On 11/04/13 18:17, Tim Roberts wrote: > Toby Gray wrote: >> We've been looking into the performance of the Windows desktop and >> Windows CE versions of libusbx compared to Linux on the same hardware. >> The event handling in Windows and Windows CE appears to take >> considerably longer than for Linux. >> >> This is understandable given the way that the windows backends need to >> pretend to have fds for the core of libusbx to process. > Can you share with the performance numbers you have and a short > description of how you got them? You've made me really curious here. > Intuitively, I would have guessed that whatever fd futzing was going on > was absolutely insignificant when compared to the overhead of > user/kernel transitions and user event processing. >
The only numbers which would probably make sense to others are that we noticed that there was a long time between the short packet of the end of a transfer and the host issuing the next IN token for that endpoint. The gap is multiple milliseconds in length on WinCE, but not when the same board is running a Linux image. We have finally got around to making sure that we have multiple concurrent bulk in transfers to eliminate this latency. I know that we should have been doing this from the start, but higher priority things had always got in the way and the event handling in Linux was fast enough for us to get away with it. So it's now a case of reducing the CPU time that we see in the processing of events. We've not drilled down fair enough yet to discover exactly where the time goes. When I do get time to create a working patch series I'll be sure to include meaningful figures from benchmarks which others will be able to reproduce. I appreciate that without this information it would just be large code churn with no way of gauging how much it helps. Regards, Toby ------------------------------------------------------------------------------ Precog is a next-generation analytics platform capable of advanced analytics on semi-structured data. The platform includes APIs for building apps and a phenomenal toolset for data science. Developers can use our toolset for easy data analysis & visualization. Get a free account! http://www2.precog.com/precogplatform/slashdotnewsletter _______________________________________________ libusbx-devel mailing list libusbx-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libusbx-devel
