> "biased reference counts" and is described in this paper by Jiho Choi et al. With this scheme, the reference count in each object is split in two, with one "l

> "biased reference counts" and is described in this paper by Jiho Choi et al. With this scheme, the reference count in each object is split in two, with one "local" count for the owner (creator) of the object and a shared count for all other threads > The interpreter's memory allocator has been replaced with mimalloc These are very similar ideas! Mimalloc is notable for its use of separate local and remote free lists, where objects that are being freed from a different thread than the page’s heap’s owner are placed in a separate queue. The local free list is (IIRC) non-atomic until it is empty and local allocs start pulling from the remote queue. The general idea is clearly lazy support for concurrency, matching up perfectly with Python’s need to keep any single threaded perf it has. I’m impressed with the application of all of these things at once.