Hi Peter
I think what's happening for UDP is the buffer is copied in at the
socket and
maintained so they can be locked down once for DMA by the driver, which
means for UDP we can have one large datagram. UDP remains unchanged,
when the buffer hits either IPv4 or IPv6 then the datagram goes through an
MDT setup function which would create a second buffer for the headers, doing
IP fragmentation on the UDP datagram with the Fragmented IP headers going
to the header buffer. When the completed MDT message hits a MDT capable
driver then the software locks down the two buffers and then starts filling
descriptors.
The single call to the driver and the 2 calls to the DMA setup
function is the
main source of the accelerated capability of MDT, much like LSO.
Frank
Peter Memishian wrote:
> > LSO doesn't work as well as MDT, Also the hardware I'm working with
> > has no UDP LSO capability, does any?
>
> I don't see any support in our UDP module for MDT. Others more familiar
> with the latest hardware could speak to the UDP LSO question, but I'd
> heard rumors that some Neterion ASICs could do it.
>
> --
> meem
>
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