorman@suse.de> <1312973240-32576-7-git-send-email-mgorman@suse.de> In-Reply-To: <1312973240-32576-7-git-send-email-mgorman@suse.de> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Mel Gorman Cc: Jan Kara , LKML , XFS , Christoph Hellwig , Linux-MM , Minchan Kim , Wu Fengguang , Johannes Weiner On 08/10/2011 06:47 AM, 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 and under writeback. If a percentage of them under > writeback, the process will be throttled if a backing device or the > zone is congested. Note that this applies whether it is anonymous or > file-backed pages that are under writeback meaning that swapping is > potentially throttled. This is intentional due to the fact if the > swap device is congested, scanning more pages and dispatching more > IO is not going to help matters. > > The percentage that must be in writeback depends on the priority. At > default priority, all of them must be dirty. At DEF_PRIORITY-1, 50% > of them must be, 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. > > Signed-off-by: Mel Gorman > Reviewed-by: Minchan Kim > Acked-by: Johannes Weiner Acked-by: Rik van Riel -- All rights reversed _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs