From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760908AbYAHLkV (ORCPT ); Tue, 8 Jan 2008 06:40:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760211AbYAHLiW (ORCPT ); Tue, 8 Jan 2008 06:38:22 -0500 Received: from smtp2.linux-foundation.org ([207.189.120.14]:37273 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760204AbYAHLiV (ORCPT ); Tue, 8 Jan 2008 06:38:21 -0500 Date: Tue, 8 Jan 2008 03:38:01 -0800 From: Andrew Morton To: Mike Galbraith Cc: LKML Subject: Re: [vm] writing to UDF DVD+RW (/dev/sr0) while under memory pressure: box ==> doorstop Message-Id: <20080108033801.40d0043a.akpm@linux-foundation.org> In-Reply-To: <1199790316.4094.57.camel@homer.simson.net> References: <1199447212.4529.13.camel@homer.simson.net> <1199612533.4384.54.camel@homer.simson.net> <1199642470.3927.12.camel@homer.simson.net> <20080106122954.d8f04c98.akpm@linux-foundation.org> <1199790316.4094.57.camel@homer.simson.net> X-Mailer: Sylpheed 2.4.1 (GTK+ 2.8.17; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 08 Jan 2008 12:05:16 +0100 Mike Galbraith wrote: > > On Sun, 2008-01-06 at 12:29 -0800, Andrew Morton wrote: > > On Sun, 06 Jan 2008 19:01:10 +0100 Mike Galbraith wrote: > > > > > > > > On Sun, 2008-01-06 at 10:42 +0100, Mike Galbraith wrote: > > > > FWIW, here's box having same seizure writing to /dev/pktcdvd/sr0. > > > > > > Ugh, horrid device IO ==> horrid VM AFIKT. I'll continue rummaging, but > > > I wonder, am I doing something _so_ stupid as to warrant zero response? > > > > > > > Copying linux-mm might have helped. Bad time of year, too. > > > > >From the traces it looks like all IO has stopped and everyone is waiting > > (directly or indirectly) for certain IO completions. Is that really true, > > or is IO still dribbling along? > > > > >From the kswapd0 trace it would appear that UDF is doing synchronous writes > > (udf_update_inode->sync_dirty_buffer) which perhaps is making things > > mightily slow. > > This is a pretty uninteresting thread except for the VM aspect, but > rather than leave it dangling, I'll laugh at my naivety and close. > > Seeks on DVD drives are apparently far FAR more horrible that I ever > imagined, so writing to a filesystem on a DVD+RW in effect constitutes > the stupid thing I was worried about above. Make an image, populate it, > write it instead... sure to be a truckload faster, and due to the VM > connection, much safer too. Oh well. > Well. From your earlier trace it appeared that something was causing the filesystem to perform synchronous inode writes - sync_dirty_buffer() was called. This will cause many more seeks than would occur if we were doing full delayed writing, with obvious throughput implications.