Optimizing the BEAM's scheduler for many-core machines

The BEAM is famous for supporting many lightweight processes. But the scheduler responsible for deciding which of these processes should execute on which core at which time was designed at a time when most servers only had a few cores, and can suffer from severe lock contention issues when used on many-core machines (100+ cores). In this talk I’ll explain the main ideas behind how the BEAM’s scheduler works, how to discover and investigate lock-contention issues, and then explain some recent changes that mitigated these issues for the BEAM’s scheduler.

Key Takeaways:

The general design of the BEAM’s scheduler (task-stealing, periodic rebalancing with immigration/emigration between runqueues) How to use lock-counting and interpret its results If you have performance issues on large servers, upgrade to the latest OTP for a large improvement

Target Audience:

Anyone curious about the BEAM’s internals, anyone struggling to improve the scalability of their Erlang/Elixir application on a many-core server.