usb2 bulk read optimization ?

[Hans Petter Selasky]

On Saturday 29 November 2008, Thierry Herbelot wrote:

> > Hi Thierry,
> >
> > You have found the correct place to tune the buffer size. Are you sure
> > that your application is also doing similiarly large bulk transfers?
>
> I'm doing "usb_bulk_read(handle, ep, data, size, 500);" with size around
> 40kbytes.
>
> > Are you sure that the transfer speed limitation is not a limitation of
> > your USB device?
>
> this USB device is known, with a different, open-source, OS, to handle
> around 240Mbps (30Mbyte/s, but probably not on this oldish machine). the
> device is high-speed compliant, but can only do bulk transfers (maybe
> isochronous could have been better, but that's technically not possible)
>
> > Keep in mind: The EHCI has an interrupt clamp of 4000-8000 interrupts /
> > second.
>
> OK : I would *very much* like to see a transfer rate of 4k*40kbyte/sec
>

Check with "usbconfig" which speed your device is running at.

Also check "vmstat -i" to see the actual interrupt rate.

--HPS