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
Date: Thu, 18 Feb 2010 10:16:03 +0000 [thread overview]
Message-ID: <20100218101603.23c16786@lxorguk.ukuu.org.uk> (raw)
In-Reply-To: <4B7CCC7E.3060108@teksavvy.com>
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
next prev parent reply other threads:[~2010-02-18 10:19 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-17 13:10 Alan Cox
2010-02-17 13:11 ` [RFC 2/4] libata: Remove excess delay in the tf_load path Alan Cox
2010-02-17 13:13 ` [RFC 3/4] libata: Remove excess command issue delays Alan Cox
2010-02-17 14:10 ` Sergei Shtylyov
2010-02-17 15:34 ` Alan Cox
2010-02-17 13:15 ` [RFC 4/4] libata: Make sil680 do its own exec_command posting Alan Cox
2010-02-18 5:13 ` [RFC 1/4] libata: cache device select Mark Lord
2010-02-18 10:16 ` Alan Cox [this message]
2010-03-01 20:15 ` Jeff Garzik
2010-03-02 17:28 ` Alan Cox
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