Why would you think it's not shared memory? Maybe I'm wrong here but by default Python's existing threading implementation uses shared memory. AFAIK we're just

Why would you think it's not shared memory? Maybe I'm wrong here but by default Python's existing threading implementation uses shared memory. AFAIK we're just talking about removing the global interpreter lock. I'm pretty sure the threading library uses system threads. So running without the GIL means actual parallelism across system threads with shared memory access.