[eloff]

Yes, that's true, except for the calling into non-Lua libraries, this is where LuaJIT + ffi really shines. It can actually optimize away boxing/unboxing and inline the native function call into the trace (not the body of the native function, but the call itself.) Surely you're referring to something else? The often repeated wisdom on the LuaJIT mailing list is only use the Lua C API for legacy code as it can't come close to the performance or ease of use of the ffi. If your experience is otherwise, maybe the JIT bailed on your test code? The ffi is very slow without the JIT.

String and memory limitations have yet to bother me at all because anywhere speed matters you get order of magnitude improvements by managing the strings/memory yourself via the ffi. With Terra, it's clear that's the approach being advocated as well. I agree it really bolluxes small benchmarks, especially if the code is written for Lua and not done the "LuaJIT way" with the ffi. Outside of embedded or other exotic environments I think one would be hard-pressed to come up with a real-world workload where Lua PUC outperforms LuaJIT and there's no easy way to turn the tables. There are just far more options for optimization with LuaJIT and more ability to get closer to the metal than you have with Lua PUC.

None of that is to take away from what the Lua PUC guys have accomplished. Like any craftsmen who enjoys his work, I just like to use the best tools. That's LuaJIT in my opinion, and now Terra too.