Message-ID: <407428F3.90004@pobox.com>
Date: Wed, 07 Apr 2004 12:14:43 -0400
From: Jeff Garzik <jgarzik@pobox.com>
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To: mike.miller@hp.com
CC: alpm@odsl.org, axboe@suse.de, linux-kernel@vger.kernel.org
Subject: Re: cciss updates for 2.6.6xxx [1/2]
References: <20040406201030.GB2554@beardog.cca.cpqcorp.net>
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mikem@beardog.cca.cpqcorp.net wrote:
> This patch adds per logical device queues to the HP cciss driver. It currently only implements a single lock but when time permits I will provide that funtionality. Thanks to Jeff Garzik for providing some sample code.
> This patch built against 2.6.5. Please consider this for inclusion.


I appreciate the credit but I don't see that it addressed my original 
objection -- the starvation issue.

Do you cap the number of per-array requests a "1024 / n_arrays", or 
something like that?  You mentioned that the hardware has a maximum of 
1024 outstanding commands, for all devices.  The two typical solutions 
are a round-robin queue (see carmel.c) or limiting each array such that 
if all arrays are full of commands, the total outstanding never exceeds 
1024.

This patch may be OK for -mm, I would rather not see it go upstream -- 
it seems to me you are choosing to decrease stability to obtain a 
performance increase.  I think you can increase performance without 
decreasing stability.

	Jeff


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