Hello Open MPI developers, I've been away from the Open MPI code for a long time now, but I just ran across this article that should give developers second thoughts about using mmap'ed files in performance critical situations.
"Deferring mtime and ctime updates" http://lwn.net/SubscriberLink/564120/bdc189d08c512761/ I might suggest an audit of the Open MPI code base for mmap calls to make sure they are all needed, or if they can be done a different way, especially in the coll and sm btl. Yes, the article is about a patchset to lessen the performance problem, but until that gets into the kernel, and into the distributions, and into the parallel machines, this could be a source of lost performance in Open MPI. I seem to recall some work was done after I left development to make use of POSIX or SYSV shared memory system calls that avoided having an associated backing-store file. But I don't remember if those became the default, or if mmap'ed files was still the default. Anyway, back to lurking on the mailing lists for me. P.S. - Darn, my timat...@open-mpi.org e-mail alias is gone... c'est la vie! -- Tim Mattox, Ph.D. - tmat...@gmail.com
