[mpich-discuss] MPICH2-1.0.8 performance issues on Opteron Cluster

James S Perrin james.s.perrin at manchester.ac.uk
Mon Jan 5 08:00:43 CST 2009

	I thought I'd just mention that I too have found that our software 
performs poorly with nemesis compared to ssm on our multi-core machines. 
I've tried it on both a 2xDual core AMD x64 and 2xQuad core Xeon x64 
machines. It's roughly 30% slower. I've not been able to do any analysis 
as yet as to where the nemesis version is loosing out?

	The software performs mainly point-to-point communication in a master 
and slaves model. As the software is interactive the slaves call 
MPI_Iprobe while waiting for commands. Having compiled against the ssm 
version would have no effect, would it?


Sarat Sreepathi wrote:
> Hello,
> We got a new 10-node Opteron cluster in our research group. Each node 
> has two quad core Opterons. I installed MPICH2-1.0.8 with Pathscale(3.2) 
> compilers and three device configurations (nemesis,ssm,sock). I built 
> and tested using the Linpack(HPL) benchmark with ACML 4.2 BLAS library 
> for the three different device configurations.
> I observed some unexpected results as the 'nemesis' configuration gave 
> the worst performance. For the same problem parameters, the 'sock' 
> version was faster and the 'ssm' version hangs. For further analysis, I 
> obtained screenshots from the Ganglia monitoring tool for the three 
> different runs. As you can see from the attached screenshots, the 
> 'nemesis' version is consuming more 'system cpu' according to Ganglia. 
> The 'ssm' version fares slightly better but it hangs towards the end.
> I may be missing something trivial here but can anyone account for this 
> discrepancy? Isn't 'nemesis' device or 'ssm' device recommended for this 
> cluster configuration? Your help is greatly appreciated.

   James S. Perrin

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