Date: Thu, 8 Nov 2001 17:34:04 -0500
From: Johannes Erdfelt <johannes@erdfelt.com>
To: Tim Pepper <tpepper@vato.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Big USB speed difference when compiled as module (was Re: speed difference between using hard-linked and modular drives?)
Message-ID: <20011108173404.L32355@sventech.com>
In-Reply-To: <20011108142412.A19451@vato.org>
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In-Reply-To: <20011108142412.A19451@vato.org>; from tpepper@vato.org on Thu, Nov 08, 2001 at 02:24:12PM -0800
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On Thu, Nov 08, 2001, Tim Pepper <tpepper@vato.org> wrote:
> On Thu 08 Nov at 17:01:24 +0100 roy@karlsbakk.net done said:
> > 
> > Are there any speed difference between hard-linked device drivers and
> > their modular counterparts?
> 
> I've been wondering this as well.  I've got a curious situation:  With usbcore
> and the uhci driver compiled into the kernel I can initiate transfers to a usb
> device I have (Creative Nomad Jukebox) at what I'm eyeballing to be near the
> 12Mbps USB speed.  These tranfers always fail.  With both drivers compiled as
> modules the transfers are over an order of magnitude slower, not even
> appearing to reach the 1.5Mbps USB speed, but they succeed.  I haven't had a
> chance to try to figure out what's going on for sure.
> 
> It's been a little while since I was playing with this but I believe I saw
> the same thing with the usb-uhci driver as well but it didn't seem to like
> talking to the Nomad regardless of it being compiled as a module or not.
> This was with the 2.4.13 kernel.  I can provide more details upon request.

This absolutely should not be the result of compiling into the kernel.
It's most likely a bug in the HC which just happened to show up with
modules.

> BTW: is there a way to do USB sniffing in software in linux?  I'd imagine it's
> possible, but just can't find anything that does...

Not in Linux yet.

JE

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