Erlang on the niagara

David Hopwood <>
Thu Jun 8 19:01:23 CEST 2006


Joe Armstrong (AL/EAB) wrote:
> The results were as follows:
> 
> 	#CPUs   Speedup
> 	1	0,953
> 	2	1,855
> 	3	2,679
> 	4	3,44
> 	5	4,012
> 	6	4,624
> 	7	5,093
> 	8	5,46
> 	9	5,73
> 	10	6,11
> 	11	6,108
> 	12	6,47
> 	13	6,58
> 	14	6,8
> 	15	6,67
> 	16	7
[...]

That's not too shabby, for a single-line change.

> Why can't we speed up beyond a factor 7 - who knows? - at some stage
> things do get serialised, there is after all only one disk on the
> machine, and the SMP erlang has to serialise all disk I/O, even if the
> programs generating data run in parallel, [...]

Do you mean that it does disk I/O in a single OS thread, or with a mutex
around the I/O code, or just that the I/O is serialized at the hardware
bus level?

-- 
David Hopwood <>





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