Autotuning of the number of async I/O threads

[michaelklishin]

See this mailing list thread.

I wonder if we can do autotuning that will work reasonably well on all supported platforms.

[binarin]

So is default value like 16 * erlang:system_info(logical_processors_available) good enough?

[michaelklishin]

@binarin that sounds good but I'd add "but no fewer than 64".

[binarin]

Looks like detecting number of CPUs is not as simple as it seems on some OSes. Lev Walkin posted the following snippet in erlang-russian ML:

ncpus() ->
    case erlang:system_info(logical_processors_available) of
        unknown -> % Happens on Mac OS X.
            erlang:system_info(schedulers);
        N -> N
    end.

[michaelklishin]

@binarin combined with the "no fewer than 64" condition above, it sounds good to me. It's unlikely that there will be significantly more schedulers configured than there are logical cores. We might want to cap the maximum number, say, at 512 or 1024, too.