That technique (commonly called semispace GC) works for mutable data as well, as long as you have a pointer indirection (so you can move), it's just less effici

That technique (commonly called semispace GC) works for mutable data as well, as long as you have a pointer indirection (so you can move), it's just less efficient than most others. It would be interesting to see whether the balance would shift significantly with immutable objects.