[kwlug-disc] benchmark: performance on six cores = 1 on one core = 6

John Van Ostrand john at netdirect.ca
Wed Jun 2 20:52:45 EDT 2010

----- Original Message -----
> Not that surprising. Modern CPU cores are the fastest component in a
> system - by an order of magnitude. Once you get outside of the L2
> cache, performance takes a big hit. If a job will fit in one core
> +on-die memory, it will run much faster than the same job spread over
> several fractionally used cores.
> Too bad the whole internet does not yet fit in a single CPU core. If
> it did, then his test program would model actual usage.
> And for high-performance couputing, turn off the hyperthreading. It
> just confuses things.

I would have thought that affinity algorithms would have made a process prefer the same core and so context switching would be insignificant.

Another factor is that some new CPUs can overclock one core if the other cores are unused. I think this might have been a BIOS setting rather than a run-time decision.

John Van Ostrand 
CTO, co-CEO 
Net Direct Inc. 
564 Weber St. N. Unit 12, Waterloo, ON N2L 5C6 
Ph: 866-883-1172 x5102 
Fx: 519-883-8533 

Linux Solutions / IBM Hardware 

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