[Python-Dev] Python 2.6a2 execution times with various compilers

Gregory P. Smith greg at krypto.org
Sun Apr 13 00:21:32 CEST 2008


On Sat, Apr 12, 2008 at 11:09 AM, Jeroen Ruigrok van der Werven <
asmodai at in-nomine.org> wrote:

> I did some more tests concentrating on GCC, partly based on the feedback I
> got, results at
> http://www.in-nomine.org/2008/04/12/python-26-compiler-options-results/
>
> Executive summary: Python needs to be compiled with -O2 or -O3. Not doing
> so, no optimization level, results with GCC 4.2.1 in a doubling of
> execution
> time. Using just -O1 is still ~15% slower than using -O2.
>
> Using -mtune=native -march=native can shave of 0,1/0,2 seconds, but
> otherwise I did not find much difference in using having march or mfpmath
> present.
>
> Profile-guided optimization did not help much, as might be expected, it
> pushed about the same kind of optimization as the mtune/march combination.
>

With gcc 4.1.3 i'm finding that profile guided optimization when trained on
pybench or regrtest does make a measurable difference (2-5% overall time
with 10-20% on some pybench tests).  I haven't run benchmarks enough times
to be confident in my results yet, I'll report back with data once I have
it.  I'm testing both pybench and regrtest as profiling training runs.

I will check in a special makefile target for easy gcc profile guided
compiles shortly so that those who want faster builds easily produce them.
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