[3.12] gh-125997: suggest efficient alternatives for time.sleep(0) (GH-128752)

Doc/library/os.rst

@@ -5058,6 +5058,8 @@ information, consult your Unix manpages.
 The following scheduling policies are exposed if they are supported by the
 operating system.
 
+.. _os-scheduling-policy:
+
 .. data:: SCHED_OTHER
 
    The default scheduling policy.
@@ -5149,7 +5151,7 @@ operating system.
 
 .. function:: sched_yield()
 
-   Voluntarily relinquish the CPU.
+   Voluntarily relinquish the CPU. See :manpage:`sched_yield(2)` for details.
 
 
 .. function:: sched_setaffinity(pid, mask, /)

Doc/library/time.rst

@@ -367,6 +367,8 @@ Functions
    The suspension time may be longer than requested by an arbitrary amount,
    because of the scheduling of other activity in the system.
 
+   .. rubric:: Windows implementation
+
    On Windows, if *secs* is zero, the thread relinquishes the remainder of its
    time slice to any other thread that is ready to run. If there are no other
    threads ready to run, the function returns immediately, and the thread
@@ -375,12 +377,19 @@ Functions
    <https://learn.microsoft.com/windows-hardware/drivers/kernel/high-resolution-timers>`_
    which provides resolution of 100 nanoseconds. If *secs* is zero, ``Sleep(0)`` is used.
 
-   Unix implementation:
+   .. rubric:: Unix implementation
 
    * Use ``clock_nanosleep()`` if available (resolution: 1 nanosecond);
    * Or use ``nanosleep()`` if available (resolution: 1 nanosecond);
    * Or use ``select()`` (resolution: 1 microsecond).
 
+   .. note::
+
+      To emulate a "no-op", use :keyword:`pass` instead of ``time.sleep(0)``.
+
+      To voluntarily relinquish the CPU, specify a real-time :ref:`scheduling
+      policy <os-scheduling-policy>` and use :func:`os.sched_yield` instead.
+
    .. versionchanged:: 3.5
       The function now sleeps at least *secs* even if the sleep is interrupted
       by a signal, except if the signal handler raises an exception (see