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From: Mike Galbraith <efault@gmx.de>
To: Andrew Morton <akpm@linux-foundation.org>
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, 08 Jan 2008 16:21:53 +0100	[thread overview]
Message-ID: <1199805713.3571.12.camel@homer.simson.net> (raw)
In-Reply-To: <20080108033801.40d0043a.akpm@linux-foundation.org>


On Tue, 2008-01-08 at 03:38 -0800, Andrew Morton wrote:
> On Tue, 08 Jan 2008 12:05:16 +0100 Mike Galbraith <efault@gmx.de> wrote:

> > 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.

Yes, with UDF, the IO was _incredibly_ slow.  With ext2, it was better,
though still very bad.  I tested with that other OS, and it gets ~same
throughput with UDF as I got with ext2 (ick).

UDF does udf_clear_inode() -> write_inode_now(inode, 1)

I suppose I could try write_inode_now(inode, 0).  Might unstick the box.

	-Mike


  reply	other threads:[~2008-01-08 15:22 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-04 11:46 [vm] writing to UDF DVD+RW (/dev/sr0) while under memory pressure: box ==> doorstop 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
2008-01-08 15:21           ` Mike Galbraith [this message]
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

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