Sam Gross worked on this, this made rounds recently in Python user world: https://docs.google.com/document/d/18CXhDb1ygxg-YXNBJNzfzZsDFosB5e6BfnXLlejd9l0/edit h

Sam Gross worked on this, this made rounds recently in Python user world: https://docs.google.com/document/d/18CXhDb1ygxg-YXNBJNzfzZsDFosB5e6BfnXLlejd9l0/edit https://docs.google.com/document/d/18CXhDb1ygxg-YXNBJNzfzZsD... It's a fork of Python 3.9, takes out GIL and introduces optimisations to speed up both single- and multi-threaded execution (since the bar set by PSF is that no-GIL implementations must be at least as fast as GIL single threaded programs). He ends up with a net 10% speed improvement. If he does these optimisations, and also doesn't remove the GIL, the performance boost is even larger. So, depending on how you look at it, it's either: - A bunch of optimisations, plus a GILectomy which slows Python down, or - A bulk change that removes GIL and speeds things up Since these improvements were in a similar ballpark, my fear was that the improvements are taken off the branch, with GIL left in place...