Re: Big USB speed difference when compiled as module (was Re: speed difference between using hard-linked and modular drives?)

[Johannes Erdfelt]

On Thu, Nov 08, 2001, Tim Pepper <[e-mail]> wrote:
> On Thu 08 Nov at 17:01:24 +0100 [e-mail] 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