Why Erlang is suitable for soft real-time applications, but not for hard real-time?

Question

Or maybe it's good for hard real-time too?

Answer 1

Garbage collection can lead to pauses of unpredictable duration; as such, you can't put hard upper bounds on latency. The definition of hard real time is basically that you can set hard bounds on latency, so this is a problem.

Answer 2

Oh, nobody has answered why it is good for soft realtime though:

In Erlang, each process has its own garbage collector. So if the processes each are kept with a rather small heap, then GC pauses tend to be very small and this gives a really good realtime behaviour.

Answer 3

There is a presentation from 2008 by Vincenzo Nicosia describing work on HRT erlang (HARTE), which also describes the problems regarding hard real-time of the current BEAM, etc. Have a look at http://www.erlang.org/workshop/2007/proceedings/05nicosi.pdf