An interesting story on generational garbage collectors: a couple of versions ago, Lua experimented with a generational GC. But it didn't improve performance, so they kept the old incremental collector. A long time later, they looked at it more closely and realised that the actual problem was that the generational collector was moving objects out of the nursery too eagerly. Objects in the stack are live and will survive if the GC runs, but many of them will stop being live as soon as their function returns. They fixed the issue by making the stack objects that survive one round of GC to stay in the nursery. The new GC is now much faster than the old one, and is one of the big features of the upcoming Lua 5.4