[Cython] Can we remove the FastGIL implementation?

[Lisandro Dalcin]

Disclaimer: I may be doing something wrong, I did not put a lot of effort
into it.
With the microbenchmark that was offered in the GH issue, I see little
difference.
Use the attached zip file to reproduce yourself.
Change tox.ini to "cython<3" to try 0.29.x.
BTW, in the 0.29.x case, I see no compilation error as claimed in the GH
issue.

$ ./run.sh
CFLAGS=-g0 -Ofast -DCYTHON_FAST_GIL=0
Running test_gil_already_held ... took 0.08735537528991699
Running test_gil_released     ... took 0.6329536437988281
py37: OK ✔ in 3.57 seconds
Running test_gil_already_held ... took 0.09007453918457031
Running test_gil_released     ... took 0.4598276615142822
py38: OK ✔ in 3.19 seconds
Running test_gil_already_held ... took 0.10935306549072266
Running test_gil_released     ... took 0.4512367248535156
py39: OK ✔ in 3.25 seconds
Running test_gil_already_held ... took 0.09970474243164062
Running test_gil_released     ... took 0.46637773513793945
py310: OK ✔ in 3.21 seconds
Running test_gil_already_held ... took 0.08569073677062988
Running test_gil_released     ... took 0.46811795234680176
py311: OK ✔ in 3.22 seconds
Running test_gil_already_held ... took 0.15221118927001953
Running test_gil_released     ... took 0.2246694564819336
  py37: OK (3.57 seconds)
  py38: OK (3.19 seconds)
  py39: OK (3.25 seconds)
  py310: OK (3.21 seconds)
  py311: OK (3.22 seconds)
  pypy3.9: OK (5.24 seconds)
  congratulations :) (21.71 seconds)
CFLAGS=-g0 -Ofast -DCYTHON_FAST_GIL=1
Running test_gil_already_held ... took 0.08835673332214355
Running test_gil_released     ... took 0.6265637874603271
py37: OK ✔ in 1.42 seconds
Running test_gil_already_held ... took 0.09030938148498535
Running test_gil_released     ... took 0.456279993057251
py38: OK ✔ in 1.17 seconds
Running test_gil_already_held ... took 0.10986089706420898
Running test_gil_released     ... took 0.45894527435302734
py39: OK ✔ in 1.2 seconds
Running test_gil_already_held ... took 0.10107588768005371
Running test_gil_released     ... took 0.5052204132080078
py310: OK ✔ in 1.21 seconds
Running test_gil_already_held ... took 0.08566665649414062
Running test_gil_released     ... took 0.4581136703491211
py311: OK ✔ in 1.13 seconds
Running test_gil_already_held ... took 0.15286779403686523
Running test_gil_released     ... took 0.22533607482910156
  py37: OK (1.42 seconds)
  py38: OK (1.17 seconds)
  py39: OK (1.20 seconds)
  py310: OK (1.21 seconds)
  py311: OK (1.13 seconds)
  pypy3.9: OK (1.64 seconds)
  congratulations :) (7.81 seconds)


On Tue, 19 Sept 2023 at 10:09, Stefan Behnel <stefan_ml at behnel.de> wrote:

> Hi,
>
> I've seen reports that Cython's "FastGIL" implementation (which basically
> keeps the GIL state in a thread-local variable) is no longer faster than
> CPython's plain GIL implementation in recent Python 3.x versions.
> Potentially even slower. See the report in
>
> https://github.com/cython/cython/issues/5703
>
> It would be helpful to get user feedback on this.
>
> If you have GIL-heavy Cython code, especially with nested
> with-nogil/with-gil sections across functions, and a benchmark that
> exercises it, could you please run the benchmark with and without the
> feature enabled and report the results?
>
> You can add "-DCYTHON_FAST_GIL=0" to your CFLAGS to disabled it (and "=1"
> to enable it explicitly). It's enabled by default in CPython 3.6-3.11 (but
> disabled in Cython 0.29.x on Python 3.11).
>
> Thanks,
> Stefan
> _______________________________________________
> cython-devel mailing list
> cython-devel at python.org
> https://mail.python.org/mailman/listinfo/cython-devel
>


-- 
Lisandro Dalcin
============
Senior Research Scientist
Extreme Computing Research Center (ECRC)
King Abdullah University of Science and Technology (KAUST)
http://ecrc.kaust.edu.sa/
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