Re: [Discuss-gnuradio] Using USRP from multiple applications simultaneously

[Harald Welte]

mh, yet another comment on zerocopy.  I wish there was a reply to my
question on the usb-multiple-interface issue ;)

On Sun, May 01, 2005 at 10:25:15PM +0200, Stephane Fillod wrote:

> "Premature optimization is the root of all evil", Donald Knuth.

Mh, that's my common mistake.  I always over-optimize in the beginning,
and software takes ages until it's actually released.  Still I can't
help.

> Before implementing, verify that this is the biggest spot of
> optimization. You can use great tools like OProfile for that purpose.

It just hurts to see waste valuable cpu time, memory bandwidth and cache
pollution in a case that at least appears to be very easily optimizied.

I was probably spending man-months to see how to optimize kernel
networking code, where we can't do all those neat optimizations that
seem perfectly possible with USB. 

> Do you(or somebody else) know a more clever kernel/user interface 
> with zero-copy for the USB subsystem?

there is none.  That's what my point was about.  Implementing mmap() on
the filedescriptor in usbdevfs.

> I guess now we're more in functional development, but it's always
> open on who has spare time ;-)

I don't have the time, but the problem seems interesting enough to find
some time for it.

-- 
- Harald Welte <address@hidden>                         http://gnumonks.org/
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