RE: [Xen-users] Release 0.8.0 of GPL PV Drivers for Windows

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

> 
> > That's because with some version of xen and/or drivers (I'm not sure
> > actually) it was a known fact that performance got bad when you had
hw
> > checksum calculations turned on..
> >
> > So just to see if that's the case here.. I guess this was mostly for
> domU..
> 
> Ahh, because there's no hardware - makes sense.

Actually, csum offload in theory should work just fine when there is no
hardware. If all 'virtual' parties attached to the bridge don't care
about checksums (because blkback has told them that the data is
validated) then nobody has to check and things can go faster. Otherwise,
the sender has to calculate a correct checksum for outgoing packets, and
the receiver has to also calculate the correct checksum for incoming
packets and confirm that it is correct.

James


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