[bdarnell]

PyPy has higher memory usage than CPython for two main reasons: A) JIT-generated code, B) pure garbage collection lets dead objects live longer than CPython's refcount/GC hybrid. Neither of these is going to go away, although it's reasonable to expect the gap to narrow over time. More importantly, much of this extra memory is a fixed cost, so while simple programs will see a 10x increase, real-world programs should see a less dramatic impact.

FWIW, my own tests of pypy 1.7 have shown the memory overhead to be about 3x: http://groups.google.com/group/python-tornado/browse_thread/...