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xen-devel
Re: [Xen-devel] pvusb performance
James,
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.
Regards,
Noboru
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