One starnge thing that I see on the protocol Analyser is that,even within a URB after we receive the ACK for one OUT packet the host sends the next OUT packet after 4-5 microseconds (and I suppose that this is due to some hardware latency, as software has no controller once the URB i submitted).
Now if we consider this 4microsecond then time to transmit one packet of 512 byte is approximately 14microseconds. Which means a throughput of approximately 292Mbps. So to me it seems theat this is the maximum that I could achieve, even if I remove my all software latencies. Can anybody tell me the reason for this 4-5microescond, time. Or is there any way to remove this JUhee -----Original Message----- From: Alan Stern [mailto:[EMAIL PROTECTED] Sent: Tuesday, May 09, 2006 8:10 PM To: Juhee MALA Cc: linux-usb-devel@lists.sourceforge.net Subject: Re: [linux-usb-devel] USB Host performance On Tue, 9 May 2006, Juhee MALA wrote: > We are using Linux USB Host stack and doing some performance analysis. > For performance analysis we are testing it with a device, which > accepts the Bulk-OUT packets with full effieciency (not much-NYTES > from device side). We are submitting the data of URB size 8kbytes. The > throughput in such scenario that we are getting is approximately > 175Mbps. > > 1. Can anybody tell me, if this is a good performance? Good for what? It's certainly not the best possible. But it's more than adequate for USB-audio. > 2. Can anybody tell me what is the best performance that can be > achieved on a USB host? The maximum theoretical throughput for high-speed 512-byte bulk transfers is 13 packets per microframe, or 53248000 B/s. That's equivalent to 426 million bits per second. Linux can achieve such rates, if the hardware allows. To reach it, you have to submit a lot of URBs asynchronously. If you're using 8 KB transfer lengths then you should submit at least two batches of URBs, with at least 64 URBs in each batch, and with the URB_NO_INTERRUPT flag set on each URB except the last one in a batch. Each time a batch completes, immediately submit another batch. > 3. IS there any bench marking tool for checking the host stack > performance? Not that I know of. > 4. Which application should be used for demonstrating the host > performance? This is almost the same question as number 3. If you want to use your test device, you should select an application that will work with it. Of course, since I don't know what your test device is, I can't recommend any applications. Alan Stern ------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid0709&bid&3057&dat1642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
