[erlang-questions] The mystery of CPU utilization. Progress...

Convey Christian J NPRI ConveyCJ@REDACTED
Wed Mar 12 14:00:37 CET 2008

I guess this is more than an FYI than an actual question...

Earlier this week I asked some questions about what "-smp S n" does.  I was confused because even running a single Erlang process in non-smp mode caused both of my cores to light up.

In case anyone is interested, I have some more details.  Still baffling, but...

On my dual-core box, when run a single-process Erlang function, one CPU core runs at about 100% user load, and the other CPU core runs at about 100% *system* load.

On a quad-core box I have access to, I ran the same function concurrently, using between one and four Erlang processes.  As you'd expect, for each Erlang processes I had going, I pegged one CPU core at ~ 100% user load.  But unlike on my dual-core box, none of the quad-core's cores experienced any significant *system* load.

(One both computers I used the 'mpstat' program, with one instance of it monitoring each CPU core.)

Christian Convey
Scientist, Naval Undersea Warfare Centers
Newport, RI

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