[erlang-questions] logical_processors_available unknown on mac

Jesper Louis Andersen <>
Wed Feb 17 16:32:25 CET 2016


On Wed, Feb 17, 2016 at 1:25 PM, Alin Popa <> wrote:

> I was recently trying to use
> `erlang:system_info(logical_processors_available).` on my mac, and getting
> `unknown` atom back; anyone has any idea if this is really by design?
>

A bit of guesswork here, and someone will correct my mistakes I'm sure:

You can't take your core off-line in OSX and replace it while the system is
running to the best of my knowledge. So you may not be able to query this
information from the kernel at all. Illumos/Solaris has support for this
for instance, and I guess this is why there is an entry for it.

If your Solaris server has a failing CPU package, you can take it offline
from the OS, replace it, and start the new CPU package, without stopping
the system. When this happens, you might have fewer logical processors
available in the system for some reason.

Many of the settings regarding CPUs are not that supported on OSX. Another
such call is the +sbt option, which you can't use on OSX since there is no
way to bind threads to CPU cores.


-- 
J.
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