[ofa-general] Re: multicast join failed for...

[Hal Rosenstock]

On Fri, 2007-04-13 at 09:38, Michael S. Tsirkin wrote:
> > > If the group is created at a lower rate, there would be no problem.
> > > But the default configuration should be "plug an play".
> > 
> > So you are arguing for 1x SDR as the default. We've discussed and
> > disagreed on this before as I think it masks performance issues and
> > those are harder to find. I could be wrong about this.
> 
> No, I'm arguing for dynamic configuration as the default.
> so we start at 4x DDR and bbring the rate down as slower nodes join.

OK that answers a different question I was wondering about. Or speed it
up if all nodes are say 4x DDR.

What I was trying to say was that since we don't have dynamic rate
support now (and I'm not signing up to do this, is someone ?), I was
saying that a static rate default of 1x SDR would eliminate the join
errors (at the debug "expense" of what I think are harder to find
performance issues). Sorry I didn't make that clear before.

-- Hal

> > > > ipoib multicast performance doesn't seem that critical.
> > > 
> > > This is a policy than can be made optional, but should not
> > > be forced on users by default.
> > > 
> > > > Whereas disrupting
> > > > other multicast groups, which could actively be in use by MPI, may be. 
> > > 
> > > The disruption would be very minor - this would happen at most once when rate changes
> > > from DDR to SDR and once when it changes back.
> > 
> > In frequency it may be minor. It affects other things that should not be
> > affected. Perhaps that is just a shortcoming of the mechanism underneath
> > and that can/should be improved.
> 
> Yes, I agree.
>