[KMag]

I'm talking about generational non-copying collectors (possible, but certainly not common). Examples of non-generational collectors are non sequitur. You're talking the diagonally opposite corner of the square diagram. (What's the name of those 4-part square diagrams? I forget the name of the guy they're named after.)

For instance, you could have a mark-and-sweep collector that would mark everything and then first sweep just the most recently created arena, and only do a full sweep if not enough space was freed. It wouldn't be perfectly generational unless it was also compacting, but the youngest arena might be a decent heuristic. Or, for the cost of one pointer in every object header, the GC could keep a singly linked list of the youngest generation.

I don't think it's a great idea, but you can do a non-moving generational GC if you want to interact with C/C++ without forcing pinning/un-pinning of objects (or forcing C/C++ to only interact with GC'd objects via pinned handles).