Date: Sat, 29 Nov 2008 08:54:00 +0100 From: Hans Petter Selasky <hselasky@c2i.net> To: Thierry Herbelot <thierry.herbelot@free.fr> Cc: freebsd-usb@freebsd.org Subject: Re: usb2 bulk read optimization ? Message-ID: <200811290854.01531.hselasky@c2i.net> In-Reply-To: <200811290031.22513.thierry.herbelot@free.fr> References: <200811281606.51927.thierry.herbelot@free.fr> <200811281906.00913.hselasky@c2i.net> <200811290031.22513.thierry.herbelot@free.fr>
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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
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