[ewg] Tools to diagnose rdma performance issue?

[Doug Ledford]

On 08/15/2013 11:21 AM, Chen, Mei-Jen wrote:
> Is it typical that rdma/verbs have much more overhead than MPI
> (because of do verbs processing on the CPUs)?

No, MPI has more overhead than verbs.  However, the verbs libraries and
kernel driver handle everything on a single CPU whereas PSM is
multithreaded and splits the load across multiple CPUs.  So even though
there is extra overhead from using MPI, the benefit of getting multiple
CPUs involved via PSM outweighs the overhead.