[@haypo]
> http://python.dzone.com/articles/diagnosing-memory-leaks-python
> Great job! Using mmap() for arenas is the best solution for this issue.

?  I read the article, and they stopped when they found "there seemed to be a ton of tiny little objects around, like integers.".  Ints aren't allocated from arenas to begin wtih - they have their own (immortal & unbounded) free list in Python2.  No change to pymalloc could make any difference to that.