linux-kernel - Re: [vm] writing to UDF DVD+RW (/dev/sr0) while under memory pressure: box ==> doorstop

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Message-Id: <1199806071.4174.2.camel@homer.simson.net>
Date:	Tue, 08 Jan 2008 16:27:51 +0100
From:	Mike Galbraith <efault@....de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [vm] writing to UDF DVD+RW (/dev/sr0) while under memory
	pressure: box ==> doorstop


On Tue, 2008-01-08 at 16:21 +0100, Mike Galbraith wrote:
> On Tue, 2008-01-08 at 03:38 -0800, Andrew Morton wrote:
> > 
> > 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.

(nope, still sync, UDF still deadly)

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