[ofa-general] Can we provide a qp_num when creating a QP ?

[Tang, Changqing]

HI, Roland or other engineers:

        I have asked this question before. To wire a QP connection, each side need to know
peer's side port lid and qp_num. For MPI with many ranks, this is an alltoall exchange.

        If we can create a QP with provided qp_num, then MPI does not need the qp_num
exchange, for a QP-pair between two processes, MPI can figure out peer QP's qp_num. So
we can eliminate the third-party channel to exchange information, and speedup the startup
time.

        Curently qp_num is always a return value from the driver. If we can suggest a qp_num
when creating a QP, and the qp_num is already used, then IBV can either error out, or
pick up another number for app.


Thanks.
--CQ