[Python-Dev] Experimenting with STM on CPython

Armin Rigo arigo at tunes.org
Wed Apr 11 14:51:34 CEST 2012

Hi Stefan,

On Wed, Apr 11, 2012 at 14:29, Stefan Behnel <stefan_ml at behnel.de> wrote:
>> Moreover the performance hit is well below 2x, more like 20%.
> Hmm, those 20% refer to STM, right? Without hardware support? Then hardware
> support could be expected to drop that even further?

Yes, that's using STM on my regular laptop.  How HTM would help
remains unclear at this point, because in this approach transactions
are typically rather large --- likely much larger than what the
first-generation HTM-capable processors will support next year.  But
20% looks good anyway :-)

> Did you do any experiments with running parallel code so far, to see if
> that scales as expected?

Yes, it scales very nicely on small non-conflicting examples.  I
believe that it scales just as nicely on large examples on CPython
too, based on the approach --- as long as we, as CPython developers,
make enough efforts to adapt a sufficiently large portion of the
CPython C code base (which would mean: most mutable built-in objects'

A bientôt,


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