From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751850Ab1GaPSJ (ORCPT ); Sun, 31 Jul 2011 11:18:09 -0400 Received: from mail-pz0-f42.google.com ([209.85.210.42]:56355 "EHLO mail-pz0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751772Ab1GaPR7 (ORCPT ); Sun, 31 Jul 2011 11:17:59 -0400 Date: Mon, 1 Aug 2011 00:17:49 +0900 From: Minchan Kim To: Mel Gorman Cc: Linux-MM , LKML , XFS , Dave Chinner , Christoph Hellwig , Johannes Weiner , Wu Fengguang , Jan Kara , Rik van Riel Subject: Re: [PATCH 6/8] mm: vmscan: Throttle reclaim if encountering too many dirty pages under writeback Message-ID: <20110731151749.GD1735@barrios-desktop> References: <1311265730-5324-1-git-send-email-mgorman@suse.de> <1311265730-5324-7-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1311265730-5324-7-git-send-email-mgorman@suse.de> 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 21, 2011 at 05:28:48PM +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. > > Signed-off-by: Mel Gorman Reviewed-by: Minchan Kim -- Kind regards, Minchan Kim