[openib-general] APM support in openib stack

[Tang, Changqing]

> > I understand that you considering to go on an approach 
> which does not 
> > involve librdmacm, so you would probably like to
> > 
> > 	+ use IB PORT GIDs at your initial mpi init exchange
> > 	+ issue IB SA Path query via libibsa (which does not exist)
> 
> likely multipath query if you want APM

Yes, we want to have APM as well.


> 
> > 	+ establish IB RC connection (listen/connect/accept) via libibcm
> > 
> > Please note that such an approach is possible even with the non 
> > existence of libibsa (similarly to what IB MPIs do today 
> use IB PORT 
> > LIDs [note you would need both GIDs & LIDs to have the CM working 
> > fine]
> 
> There are other possibilities here too using inband (IB) exchanges.
> libibsa is not that far away either. What is your time frame ?

Is it possible to have it in OFED 1.2 ?


> 
> > at your ranks pre exchange and hardcode the other IB PATH 
> params such 
> > as MTU, PKEY and SL you set later into the IB RC QP.
> > 
> > However, a no rdma cm approach means you need to apply 
> hacks to "guess" 
> > the correct pkey, mtu and sl and some more limitations that 
> eventually 
> > you would face when coming to advanced IB deployment environments.
> 
> Also, you would make more work if iWARP support is of 
> interest as well.
> It comes "for free" or at least "for cheap" if the RDMA CM 
> approach is taken.

We understand that, but we hope to have a connect/accept style IB
connection setup, without IPoIB involved,
like HP-UX IT-API(similar to uDAPL without underlying IP support), it
works with multiple cards.

Configure 4-5 IP addresses on a single node is kind of silly.



--CQ


> 
> -- Hal
> 
> > All you have to do to use the rdma cm to require a functional IPoIB 
> > NIC on each of the active IB PORTs, which is a trivial requirement 
> > from the users in the Ethernet world, so why not apply it 
> here as well ???
> > 
> > On the other hand moving to use the IB CM instead of 
> emulating it via 
> > TCP is some progress...
> > 
> > Or.
> > 
> > 
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