As stated at the conf call, I did some performance testing on a 32 cores
So, here is graph showing 500 timings of an allreduce operation (repeated
15,000 times for good timing) with sysv, mmap on /dev/shm and mmap on
What is shows :
- sysv has the better performance ;
- having the mmap file in /dev/shm is very close to sysv. We only have
+0.1 us for a complete allreduce operation, but it seems stable. The noise
is identical to sysv (must be OS noise) ;
- having the mmap file in /tmp (ext3) decreases performance (+0.4 us
compared to /dev/shm) and seems prone to some "other" noise.
Warning : the graph does not start at 0.
On Tue, 27 Apr 2010, Samuel K. Gutierrez wrote:
> With Jeff and Ralph's help, I have completed a System V shared memory
> component for Open MPI. I have conducted some preliminary tests on our
> systems, but would like to get test results from a broader audience.
> As it stands, mmap is the defaul, but System V shared memory can be activated
> using: -mca mpi_common_sm sysv
> Input is greatly appreciated!
> Samuel K. Gutierrez
> Los Alamos National Laboratory
> devel mailing list