From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: Re: NFS page states & writeback Date: Fri, 25 Mar 2011 22:32:29 +0800 Message-ID: <20110325143229.GA12875@localhost> References: <20110325012803.GA25052@quack.suse.cz> <20110325070054.GA5970@localhost> <20110325093957.GL26611@dastard> <20110325142253.GA11589@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , "linux-fsdevel@vger.kernel.org" , "linux-nfs@vger.kernel.org" , Andrew Morton , Christoph Hellwig To: Dave Chinner Return-path: Received: from mga01.intel.com ([192.55.52.88]:55168 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753770Ab1CYOcc (ORCPT ); Fri, 25 Mar 2011 10:32:32 -0400 Content-Disposition: inline In-Reply-To: <20110325142253.GA11589@localhost> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: > However there is another problem. Look at the below graph. Even though > the commits are sent to NFS server in relatively small size and evenly > distributed in time (the green points), the commit COMPLETION events > from the server are observed to be pretty bumpy over time (the blue > points sitting on the red lines). This may not be easily fixable.. So > we still have to live with bumpy NFS commit completions... > > http://www.kernel.org/pub/linux/kernel/people/wfg/writeback/dirty-throttling-v6/NFS/nfs-1dd-1M-8p-2945M-20%25-2.6.38-rc6-dt6+-2011-02-22-21-09/nfs-commit.png The bumpy commit completions result in large fluctuations in estimated write bandwidth (the red line): http://www.kernel.org/pub/linux/kernel/people/wfg/writeback/dirty-throttling-v6/NFS/nfs-1dd-1M-8p-2945M-20%25-2.6.38-rc6-dt6+-2011-02-22-21-09/balance_dirty_pages-bandwidth.png and fluctuated number of dirty pages (the red line): http://www.kernel.org/pub/linux/kernel/people/wfg/writeback/dirty-throttling-v6/NFS/nfs-1dd-1M-8p-2945M-20%25-2.6.38-rc6-dt6+-2011-02-22-21-09/balance_dirty_pages-pages.png And you can see the v6 patches still manages to keep the pause times (the red points) under 100ms (hands down!): http://www.kernel.org/pub/linux/kernel/people/wfg/writeback/dirty-throttling-v6/NFS/nfs-1dd-1M-8p-2945M-20%25-2.6.38-rc6-dt6+-2011-02-22-21-09/balance_dirty_pages-pause.png Thanks, Fengguang