GeezerVison is showing github.com — Add a mechanism to disable the GIL · Issue #116167 · python/cpython
Add a mechanism to disable the GIL #116167DescriptionFeature or enhancement
Proposal:
PYTHON_GIL=0 python ... or python -Xgil=0 ... should disable the GIL at runtime, in Py_GIL_DISABLED builds. This will be similar in spirit to colesbury/nogil-3.12@f546dbf16a.
Has this already been discussed elsewhere?
I have already discussed this feature proposal on Discourse
Links to previous discussion of this feature:
https://peps.python.org/pep-0703/
Linked PRs
Activityitamaro commented on Feb 29, 2024 shouldn't the GIL be disabled by default in free-threading builds? (and then have -x withgil or PYTHON_GIL=1 to enable it) swtaarrs commented on Feb 29, 2024 @colesbury probably has more thoughts, but I believe we're expecting disabling the GIL to be pretty buggy initially. So even if we're targeting disabling the GIL by default in 3.13, we'll probably want the GIL to stay on by default for a while first. Reacted by Dielson Sales, Yahya Jabary and Dmitry colesbury commented on Feb 29, 2024 I think we want to work towards the behavior described in PEP 703 with the Py_mod_gil slot and PTYHONGIL 1 environment variable: https://peps.python.org/pep-0703/#py-mod-gil-slot.
As a starting point:
- We should keep the GIL enabled by default in free-threaded builds (as it is currently is) for now.
PYTHON_GIL=0 should disable the GIL
We can add the Py_mod_gil slot and eventually disable the GIL by default later on, but hopefully still before the 3.13 release.
EDIT: There seemed to be a strong preference for UNDERSCORES_IN_NAMES in https://discuss.python.org/t/change-environment-variable-style/35180
Footnotes
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Or PYTHON_GIL -- I think people have expressed a preference for _ separated names in new environment variables ↩
Reacted by Itamar Oren, Brett Simmers, Erlend E. Aasland, Sergio Castillo and Kerim Kabirov jakirkham commented on Mar 12, 2024 The PEP references PYTHONGIL whereas PR ( #116338 ) adds PYTHON_GIL
Is there a difference between these two? Or is there a plan to consolidate to with or without _?
Sorry I know this is a minor question, but want to help avoid potential confusion down the road itamaro commented on Mar 12, 2024
The PEP references PYTHONGIL whereas PR ( #116338 ) adds PYTHON_GIL
Is there a difference between these two? Or is there a plan to consolidate to with or without _?
there's no difference - underscored env vars is the current preference among core devs (discussion & poll)
the implementation & documentation are the source of truth, and may differ from the PEP in some ways. Reacted by jakirkham and Brett Simmers gvanrossum commented on Mar 13, 2024 IIUC the python binaries distributed for Mac and Windows on python.org for 3.13 will not be built with --disable-gil, right? And IIUC we intend for Linux distros also to have binaries named python3.13, python3 and possibly python that are built without that flag, giving the option to also distribute binaries built with --disable-gil under different names. So this env var only applies to the latter, right? (For 3.14 the situation may be different.) colesbury commented on Mar 13, 2024 The environment variable PYTHON_GIL and -X gil=0 option only apply to the free-threaded binaries. Setting them with the default build cause an error on startup 1.
The Windows installer can optionally also install the free-threaded executable python3.13t.exe along with the default (with GIL) 3.13 executable. The Windows embeddable package only contains the default build (no free-threaded binaries).
Example Windows installation
Directory: C:\Users\coles\AppData\Local\Programs\Python\Python313
Mode LastWriteTime Length Name
---- ------------- ------ ----
d----- 3/13/2024 2:30 PM DLLs
d----- 3/13/2024 2:30 PM Doc
d----- 3/13/2024 2:30 PM include
d----- 3/13/2024 2:30 PM Lib
d----- 3/13/2024 2:30 PM libs
d----- 3/13/2024 2:30 PM Scripts
d----- 3/13/2024 2:30 PM tcl
-a---- 3/12/2024 10:10 PM 33861 LICENSE.txt
-a---- 3/12/2024 10:12 PM 1841840 NEWS.txt
-a---- 3/12/2024 10:10 PM 103192 python.exe
-a---- 3/12/2024 10:11 PM 103192 python3.13t.exe
-a---- 3/12/2024 10:10 PM 69912 python3.dll
-a---- 3/12/2024 10:10 PM 6829336 python313.dll
-a---- 3/12/2024 10:11 PM 6903064 python313t.dll
-a---- 3/12/2024 10:11 PM 70936 python3t.dll
-a---- 3/12/2024 10:10 PM 101656 pythonw.exe
-a---- 3/12/2024 10:11 PM 101656 pythonw3.13t.exe
-a---- 3/12/2024 10:10 PM 119192 vcruntime140.dll
-a---- 3/12/2024 10:10 PM 49528 vcruntime140_1.dll
The macOS installer does not currently support installing the free-threaded build. I'm not sure what the plan is for 3.13.
Your summary of the Linux situation matches my understanding.
Footnotes
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We may want to improve the error message. It's currently:
Fatal Python error: config_read_gil: PYTHON_GIL / -X gil are not supported by this build
Python runtime state: preinitialized ↩
Reacted by Brett Simmers and Кирилл swtaarrs commented on Mar 13, 2024 Once gh-116749 is complete, we can start running tests in CI with the GIL disabled using one of these flags (or by doing gh-116329).
This is finished unless someone wants to keep it open to track improving the error message (from Sam's last comment).
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