Yes (although so far only in this branch of PyPy). It basically uses fine-grained locking instead of a global lock. I can't explain it simply so I'll just point to recent discussion: https://news.ycombinator.com/item?id=3941642 and https://news.ycombinator.com/item?id=3464484 and the beginning of this project https://news.ycombinator.com/item?id=2710235