From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964776AbXBNVoe (ORCPT ); Wed, 14 Feb 2007 16:44:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964783AbXBNVoe (ORCPT ); Wed, 14 Feb 2007 16:44:34 -0500 Received: from smtp.osdl.org ([65.172.181.24]:47388 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964776AbXBNVo2 (ORCPT ); Wed, 14 Feb 2007 16:44:28 -0500 Date: Wed, 14 Feb 2007 13:44:08 -0800 From: Andrew Morton To: Nick Piggin Cc: NeilBrown , nfs@lists.sourceforge.net, linux-kernel@vger.kernel.org, Norman Weathers , "Vladimir V \".\" Saveliev" Subject: Re: [PATCH] knfsd: Stop NFSD writes from being broken into lots of little writes to filesystem. Message-Id: <20070214134408.431cddcc.akpm@linux-foundation.org> In-Reply-To: <45D15687.5080505@yahoo.com.au> References: <20070213170049.3488.patches@notabene> <1070213060131.3560@suse.de> <45D15687.5080505@yahoo.com.au> X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.6; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 13 Feb 2007 17:11:19 +1100 Nick Piggin wrote: > NeilBrown wrote: > > Another nfsd patch for 2.6.21... > > > > ### Comments for Changeset > > > > When NFSD receives a write request, the data is typically in a number > > of 1448 byte segments and writev is used to collect them together. > > > > Unfortunately, generic_file_buffered_write passes these to the filesystem > > one at a time, so an e.g. 32K over-write becomes a series of partial-page > > writes to each page, causing the filesystem to have to pre-read those > > pages - wasted effort. > > > > generic_file_buffered_write handles one segment of the vector at a > > time as it has to pre-fault in each segment to avoid deadlocks. When > > writing from kernel-space (and nfsd does) this is not an issue, so > > generic_file_buffered_write does not need to break and iovec from nfsd > > into little pieces. > > > > This patch avoids the splitting when get_fs is KERNEL_DS as it is > > from NFSd. > > > > This issue was introduced by commit 6527c2bdf1f833cc18e8f42bd97973d583e4aa83 > > > > Cc: Nick Piggin > > FWIW, you can put Acked-by: me there if you'd like. > It's yet another patch we need to revert if/when we get the write()-deadlock stuff sorted out. So please add negative-this to that patch series.