On Fri, 16 May 2003, Robin Humble wrote:
> The pipeline depth of Xeon is also _huge_ which slows down lots of
> simple operations (eg. gettimeofday, routing, ...). Athlon has a
> much shorter pipeline. LAM seems to call gettimeofday a lot.
Just a quick note - LAM will call gettimeofday a *lot* when MPI tracing is
enabled. Otherwise, it really shouldn't be calling gettimeofday all that
often (for the time related MPI function calls and possibly during
MPI_INIT). Tracing is off by default if an application is started by
mpirun, but can be enabled by the -ton switch to mpirun.
If you seeing lots of calls to gettimeofday from your MPI application, you
might want to make sure tracing isn't on. In addition to the gettimeofday
calls, there are other aspects of the tracing system that can reduce
performance.
Hope this helps,
Brian
--
Brian Barrett
LAM/MPI developer and all around nice guy
Have a LAM/MPI day: http://www.lam-mpi.org/
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