LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Andrew Morton <akpm@linux-foundation.org>
To: Mike Galbraith <efault@gmx.de>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: Re: [vm] writing to UDF DVD+RW (/dev/sr0) while under memory pressure: box ==> doorstop
Date: Tue, 8 Jan 2008 03:38:01 -0800	[thread overview]
Message-ID: <20080108033801.40d0043a.akpm@linux-foundation.org> (raw)
In-Reply-To: <1199790316.4094.57.camel@homer.simson.net>

On Tue, 08 Jan 2008 12:05:16 +0100 Mike Galbraith <efault@gmx.de> wrote:

> 
> On Sun, 2008-01-06 at 12:29 -0800, Andrew Morton wrote:
> > On Sun, 06 Jan 2008 19:01:10 +0100 Mike Galbraith <efault@gmx.de> 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.


  reply	other threads:[~2008-01-08 11:40 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-04 11:46 Mike Galbraith
2008-01-06  9:42 ` Mike Galbraith
2008-01-06 18:01   ` Mike Galbraith
2008-01-06 20:29     ` Andrew Morton
2008-01-07  5:33       ` Mike Galbraith
2008-01-07  5:55         ` Mike Galbraith
2008-01-08 11:05       ` Mike Galbraith
2008-01-08 11:38         ` Andrew Morton [this message]
2008-01-08 15:21           ` Mike Galbraith
2008-01-08 15:27             ` Mike Galbraith
2008-01-09 11:11               ` Mike Galbraith
2008-01-09 23:01                 ` Andrew Morton
2008-01-10  4:21                   ` Mike Galbraith
2008-01-10 14:41                   ` Jan Kara
2008-01-10 15:29                     ` Mike Galbraith
2008-01-10 17:16                       ` Jan Kara

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20080108033801.40d0043a.akpm@linux-foundation.org \
    --to=akpm@linux-foundation.org \
    --cc=efault@gmx.de \
    --cc=linux-kernel@vger.kernel.org \
    --subject='Re: [vm] writing to UDF DVD+RW (/dev/sr0) while under memory pressure: box ==> doorstop' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).