Comment by fsfod
2 hours ago
I think it was more the extra layers of indirection added to function environment\effectively global variable access added in 5.2 .
The removal of scanning for changed userdata finalizer meta method in 5.2 is just a commonsense fix for bad design that made GC atomic phase run time, thats not incremental scale up with the number of GC userdata objects alive no matter if they have a finalizer or not.
5.1 had function environments, then 5.2 changed them from a hidden value to a hardcoded variable name that was easier to change. How did that add extra indirection or slow anything down?