[Xen-devel] pvusb performance

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

Noboru,

My pvUSB windows driver is now working at a very basic level (flash
memory stick), and I'm conscious of the fact that I only send one
request on the ring at a time and have to wait for it to complete before
I can put the next one on. Can this be improved?

I think maybe it can't with your current usbback driver - there would
need to be some mechanism to flush the ring of all subsequent requests
in the case of an error, eg when I get a 'Read 65536 bytes' request from
Windows, I do this:

. Put read request command on ring
. Wait for response
. Put data request on ring for first 512 bytes
. Wait for response
. Put data request on ring for next 512 bytes
. etc
. etc

If there is a buffer underrun, I can see no way for Linux to do
something with the subsequent data requests... it would need to do
something like put the ring into a error/underrun condition and 'eat'
all the requests until a clear error request came down the ring.

Or maybe this is already part of the design?

Thanks

James


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