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| -rw-r--r-- | Doc/whatsnew/3.13.rst | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/Doc/whatsnew/3.13.rst b/Doc/whatsnew/3.13.rst index c82d8bd..df38a61 100644 --- a/Doc/whatsnew/3.13.rst +++ b/Doc/whatsnew/3.13.rst @@ -99,6 +99,12 @@ New typing features: * :pep:`742`: :data:`typing.TypeIs` was added, providing more intuitive type narrowing behavior. +Free-threading: + +* :pep:`703`: CPython 3.13 has experimental support for running with the + :term:`global interpreter lock` disabled when built with ``--disable-gil``. + See :ref:`Free-threaded CPython <free-threaded-cpython>` for more details. + New Features ============ @@ -1052,6 +1058,46 @@ See :pep:`744` for more details. Tier 2 IR by Mark Shannon and Guido van Rossum. Tier 2 optimizer by Ken Jin.) +.. _free-threaded-cpython: + +Free-threaded CPython +===================== + +CPython will run with the :term:`global interpreter lock` (GIL) disabled when +configured using the ``--disable-gil`` option at build time. This is an +experimental feature and therefore isn't used by default. Users need to +either compile their own interpreter, or install one of the experimental +builds that are marked as *free-threaded*. + +Free-threaded execution allows for full utilization of the available +processing power by running threads in parallel on available CPU cores. +While not all software will benefit from this automatically, programs +designed with threading in mind will run faster on multicore hardware. + +Work is still ongoing: expect some bugs and a substantial single-threaded +performance hit. + +The free-threaded build still supports optionally running with GIL enabled at +runtime using the environment variable :envvar:`PYTHON_GIL` or the command line +option :option:`-X gil`. + +* Use :func:`!sys._is_gil_enabled` to determine if the :term:`GIL` is enabled. + +* Use ``sysconfig.get_config_var("Py_GIL_DISABLED")`` to identify CPython + builds configured with ``--disable-gil``. + +C-API extensions need to be built specifically for the free-threaded build. + +* Extensions that support running with the :term:`GIL` disabled should use + the :c:data:`Py_mod_gil` slot. Extensions using single-phase init should use + :c:func:`PyUnstable_Module_SetGIL` to indicate whether they support running + with the GIL disabled. Importing C extensions that don't use these mechanisms + will cause the GIL to be enabled unless the GIL was explicitly disabled with + the :envvar:`PYTHON_GIL` environment variable or the :option:`-X gil=0` + option. + +* pip 24.1b1 or newer is required to install packages with C extensions in the + free-threaded build. Deprecated |