[Beowulf] ...Re: Benchmark results

Rene Storm rene.storm at emplics.com
Tue Jan 6 18:00:18 EST 2004


HI,
first of all, thanks for the responses....

It seems that there are some more points I have to observe.
For example the hpl benchmark:
The job was running on two processors (smp) on loopback. Used time round about 20min. 
There was no cronjob, no X, only a niced top.
The machines environments are almost constant (temperature->lm_sensors).
A reboot after every single run.

And yes, the differences on the opterons are greater as on i386.
I will take a look at interleaving. But why should the memory allocation change between two runs?

So it seems, I will to go a little bit deeper into that and try to get some more results.
What I do expect is some sort of Gaussian distribution on the results.
I will take the hpl and throw the results into gnuplot.

One question about the walltime. Could this be a problem?
Does someone know how this really works? I read something about HZ and jiffies and so, but it was a bit confusing.
Maybe this could be the point were old, unfair heisenberg could have had a chance.

Rene Storm


-----Ursprüngliche Nachricht-----
Von: Michael Will [mailto:mwill at penguincomputing.com] 
Gesendet: Dienstag, 6. Januar 2004 18:53
An: beowulf at beowulf.org
Betreff: [Beowulf] Re: Benchmark results

Rene,

Do you see that fluctuation only on the opterons or also on the intel cpus
(I assume Xeon?)

If it was only on the opteron, then you will have node memory interleave
turned off in your bios, and sometimes the data you work with is close to
your CPU and sometimes far. (each CPU has a bank of RAM and accesses the
other CPUs bank through hypertransport, which is slower)

When running a memory and floatpoint intensive benchmark (neuronal network
training program like SNNS), we got two consistent results: They were
alternating, depending on which CPU the code ran, and they were 20% off of
each other for that setup.

Once we put in the same amount of memory in both banks, and turned on
'node memory interleave' in the bios, they were consistently between the
two, a bit closer to the faster value.

I will take a closer look at your CD later, too.

Michael Will
PS: Did I mention the opterons blew away the xeons by far?
-- 
Michael Will, Linux Sales Engineer
Tel:  415.358.2673  Toll Free:  888-PENGUIN
PENGUIN COMPUTING - The World's Most Reliable Linux System
www.penguincomputing.com


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