[ofa-general] Re: [Bug 506] IPoIB IPv4 multicast throughput is poor

[Or Gerlitz]

Michael S. Tsirkin wrote:
>> The low throughput is a major issue, though.  Shouldn't the IP multicast
>> throughput be similar to the UDP unicast throughput?

> Is the send side a send only member of multicast group, or full member?

The join state (full / sendonly nonmember / nonmember)is something 
communicated between the ULP through the ib_sa module and the IB SA.
I don't see how the host ib driver becomes aware to it.

The current ipoib implementation for sendonly joins is to join as full 
member but not to attach its UD QP for that group.

> If it's a full join, HCA creates extra loopback traffic which
> has then to be discarded, and which might explain performance degradation.

Can you explain what --is-- the trigger for the "looback channel" 
creation? my thinking it should be conditioned on having any QP attached 
to this MGID, which does not seem the case in this scenario.

Or.