I discovered from looking at the mpiP profiler that OMPI always uses gettimeofday rather than clock_gettime to implement mpi_wtime on GNU/Linux, and that looks sub-optimal. I don't remember what the resolution of gettimeofday is in practice, but I did need to write a drop-in replacement for benchmarks. [mpiP expects mpi_wtime to be high resolution, and you have to configure if for clock_gettime explicitly.]
Before I raise an issue: is there some good reason not to use clock_gettime, especially as gettimeofday is obsolete in POSIX? I guess not, especially as the VT component uses clock_gettime.
