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 p93BMGHa237630 for ; Mon, 3 Oct 2011 06:22:16 -0500 Received: from mx2.suse.de (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id C4F1916B317D for ; Mon, 3 Oct 2011 04:28:43 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) by cuda.sgi.com with ESMTP id b6y7bLIt42vp7B4d for ; Mon, 03 Oct 2011 04:28:43 -0700 (PDT) Date: Mon, 3 Oct 2011 12:22:05 +0100 From: Mel Gorman Subject: Re: [patch 1/5] mm: exclude reserved pages from dirtyable memory Message-ID: <20111003112205.GA5011@suse.de> References: <1317367044-475-1-git-send-email-jweiner@redhat.com> <1317367044-475-2-git-send-email-jweiner@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1317367044-475-2-git-send-email-jweiner@redhat.com> 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: Johannes Weiner Cc: Rik van Riel , linux-ext4@vger.kernel.org, Jan Kara , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, xfs@oss.sgi.com, Christoph Hellwig , linux-mm@kvack.org, Andreas Dilger , Minchan Kim , Shaohua Li , linux-fsdevel@vger.kernel.org, Theodore Ts'o , Andrew Morton , Wu Fengguang , Chris Mason On Fri, Sep 30, 2011 at 09:17:20AM +0200, Johannes Weiner wrote: > The amount of dirtyable pages should not include the full number of > free pages: there is a number of reserved pages that the page > allocator and kswapd always try to keep free. > > The closer (reclaimable pages - dirty pages) is to the number of > reserved pages, the more likely it becomes for reclaim to run into > dirty pages: > > +----------+ --- > | anon | | > +----------+ | > | | | > | | -- dirty limit new -- flusher new > | file | | | > | | | | > | | -- dirty limit old -- flusher old > | | | > +----------+ --- reclaim > | reserved | > +----------+ > | kernel | > +----------+ > > This patch introduces a per-zone dirty reserve that takes both the > lowmem reserve as well as the high watermark of the zone into account, > and a global sum of those per-zone values that is subtracted from the > global amount of dirtyable pages. The lowmem reserve is unavailable > to page cache allocations and kswapd tries to keep the high watermark > free. We don't want to end up in a situation where reclaim has to > clean pages in order to balance zones. > > Not treating reserved pages as dirtyable on a global level is only a > conceptual fix. In reality, dirty pages are not distributed equally > across zones and reclaim runs into dirty pages on a regular basis. > > But it is important to get this right before tackling the problem on a > per-zone level, where the distance between reclaim and the dirty pages > is mostly much smaller in absolute numbers. > > Signed-off-by: Johannes Weiner > Reviewed-by: Rik van Riel Acked-by: Mel Gorman -- Mel Gorman SUSE Labs _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs