[Beowulf] Ammasso based clusters

[Dow Hurst DPHURST]

Are there any Ammasso based clusters out there that someone has some
experience with tuning the Ammasso communication parameters for the RDMA
interfaces?  We have a small cluster with Ammasso interconnects running
NAMD 2.6b1.  The defaults for Ammasso communication are what we use for
each NAMD job.  I'd like to know if changing those such as:

VIADEV_NUM_RDMA_BUFFERS
VIADEV_MAX_RENDEZVOUS

would be worth trying.  I'm hoping someone might have already done some
tuning and has some advice.  The typical job now is using 16 CPUs thru 8
interconnects.  Ramping up the number nodes tends to improve performance up
to 20 CPUs but flattens after that til we get to 32 CPUs.  Each node is a
dual Opteron with a single Ammasso card.  The rack has a non-blocking gig-e
SMC 8624 switch.
Thanks,
Dow

__________________________________
Dow P. Hurst, Research Scientist
Department of Chemistry and Biochemistry
University of North Carolina at Greensboro
435 New Science Bldg.Greensboro, NC 27402-6170