[ovs-discuss] Fw: TSO not working for VM iperf data packets.

[Jesse Gross]

On Sat, Dec 19, 2015 at 7:26 AM, Piyush R Srivastava1 <pirsriva at in.ibm.com>
wrote:

> Hi,
>
> One other thing i noticed is that... For starting I DO SEE offloaded
> packets... However, after a few initial packets, Offloading seems to be
> reduced drastically and i see purely 1464 sized Ethernet Frames.
>
[...]

> This seem to suggests that the issue is for the packets that are getting
> encapsulated at compute node and decapsulated at Network Node only
> We are using software GRO patch mentioned here at Network Nodes-
> http://openvswitch.org/pipermail/dev/2015-August/059335.html
>
> Does this info help in debugging the issue?
>

There is no issue then. GRO is simply best effort aggregation and does not
wait to get a full 64k frame so when the packet is transmitted on the
physical NIC, TSO will be limited what was aggregated. You're only
guaranteed to get big TSO packets all the time when you generate them on
the local machine like you did in your later tests.
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