To: Jens Axboe <axboe@suse.de>
Cc: David Chinner <dgc@sgi.com>, Neil Brown <neilb@suse.de>,
       linux-kernel@vger.kernel.org, akpm@osdl.org
Subject: Re: RFC - how to balance Dirty+Writeback in the face of slow  writeback.
References: <17633.2524.95912.960672@cse.unsw.edu.au>
	<20060815010611.7dc08fb1.akpm@osdl.org>
	<20060815230050.GB51703024@melbourne.sgi.com>
	<17635.60378.733953.956807@cse.unsw.edu.au>
	<20060816231448.cc71fde7.akpm@osdl.org>
	<20060818001102.GW51703024@melbourne.sgi.com>
	<20060817232942.c35b1371.akpm@osdl.org> <20060818070314.GE798@suse.de>
From: Andi Kleen <ak@suse.de>
Date: 18 Aug 2006 20:57:31 +0200
In-Reply-To: <20060818070314.GE798@suse.de>
Message-ID: <p73hd0998is.fsf@verdi.suse.de>
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Jens Axboe <axboe@suse.de> writes:

> On Thu, Aug 17 2006, Andrew Morton wrote:
> > It seems that the many-writers-to-different-disks workloads don't happen
> > very often.  We know this because
> > 
> > a) The 2.4 performance is utterly awful, and I never saw anybody
> >    complain and
> 
> Talk to some of the people that used DVD-RAM devices (or other
> excruciatingly slow writers) on their system, and they would disagree
> violently :-)

I hit this recently while doing backups to a slow external USB disk.
The system was quite unusable (some commands blocked for over a minute)

-Andi
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