[the_why_of_y]

It doesn't actually implement concurrent GC, although what it does implement is far simpler and has a similar effect (low latencies) as concurrent GC.

Each Erlang process has a separate heap that is collected independently; because the process heap is usually small a stop-the-process collection does not take much time.

The downside is that sending messages between processes requires copying all the data that is sent between process heaps.