Are there any caveats to it? I have a few questions related to it.

How costly is it to create more GILs? Is it any different from creating a separate python runtime? Once a new GIL is created, will it create everything (objects, variables, stack, heap) from scratch as required in that process or a copy of everything in the present heap and the stack is created? (Garbage collection would malfunction if they are working on same objects.) Are the pieces of code being executed also copied to new CPU cores? Also can i relate one GIL to one CPU core?

Now copying things is a fairly CPU intensive task (correct me if I am wrong), what would be the threshold to decide whether to go for multiprocessing?

PS: I am talking about CPython but please feel free to extend the answer to whatever you feel is necessary.