On Wed, 15 Dec 2021 10:42:17 +0100 Christian Heimes <christ...@python.org> wrote: > On 14/12/2021 19.19, Eric Snow wrote: > > A while back I concluded that neither approach would work for us. The > > approach I had taken would have significant cache performance > > penalties in a per-interpreter GIL world. The approach that modifies > > Py_INCREF() has a significant performance penalty due to the extra > > branch on such a frequent operation. > > Would it be possible to write the Py_INCREF() and Py_DECREF() macros in > a way that does not depend on branching? For example we could use the > highest bit of the ref count as an immutable indicator and do something like > > ob_refcnt += !(ob_refcnt >> 63) > > instead of > > ob_refcnt++
Probably, but that would also issue spurious writes to immortal refcounts from different threads at once, so might end up worse performance-wise. Regards Antoine. _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/ILW5G6BS6754S4G7A7OUNFBNOAB7DNN2/ Code of Conduct: http://python.org/psf/codeofconduct/
