[erlang-questions] My frustration with Erlang

[Jan Lehnardt]

On Sep 12, 2008, at 17:00, Paul Fisher wrote:
> Can anyone with experiences running a sufficiently complex system on  
> 8+
> core systems share your experiences?  I would love to hear from  
> someone
> intimate with the SMP implementation on the state of affairs and
> possible future directions.

I don't claim any experience in this field but I did a few tests with  
CouchDB
on a 32 core machine. I've seen linear performance increase up to 14  
cores
with a CPU utilisation of ~22% and no disk I/O (makes sense, little  
data, loads
of RAM). I tested with increasing +S parameters for `erl`. We ran the  
results
by some friends at Sun who suggested that this might be a bottleneck  
in the
networking layer. Something might have a per-CPU (not per-core)  
bottleneck.
Some kernel tuning in Solaris and possibly better NIC-programming  
could solve
this one, but I only had access to the box for a short time and had no  
chance
to change any boot-parameters, let alone hardware specs. Profiling  
showed that
Erlang was mostly waiting for network I/O which further underlines the  
Solaris
config problem theory.

Cheers
Jan
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