It would be great to run these tests. As we discussed, we should ignore for now that fact that a simple lock on each of the VCs is probably not entirely correct - however, it will give us some information on how much this approach might improve performance, at least on Breadboard. Bill On Jan 29, 2008, at 11:34 PM, Rajeev Thakur wrote:
Thanks for running the tests. I guess the next step, as we discussed at UIUC, would be to use a lock per vc instead of lock per process and see if that improves the message rate. (This simple change may not even work because some other data structures may need to be protected, but it is worth a try.)
Rajeev
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Pavan Balaji Sent: Tuesday, January 29, 2008 3:53 PM To: [email protected] Subject: [mpich2-core] MPICH2 Threading Overhead
Hi all,
I've run some experiments for the MPICH2 threading overhead on BG/P and Breadboard (test program is attached). I don't remember if IBM reported that the performance stays constant with increasing threads or if it degrades, but I'm noticing a drop in performance (results below).
On BG/P, this is slight yet noticeable, but on breadboard it's drastic. Note that 1 thread refers to "no extra threads" -- the main process does a self send/recv.
This is not the fairest comparison since MPICH2-BG/P is based on MPICH2-1.0.4p1, while the breadboard runs are on MPICH2-trunk. I'll try out MPICH2-1.0.4p1 on breadboard as well. But as a longer term solution I'm trying to get MPICH2-BG/P ported to MPICH2-trunk so that I can easily try out any threading enhancements that might go in to trunk from here on.
Thanks.
-- Pavan
-------------------------------------------------------------- -----------
BG/P: ---- # MPI Message Rate Test with 1 Threads # Size Latency (us) Message Rate (MMPS) 0 1.38 0.725 # MPI Message Rate Test with 2 Threads # Size Latency (us) Message Rate (MMPS) 0 3.59 0.557 # MPI Message Rate Test with 3 Threads # Size Latency (us) Message Rate (MMPS) 0 5.75 0.522 # MPI Message Rate Test with 4 Threads # Size Latency (us) Message Rate (MMPS) 0 7.93 0.504
Breadboard: ---------- # MPI Message Rate Test with 1 Threads # Size Latency (us) Message Rate (MMPS) 0 0.17 5.774 # MPI Message Rate Test with 2 Threads # Size Latency (us) Message Rate (MMPS) 0 1.69 1.180 # MPI Message Rate Test with 3 Threads # Size Latency (us) Message Rate (MMPS) 0 7.54 0.398 # MPI Message Rate Test with 4 Threads # Size Latency (us) Message Rate (MMPS) 0 2.04 1.963
-- Pavan Balaji http://www.mcs.anl.gov/~balaji
William Gropp Paul and Cynthia Saylor Professor of Computer Science University of Illinois Urbana-Champaign