iWARP support

[shamisp]

This is something that came up within OpenMPI community.
They aim to retire OpenIB BTL in 4.x and replace it is with "UCT" btl.
As for now, the only concern is Iwarp support. I have no idea if we have somebody within community testing it...

[hppritcha]

well we're not going to do that if UCX doesn't support connectx3

[shamisp]

You are saying we do not support cx3 ? @YossefE

[mike-dubman]

ConnectX-3 is NOT i-warp capable device.
UCX supports ConnectX-3 device through verbs.
seems some kind of misunderstanding here.

[marmistrz]

At @golemfactory we're testing the rxe and siw drivers for MPI with RDMA over 1GigE/10GigE. When iWARP support is implemented in UCX, we'll be happy to test this feature and its performance in comparison to rxe+ucx.

[yosefe]

currently the main missing items for iWarp support are:

• boostrap RC transport over rdma_cm instead of over UD
• use RC without shared receive queue