Subject: Re: Linux 2.4.18-pre9-ac1
To: axboe@suse.de (Jens Axboe)
Date: Tue, 12 Feb 2002 14:35:18 +0000 (GMT)
Cc: alan@lxorguk.ukuu.org.uk (Alan Cox), andersen@codepoet.org,
        linux-kernel@vger.kernel.org
In-Reply-To: <20020212092658.Z729@suse.de> from "Jens Axboe" at Feb 12, 2002 09:26:58 AM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Sender: linux-kernel-owner@vger.kernel.org

> > > I want to find out why it was done first and then test it. Leaving it out
> > > will ensure it bugs me until I test it
> > 
> > If you leave it out, you surely want to make sure that the other request
> > init and re-init paths agree on the clustering for MO devices. Because
> > they don't.

No - I want to run a test set with an M/O drive before and after the change
and see what it shows in real life. I suspect nothing much.

> Now, disabling request merging for MO devices might make a whole lot
> more sense. That might be worth while trying, and I'd be happy to give
> you a patch to try that out instead.

I don't think that should be required actually. The killer on M/O disks
is seek time, and to an extent rotational latency (its 3 trips round a 
cheaper M/O disk to rewrite a sector). If anything clustering writes to
the same track should be a big win.

Alan
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