High-speed transfers

Thierry Herbelot thierry at herbelot.com
Sat Jul 1 14:24:29 UTC 2006

Le Saturday 1 July 2006 15:31, Hans Petter Selasky a écrit :
> Yes, but don't forget high-speed USB transfers. They require larger
> buffers. For example 1024 bytes for ULPT is too little. The interrupt rate
> will be so high, that it is unrealistic to transfer 20MB/s using 1024 byte
> interrupts. My rewritten ULPT now uses "2*(1<<17)" buffers.


I wonder what kind of speed you are getting : I would like to see improvements 
for reads (and writes) on standard endpoints, without having to resort to 
writing specific drivers (using ugen on the standard FreeBSD USB stack).

One goal would be to achieve something like 25 to 30 Mbytes/s, sustained, 
(finally getting to some interesting fraction of the peak USB2 data rate).


PS : from experience, 300Mbps can be sustained on a decent PC, using for 
example Suse 10.1 (but don't try with an ATI southbridge : they suck)

More information about the freebsd-hackers mailing list