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Sep 25, 2024
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gh-124370: Add "howto" for free-threaded Python #124371

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gh-124370: Add "howto" for free-threaded Python
colesbury Jun 21, 2024
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Update Doc/howto/free-threading-python.rst
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interned -> immortalized
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colesbury Sep 24, 2024
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Co-authored-by: Carol Willing <carolcode@willingconsulting.com>
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@colesbury @willingc
colesbury and willingc authored Sep 24, 2024
commit 91ec1cae09cd3c94be13d8e52a212b2f62ffb718
12 changes: 6 additions & 6 deletions Doc/howto/free-threading-python.rst
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Expand Up @@ -4,9 +4,8 @@
Python experimental support for free threading
**********************************************

Starting with the 3.13 release, CPython has experimental support for running
with the :term:`global interpreter lock` (GIL) disabled in a build of Python
called :term:`free threading`. This document describes the implications of
Starting with the 3.13 release, CPython has experimental support for a build of Python
called :term:`free threading` where the :term:`global interpreter lock` (GIL) is disabled. This document describes the implications of
free threading for Python code. See :ref:`freethreading-extensions-howto` for
information on how to write C extensions that support the free-threaded build.
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We seem to switch between "free threading" and "free-threaded" kind of randomly. I can't decide if this is OK or if we should choose one and stick with it.

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I think it's fine. We also say both "multithreaded" and "multithreading" depending on the context.


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I wonder if we could add a quick snapshot of the overall plan: if everything works out, eventually free threading will be the only build, etc. Also, maybe a statement about how most programmer won't need to be concerned with this, we're doing a lot to keep everyday Python programs behaving the same, etc.

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I would perhaps add a note in the seealso block that refers to the PEP and adds 1 or 2 highlights:

  • performance conscious users may wish to try the free threaded version
  • most users can safely continue to use the default CPython version
  • when free threading is no longer experimental, the versions will converge into one version for all.

Expand Down Expand Up @@ -52,12 +51,12 @@ Thread safety
=============

The free-threaded build of CPython aims to provide similar thread-safety
behavior at the Python level to the GIL-enabled build. Built-in
behavior at the Python level to the default GIL-enabled build. Built-in
types like :class:`dict`, :class:`list`, and :class:`set` use internal locks
to protect against concurrent modifications in ways that behave similarly to
the GIL. However, Python has not historically guaranteed specific behavior for
concurrent modifications to these built-in types, so this should be treated
as a description of the current implementation, not a guarantee of future
as a description of the current implementation, not a guarantee of current or future
behavior.

.. note::
Expand All @@ -82,7 +81,8 @@ multi-threaded scaling. This means that these objects are never deallocated.
This is expected to be addressed in Python 3.14 with
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"addressed" how? That makes it sound like immortal objects are a problem. Are they?

`deferred reference counting <https://peps.python.org/pep-0703/#deferred-reference-counting>`_.

The objects that are immortalized are:
An object will be made immortal when a new thread is started for the first time after the main thread is running.
The following objects are immortalized:

* :ref:`function <user-defined-funcs>` objects declared at the module level
* :ref:`method <instance-methods>` descriptors
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