[Python-Dev] Profile Guided Optimization active by-default

Stefan Behnel stefan_ml at behnel.de
Sat Aug 22 19:46:14 CEST 2015

Stefan Behnel schrieb am 22.08.2015 um 19:25:
> Guido van Rossum schrieb am 22.08.2015 um 18:55:
>> Regarding the training set, I agree that regrtest sounds to be better than
>> pybench. If we make this an opt-in change, we can experiment with different
>> training sets easily. (Also, I haven't seen the patch yet, but I presume
>> it's easy to use a different training set?
>> Experimentation should be encouraged.)
> A well chosen training set can have a notable impact on PGO compiled code
> in general, and switching from pybench to regrtests should make such a
> difference. However, since CPython's overall performance is mostly
> determined by the interpreter loop, general object operations (getattr!)
> and the basic builtin types, of which the regression test suite makes
> plenty of use, it is rather unlikely that other training sets would provide
> substantially better performance for Python code execution.

Note that this doesn't mean that it's a good workload for the C code in the
standard library (and I guess that's why Alecsandru initially excluded the
hashlib tests). Improvements on that front might still be possible. But
it's certainly a good workload for all the rest, i.e. for executing general
Python code.


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