[openib-general] RFC MPI and app. requirements of OpenIB

[Sean Hefty]

>I'm soliciting feedback from the MPI and other application developers regarding
>which OpenIB APIs they will be targeting with their implementations.
>Specifically, myself and some of the other IB developers are interesting in
>knowing if userspace applications will be written to the RDMA CMA interface,
>the
>IB CM API, or some other abstraction.

To help clarify the trade-offs:

The CMA allows the use of IP addressing for connection establishment and
abstracts device hotplug.  It also operates over any type of RDMA device.

A disadvantage of using the CMA is that it may not select the best set of paths
between two or more nodes.  The IB CM also permits path failover on a single
HCA.  Use of the IB CM requires that clients also interface with the IB SA to
obtain path records.

My personal recommendation would be for applications to use the CMA, but that
does result in losing some flexibility.

- Sean