[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] pvusb performance
> > > Okay maybe I'm a bit confused then. > > > > When Windows gave me a URB with 65536 bytes of data, I set buffer_length > > to 65536 and filled up the SG registers accordingly, but usbback gave me > > an error. When I break it into 512 byte (packet size) chunks it works > > okay. I just assumed that you have to give usbback requests with less > > that 'max packet size' of data. > > > > Maybe the cause of my error was somewhere else? I'll try it again. > > If you transfer 65536 bytes of data, you should change the > USBIF_MAX_SEGMENTS_PER_REQUESTS value to 16 or more. > It is defined in include/xen/interface/io/usbif.h > You need to recompile the drivers. > > Request size and MAX_RING_SIZE are trade-off. > I defined this value empirically. > If the value is about up to 20, it doesn't affect the performance > of memory stick. > D'oh! I feel like a complete fool :) Yes, 10 * 4096 is much less than 65536 - that will explain it! I don't think I can tell windows to send me less data, which might be a bit of a pain. Still, I can still get it working by breaking the request into 40960 byte chunks. Thanks for clearing that up for me. Arithmetic has never been my strong point :) James _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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