How to tweak Erlang VM configurations?

Question

I've read this Link on load testing eJabberd and MongooseIM. Author mentioned tweaking of Erlang VM Link.

Tweaks:

+K true
+A 5
+P 10000000
-env ERL_MAX_PORTS 1000000
-env ERL_FULLSWEEP_AFTER 2
-env ERL_MAX_ETS_TABLES 100000

I tried using them like that erl +K true specified in this Link.

Questions: How to tweak Erlang VM? How does one check if the setting has been set? Do i need restart eJabberd after changing the settings?

Answer 1

You should read the man page. Some of those switches have changed and you don't give them as -env variables more in newer Erlang VM's. ERL_MAX_PORTS is the +Q switch now, for instance.

Also, do you need tuning at all? What is the problem you are trying to solve by tweaking knobs? Forcing a large amount of processes with the +P flag takes up lots of memory on older Erlang releases. So unless you use that many processes, it is a bad move.

And yes, emulator flags need a restart for them to be effective.

Answer 2

What worked for me: There is config file for eJabberd - /etc/ejabberd/ejabberdctl.cfg where you can specify all this settings specifically for eJabberd. In this file you can configure options that are passed by ejabberdctl to the erlang runtime system when starting ejabberd