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

[Michael S. Tsirkin]

> Quoting Or Gerlitz <ogerlitz at voltaire.com>:
> Subject: Re: [Bug 506] IPoIB IPv4 multicast throughput is poor
> 
> 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.

I think so too. So what does the test do? Is it a sendonly join?

> >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.

That's what I'd expect.


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MST