[Python-Dev] Linus on garbage collection (original) (raw)

Mark Shannon marks at dcs.gla.ac.uk
Fri May 6 16:46:08 CEST 2011

Neal Becker wrote:

http://gcc.gnu.org/ml/gcc/2002-08/msg00552.html Being famous does not necessarily make you right.

OS kernels are pretty atypical software, even if Linus is right about Linux, it doesn't apply to Python.

I have empirical evidence, not opinion, that PyPy and my own HotPy are a lot faster (x5 or better) on Unladen Swallow's gcbench benchmark (which stresses the memory management subsystem).

(Note that gcbench does not introduce any cycles, so its being easy on CPython)

In fact, for gcbench CPython spends over twice as long in the cycle-collector as HotPy takes in total! I don't have such detailed results for PyPy.

For other benchmarks, the HotPy GC times are often smaller than the inter-run variations in runtime, for example:

HotPy GC stats for pystones (on a slow machine with a small cache):

Total memory allocated: 20 Mbytes. 20 minor collections, 0 major collections Max heap size 2.4 Mbytes. Total time spent in GC: 3.5 milliseconds. ( <1% of execution time)

My GC is quick, but its not the fastest.

Evidence trumps opinion IMHO ;)

Cheers, Mark.

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