On 10 Oct 2015, at 16:34, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Sat, 10 Oct 2015, Paul Jones wrote: > >>>> Why is Windows so much faster? Or to put it another way, why is Linux >>>> slow? How can we improve things? >>> >>> I don't know. We were doing our performance demos using Windows, so we >>> never looked into why Linux was slower. But I do know the Microsoft >>> engineers put some effort into tuning their stack for good performance >>> at USB 3.0 speeds. I don't think anyone has done that for Linux yet. >> It seems that Mac OSX is faster when using a file system on an emulated device. >> dd directly to the block device on my Mac gives me around 137MB/s, whilst copying data onto a mounted filesystem (also with dd) runs at over 180MB/s. > > I don't see how this comment is relevant to the question at hand, > namely, why does the mass-storage gadget run faster when attached to a > Windows host than when attached to a Linux host. > > I also don't see how "an emulated device" fits in here. In both tests, > you copied data to a block device: once directly and once through the > filesystem. Nothing was emulated. It’s emulated in the sense that I’m using a gadget to provide a RAM based device. > Finally, are you sure you are seeing the actual throughput and not just > the rate of copying into a page cache? It would be better to test > using reads instead of writes, because a read can't complete before > the data is retrieved from the device. Oops, the numbers above are for reading (not writing which is somewhat slower). Paul. -- 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
