Date: Thu, 18 Feb 2010 10:16:03 +0000
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Mark Lord <kernel@teksavvy.com>
Cc: Alan Cox <alan@linux.intel.com>, jeff@garzik.org.com,
       linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org
Subject: Re: [RFC 1/4] libata: cache device select
Message-ID: <20100218101603.23c16786@lxorguk.ukuu.org.uk>
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	<4B7CCC7E.3060108@teksavvy.com>
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O> I totally agree with this patch, but question the timings used to justify it.
> Surely the overhead is only 1-2usec for the case where the device
> is the one that was already selected (on a "smart" interface) ?

IFF you have a smart interface. A lot of the controllers in the PCI space
don't appear to be that clever.

> And for the case where the currently selected device is different
> than the desired device (the 1msec case), this patch makes little/no difference?

Correct, but even with two devices per cable (which is not the most
common setup) you win. Worst case (which I've never seen) you draw.

Alan
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