On Friday 28 January 2011 02:44:43 Daniel O'Connor wrote: > On 23/01/2011, at 24:03, Hans Petter Selasky wrote: > > You need to change the way you buffer the data. FreeBSD does not queue > > more than 2 URB's at any time, and the turnaround time varies from 1ms > > to 125us due to hardware IRQ restrictions. Linux queues up all it can > > get, which leads to other kind of problems. The current internal buffer > > limit is 16Kbyte 8000 times per second which gives a MAX of 128 > > MByte/second. > > How difficult would it be to increase this?
Hi, For this kind of applications ISOCHRONOUS transfers should be used. Then you can have a double buffer guard in the range 1-56ms, regardless of the buffer size the hardware uses. You could also try an XHCI controller, because the BULK buffering is done differently there. > I obviously don't need any more > throughput, however my application is very sensitive to latency, as I am > reading out of a fairly small FIFO and if it fills up my entire run has to > be aborted. --HPS _______________________________________________ email@example.com mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-usb To unsubscribe, send any mail to "freebsd-usb-unsubscr...@freebsd.org"