[ovs-discuss] Q: RDMA tunnel support in openvswitch

Jesse Gross jesse at nicira.com
Tue Oct 2 18:16:31 UTC 2012


On Tue, Oct 2, 2012 at 4:08 AM, Alexey I. Froloff <raorn at raorn.name> wrote:
> Hi,
>
> While openvswitch does not support InfiniBand natively, it is
> still possible to use IB features.  One can create GRE tunnels
> with endpoints on IPoverIB interface.
>
> Recently I've come to an idea to use RDMA for tunneling packets
> between hypervisors.
>
> Since all tunnels are point to point, one can create new port
> with type, say, "rdma", provide connection parameters, like
> local/remote verbs and so on.  From now on, packets that sent to
> this ports will be transferred to remote via RDMA.
>
> I have found sample kernel module that does rdma transfer of a
> memory region between two nodes.  I've also looked into
> openvswitch sources and think that this feature could be
> implemented without redisign.
>
> Are you interested in that functionality?  If yes, I can start
> working on that.  I have text editor, compiler and InfiniBand
> fabric available for testing.

Where specifically do you think that this will improve performance?
Since these packets will already be in the kernel and need to be
sent/received as skbs on the OVS side, the effect seems very similar
to the normal DMA of packets to the NIC.  It's not quite the same as
if you are directly placing data into an application buffer - the only
potential benefit that I could see is maybe you can handle larger
packets.  I don't know Infiniband well so it's possible that I'm wrong
but I suspect that you will end up with something very similar to the
existing network infrastructure.

The other issue that I see is that presumably this involves some form
of protocol to transmit the encapsulated Ethernet packets.  Is there
an existing protocol that you were planning on using?  I know EoIB has
been proposed but I don't think that's what you're planning.  If not,
I would be very reluctant to put something completely new into the
tree.



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