世代別GCは、今実装してるっぽい？
どの辺が、"some internal modifications"なんだろ？

http://lua-users.org/lists/lua-l/2002-10/msg00191.html

> what is the current plan for GC in Lua 5 [...]

We are planning to release 5.0, and then to start working in a
generational GC for 5.1. To make a new GC for 5.0 would delay too much
its final release.

-- Roberto

http://lua-users.org/lists/lua-l/2003-01/msg00147.html

>"incremental garbage collection"? Are there plans for an incremental
>collector or is the generational one being summerised (wrongly?) as an
>incremental one? Did I miss something?

You read it right, we plan to have incremental garbage collection in 5.1.
Lua 5.0 already has some internal modifications to allow this but the real
work will begin as soon as Lua 5.0 (final) is released officially.
--lhf