[Rochus]

> tracking down unexpected performance regressions is more work

In particular you have to know a lot of technical details about LuaJIT, which essentially contradicts the benefit of using Lua in the first place. In my case I used LuaJIT as a backend, directly generating bytecode considering LuaJIT internals as far as possible. But it's still much slower than e.g. Mono.

> your luajit results suggest that typically a c subroutine (and perhaps consequently a pallene subroutine) will enjoy a 4× speed advantage

The Lua implementation of Are-we-fast-yet apparently doesn't consider LuaJIT internals, but is just pretty ideomatic Lua not optimized for speed. So it doesn't represent what is possible with LuaJIT performance-wise, but gives a good impression how LuaJIT performs in general applications.