[Python-Dev] opcode dispatch optimization (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Wed Dec 31 14:47:30 CET 2008

Hello,

I would like to mention that I've written a patch which enables "threaded interpretation" on the ceval loop with gcc (*). On my computer (an Athlon X2 3600+), it is good for a 15-20% speedup of the interpreter on pystone and pybench. I also had the opportunity to test it on a Core2-derived CPU, where it doesn't make a difference (I conjecture it's because Core2 CPUs have hardware-based indirect branch optimizations). It will make no difference if the interpreter is compiled with something else than gcc (I tested on Windows).

The additional complexity is very small. There's a separate script which is run to build the dispatch table (only if needed, that is if dis.py has been modified). In ceval.c, there are a couple of macros and some #ifdef's. That's all. It breaks no test in the regression suite.

Could other people test and report their results here? (the patch is for py3k, btw). Also, what are you thoughts for/against integrating this patch in the standard interpreter?

Regards

Antoine.

(*) please note: it has nothing to see with multithreading.

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