Date: Fri, 28 Jan 2011 12:14:43 +1030 From: "Daniel O'Connor" <doconnor@gsoft.com.au> To: Hans Petter Selasky <hselasky@c2i.net> Cc: freebsd-usb@freebsd.org Subject: Re: libusb performance on 8.1 Message-ID: <6AD22899-0B00-483D-A01E-786029A82C9F@gsoft.com.au> In-Reply-To: <201101221433.23194.hselasky@c2i.net> References: <9CF6C32F-E230-446B-94FC-C57F0F02B0E4@gsoft.com.au> <201101221433.23194.hselasky@c2i.net>
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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=20 > than 2 URB's at any time, and the turnaround time varies from 1ms to = 125us due=20 > to hardware IRQ restrictions. Linux queues up all it can get, which = leads to=20 > other kind of problems. The current internal buffer limit is 16Kbyte = 8000=20 > times per second which gives a MAX of 128 MByte/second. How difficult would it be to increase this? 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. -- Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C
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