da-woods schrieb am 19.09.23 um 21:38:
I think the detail that was missing is you need to add the `#cython:
fast_gil = True` to enable it.
[...]
So my conclusion is that from 3.11 onwards Python sped up their own GIL
handling to about the same as we used to have, and fastgil has turned into
a pessimization.
I tried the benchmark with the master branch on my side again, this time
with correct configuration. :)
Turns out that enabling the FastGIL feature makes it much slower for me (on
Ubuntu Linux 20.04) in both Py3.8 and 3.10:
"""
* Python 3.10 (-DCYTHON_FAST_GIL=0)
Running the test (already held)...
took 1.2482502460479736
Running the test (released)...
took 6.444956541061401
Running the test (already held)...
took 1.2358744144439697
Running the test (released)...
took 6.4064109325408936
* Python 3.10 (-DCYTHON_FAST_GIL=1)
Running the test (already held)...
took 2.243091583251953
Running the test (released)...
took 7.32707667350769
Running the test (already held)...
took 2.4065449237823486
Running the test (released)...
took 7.50264573097229
"""
I also tried it with PGO enabled and got more or less the same result. The
Python installations that I tried it with were both PGO builds.
It's probably mixed across platforms, different configurations and C
compilers. I looked through the "What's new" document for Py3.10 and 3.11
but couldn't find mentions of GIL improvements. Just that some other things
have become faster.
So – disable the feature in Python 3.11 and later? (Currently it's disabled
in 3.12+.)
Py3.11+ would suggest that we keep the code in Cython 3.1, since that will
support older Python versions that still seem to benefit from it.
Stefan
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