[Beowulf] Re: dual core Opteron performance - re suse 9.3

Don Kinghorn kinghorn at pqs-chem.com
Tue Jul 12 08:36:15 PDT 2005

Hi Vincent,  ...all,

The code was built on a SuSE9.2 machine with gcc/g77 3.3.4. The same 
executable was run on both systems.

Kernel for the 2 dual-node setup was SuSE stock 2.6.8-24-smp
for the 9.3 setup with the dual-core cpus it was the stock install kernel

Memory was fully populated on the 2 node setup -- 4 one GB modules per board, 
there are only 4 slots on the Tyan 2875 (I had mistakenly reported yesterday 
that there was only 2GB/per board for the benchmark numbers)
The dual-core system had 4 one GB modules arranged 2 for each cpu.

Important(?) bios settings were;

Bank interleaving "Auto"
Node interleaving "Auto"
PowerNow "Disable"
MemoryHole "Disabled" for both hardware and software settings

The speedup we saw on the dual-core was less than 10% for the most jobs. MP2 
jobs with heavy i/o (worst case) was around a %20 hit (there were twice as 
many processes hitting the raid scratch space at the same time)

I still have lots of testing and tuning to do. These tests were just to see if 
was going to work and how much trouble it was going to be. ( It was a LOT of 
trouble getting SuSE9.3 installed but I think worth it in the end)

Best to all

> If you 'did get better performance', that's possibly because
> you have some kernel 2.6.x now, allowing NUMA, and a new
> compiler version of gcc like 4.0.1 that has been bugfixed more than
> the very buggy series 3.3.x and 3.4.x
> Can you show us the differences between the compiler versions and kernel
> versions you had and whether it's NUMA?
> Also how is your memory banks configured, for 64 bits usage or 128 bits
> single cpu usage, or are all banks filled up?

Dr. Donald B. Kinghorn Parallel Quantum Solutions LLC

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