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gh-125997: ensure that time.sleep(0) is not delayed on non-Windows platforms #128274

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gh-125997: ensure that time.sleep(0) is not delayed on non-Windows platforms #128274

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3754e9e
Ensure that `time.sleep(0)` does not accumulate delays.
picnixz Dec 26, 2024
3c0c4e6
update globals
picnixz Dec 26, 2024
c18f15f
blurb
picnixz Dec 26, 2024
8d270f2
fix Windows compilation
picnixz Dec 26, 2024
2996937
use a fresh `timeval` variable for select(2) portability
picnixz Dec 27, 2024
80de853
ensure that `errno=0` when calling `pysleep[zero_posix]`
picnixz Dec 27, 2024
c7aa428
removing `assert(errno == 0)`
picnixz Dec 27, 2024
f15436e
add errors assertions
picnixz Dec 27, 2024
68e2988
simplify code
picnixz Dec 29, 2024
afc6186
add comments for `time.sleep(0)`
picnixz Dec 30, 2024
f6a817f
improve time.sleep() tests
picnixz Dec 30, 2024
fb9eb41
update `os` scheduling policy docs
picnixz Dec 30, 2024
ecb9636
update docs
picnixz Dec 30, 2024
1ed9877
add What's New
picnixz Dec 30, 2024
23b4740
fix typo
picnixz Jan 2, 2025
40155ff
optimize `time.sleep(0)` path
picnixz Jan 3, 2025
153b326
update docs
picnixz Jan 3, 2025
7e351c9
update tests
picnixz Jan 3, 2025
285c54a
revert un-necessary docs updates
picnixz Jan 3, 2025
434da31
remove performance tests
picnixz Jan 6, 2025
ff06516
implement platform compile-time dependent `time.sleep(0)`
picnixz Jan 6, 2025
40d56f1
address Victor's review
picnixz Jan 7, 2025
c4ce9cc
update blurb
picnixz Jan 7, 2025
54b6dde
simplify `pysleep`
picnixz Jan 7, 2025
405e473
add newline for readability
picnixz Jan 7, 2025
b803045
revert to a `select()` alternative
picnixz Jan 7, 2025
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update docs
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@picnixz
picnixz committed Jan 3, 2025
commit 153b326ffd7aea805275b8f93f5909f103a74196
12 changes: 0 additions & 12 deletions Doc/library/time.rst
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Expand Up @@ -397,18 +397,10 @@ Functions

.. rubric:: Unix implementation

If *secs* is zero, ``select()`` is used. Otherwise:

* Use ``clock_nanosleep()`` if available (resolution: 1 nanosecond);
* Or use ``nanosleep()`` if available (resolution: 1 nanosecond);
* Or use ``select()`` (resolution: 1 microsecond).

.. note::

To voluntarily relinquish the CPU, specify a read-time :ref:`scheduling
policy <os-scheduling-policy>` (see :manpage:`sched_yield(2)`) and use
:func:`os.sched_yield` instead.

.. audit-event:: time.sleep secs

.. versionchanged:: 3.5
Expand All @@ -423,10 +415,6 @@ Functions
.. versionchanged:: 3.13
Raises an auditing event.

.. versionchanged:: next
On Unix, ``time.sleep(0)`` always uses ``select()``, even if the
``clock_nanosleep()`` or ``nanosleep()`` functions are available.

.. index::
single: % (percent); datetime format

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5 changes: 2 additions & 3 deletions Doc/whatsnew/3.14.rst
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Expand Up @@ -621,9 +621,8 @@ Two new events are added: :monitoring-event:`BRANCH_LEFT` and
time
----

* Ensure that :func:`time.sleep(0) <time.sleep>` does not accumulate delays on
POSIX platforms. The implementation always uses :manpage:`select(2)` even if
the :manpage:`clock_nanosleep` or :manpage:`nanosleep` functions are present.
* Ensure that :func:`time.sleep(0) <time.sleep>` does not degrade over time
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@vstinner vstinner Jan 6, 2025

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I suppose that you're referring to performance:

Suggested change
* Ensure that :func:`time.sleep(0) <time.sleep>` does not degrade over time
* Ensure that :func:`time.sleep(0) <time.sleep>` performance does not degrade over time

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@picnixz picnixz Jan 6, 2025

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Depending on the resolution of this PR (namely, whether we eventually use select()), I'll amend the NEWS so I won't commit that suggestion for now.

on non-Windows platforms.
(Contributed by Bénédikt Tran in :gh:`125997`.)


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4 changes: 2 additions & 2 deletions Misc/NEWS.d/next/Library/2024-12-26-13-09-25.gh-issue-125997.Vsibep.rst
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@@ -1,2 +1,2 @@
Ensure that :func:`time.sleep(0) <time.sleep>` does not accumulate delays on
non-Windows platforms. Patch by Bénédikt Tran.
Ensure that :func:`time.sleep(0) <time.sleep>` does not degrade over time
on non-Windows platforms. Patch by Bénédikt Tran.