So I began implementing Lua into my 2D game engine and realized that it becomes increasingly difficult to run a script every update and a script every render while carrying over globals and not re-loading the script every time. What I mean by that is, I either have to load the script on EVERY update cycle and EVERY render cycle, OR I don't carry globals over by creating separate lua_State s. Any ideas, or am I just missing something HUGE with lua?

or am I just missing something HUGE with lua?

Imagine if in C, you decided to run an exe file every single Update/Render, rather than just calling a function.

You can do that in Lua - load the script once (just like we run an exe file once), and then call your Lua functions (from C) every time you want to update/render.

call your Lua functions (from C) every time you want to update/render.

I'd add one note about performance.

PIL book shows simple example using lua_getglobal(). It's quite costly due to lua string construction from passed C string.

It's few times cheaper to store required function in registry, and later retrieving that function by integer id, obtained during function registration.