On Fri, Jul 16, 2010 at 11:30:19AM -0400, Don Zickus wrote: > Hi Sarah, > > My name is Don Zickus and I am going to be responsible for keeping USB and > friends happy in RHEL-6. We were doing some performance testing with USB3 > and notice it didn't seem to be as fast as some of the windows benchmarks. > > I wanted to know what your expectations were for throughput with USB3 > devices and controllers were, so I could communicate them if people > complained. > > The USB components is mostly based on 2.6.32 + stable fixes to give you a > baseline. Hmm, ok. If you're not taking feature patches from the other kernels, then you're not going to get isochronous endpoint support, which means no one's webcam will work. But I know you have to draw the line somewhere. > We have been using 'hdparm -t' as our quick and dirty performance tool > with the usb3 harddrives we have. Sure. dd works well too. > Using a WD My Book 3 we get about 25MB/s throughput and a Buffalo HXU3 > gets about 82MB/s. Various test with Windows showed higher numbers, like > 80MB/s and 102MB/s respectively. > > Just trying to figure out if the bottleneck is a scsi or a usb problem. I'm working on a set of performance patches for xHCI, based on 2.6.35. One of the bigger patches adds MSI support, which means other interrupt handlers aren't called when the xHCI hardware interrupts. This is really important if xHCI shares an interrupt with say, UHCI, because the UHCI interrupt handler is horrible. The patches also do things like remove unnecessary register reads and move some functions into better places so the compiler can optimize them. They haven't made it into mainline yet though. > Also it seems like USB3 is still going through a bunch of churn. Yes, the xHCI driver is still very much under development. I expect that to start to trail off in the second half of the year. > Any heads up on good chunks to have or to look out for would be great > to help promote USB3 on RHEL-6. Thanks! Well, I suppose it depends on what you want. Do you need interrupt endpoint support (for mice, keyboards, etc)? Support for resetting devices? Support for alternate interface settings? I think all of these features made it into kernels after 2.6.32. Sarah Sharp -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
