usb2 bulk read optimization ?
Hans Petter Selasky
hselasky at c2i.net
Fri Nov 28 23:51:49 PST 2008
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
> > 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.
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