gh-109649: Use os.process_cpu_count() (#110165)

Replace os.cpu_count() with os.process_cpu_count() in modules:

* compileall
* concurrent.futures
* multiprocessing

Replace os.cpu_count() with os.process_cpu_count() in programs:

* _decimal deccheck.py test
* freeze.py
* multissltests.py
* python -m test (regrtest)
* wasm_build.py

Other changes:

* test.pythoninfo logs os.process_cpu_count().
* regrtest gets os.process_cpu_count() / os.cpu_count() in headers.
This commit is contained in:
Victor Stinner 2023-10-01 03:14:57 +02:00 committed by GitHub
parent 53eb9a676f
commit a46e960768
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16 changed files with 50 additions and 16 deletions

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@ -90,7 +90,7 @@ compile Python sources.
.. cmdoption:: -j N
Use *N* workers to compile the files within the given directory.
If ``0`` is used, then the result of :func:`os.cpu_count()`
If ``0`` is used, then the result of :func:`os.process_cpu_count()`
will be used.
.. cmdoption:: --invalidation-mode [timestamp|checked-hash|unchecked-hash]

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@ -188,6 +188,10 @@ And::
ThreadPoolExecutor now reuses idle worker threads before starting
*max_workers* worker threads too.
.. versionchanged:: 3.13
Default value of *max_workers* is changed to
``min(32, (os.process_cpu_count() or 1) + 4)``.
.. _threadpoolexecutor-example:
@ -243,7 +247,7 @@ to a :class:`ProcessPoolExecutor` will result in deadlock.
An :class:`Executor` subclass that executes calls asynchronously using a pool
of at most *max_workers* processes. If *max_workers* is ``None`` or not
given, it will default to the number of processors on the machine.
given, it will default to :func:`os.process_cpu_count`.
If *max_workers* is less than or equal to ``0``, then a :exc:`ValueError`
will be raised.
On Windows, *max_workers* must be less than or equal to ``61``. If it is not
@ -301,6 +305,10 @@ to a :class:`ProcessPoolExecutor` will result in deadlock.
different start method. See the :func:`os.fork` documentation for
further explanation.
.. versionchanged:: 3.13
*max_workers* uses :func:`os.process_cpu_count` by default, instead of
:func:`os.cpu_count`.
.. _processpoolexecutor-example:
ProcessPoolExecutor Example

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@ -996,13 +996,13 @@ Miscellaneous
This number is not equivalent to the number of CPUs the current process can
use. The number of usable CPUs can be obtained with
``len(os.sched_getaffinity(0))``
:func:`os.process_cpu_count`.
When the number of CPUs cannot be determined a :exc:`NotImplementedError`
is raised.
.. seealso::
:func:`os.cpu_count`
:func:`os.cpu_count` and :func:`os.process_cpu_count`
.. function:: current_process()
@ -2214,7 +2214,7 @@ with the :class:`Pool` class.
callbacks and has a parallel map implementation.
*processes* is the number of worker processes to use. If *processes* is
``None`` then the number returned by :func:`os.cpu_count` is used.
``None`` then the number returned by :func:`os.process_cpu_count` is used.
If *initializer* is not ``None`` then each worker process will call
``initializer(*initargs)`` when it starts.
@ -2249,6 +2249,10 @@ with the :class:`Pool` class.
.. versionadded:: 3.4
*context*
.. versionchanged:: 3.13
*processes* uses :func:`os.process_cpu_count` by default, instead of
:func:`os.cpu_count`.
.. note::
Worker processes within a :class:`Pool` typically live for the complete
@ -2775,7 +2779,7 @@ worker threads rather than worker processes.
:meth:`~multiprocessing.pool.Pool.terminate` manually.
*processes* is the number of worker threads to use. If *processes* is
``None`` then the number returned by :func:`os.cpu_count` is used.
``None`` then the number returned by :func:`os.process_cpu_count` is used.
If *initializer* is not ``None`` then each worker process will call
``initializer(*initargs)`` when it starts.

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@ -91,6 +91,13 @@ Other Language Changes
of the ``optimize`` argument.
(Contributed by Irit Katriel in :gh:`108113`).
* :mod:`multiprocessing`, :mod:`concurrent.futures`, :mod:`compileall`:
Replace :func:`os.cpu_count` with :func:`os.process_cpu_count` to select the
default number of worker threads and processes. Get the CPU affinity
if supported.
(Contributed by Victor Stinner in :gh:`109649`.)
New Modules
===========

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@ -666,7 +666,7 @@ class ProcessPoolExecutor(_base.Executor):
_check_system_limits()
if max_workers is None:
self._max_workers = os.cpu_count() or 1
self._max_workers = os.process_cpu_count() or 1
if sys.platform == 'win32':
self._max_workers = min(_MAX_WINDOWS_WORKERS,
self._max_workers)

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@ -139,10 +139,10 @@ class ThreadPoolExecutor(_base.Executor):
# * CPU bound task which releases GIL
# * I/O bound task (which releases GIL, of course)
#
# We use cpu_count + 4 for both types of tasks.
# We use process_cpu_count + 4 for both types of tasks.
# But we limit it to 32 to avoid consuming surprisingly large resource
# on many core machine.
max_workers = min(32, (os.cpu_count() or 1) + 4)
max_workers = min(32, (os.process_cpu_count() or 1) + 4)
if max_workers <= 0:
raise ValueError("max_workers must be greater than 0")

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@ -200,7 +200,7 @@ class Pool(object):
self._initargs = initargs
if processes is None:
processes = os.cpu_count() or 1
processes = os.process_cpu_count() or 1
if processes < 1:
raise ValueError("Number of processes must be at least 1")
if maxtasksperchild is not None:

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@ -426,7 +426,7 @@ class Regrtest:
if self.num_workers < 0:
# Use all CPUs + 2 extra worker processes for tests
# that like to sleep
self.num_workers = (os.cpu_count() or 1) + 2
self.num_workers = (os.process_cpu_count() or 1) + 2
# For a partial run, we do not need to clutter the output.
if (self.want_header

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@ -546,6 +546,9 @@ def display_header(use_resources: tuple[str, ...],
cpu_count = os.cpu_count()
if cpu_count:
process_cpu_count = os.process_cpu_count()
if process_cpu_count and process_cpu_count != cpu_count:
cpu_count = f"{process_cpu_count} (process) / {cpu_count} (system)"
print("== CPU count:", cpu_count)
print("== encodings: locale=%s, FS=%s"
% (locale.getencoding(), sys.getfilesystemencoding()))

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@ -239,6 +239,7 @@ def collect_os(info_add):
'getresgid',
'getresuid',
'getuid',
'process_cpu_count',
'uname',
):
call_func(info_add, 'os.%s' % func, os, func)

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@ -25,7 +25,7 @@ class ThreadPoolExecutorTest(ThreadPoolMixin, ExecutorTest, BaseTestCase):
def test_default_workers(self):
executor = self.executor_type()
expected = min(32, (os.cpu_count() or 1) + 4)
expected = min(32, (os.process_cpu_count() or 1) + 4)
self.assertEqual(executor._max_workers, expected)
def test_saturation(self):

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@ -0,0 +1,4 @@
:mod:`multiprocessing`, :mod:`concurrent.futures`, :mod:`compileall`:
Replace :func:`os.cpu_count` with :func:`os.process_cpu_count` to select the
default number of worker threads and processes. Get the CPU affinity if
supported. Patch by Victor Stinner.

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@ -1301,7 +1301,7 @@ if __name__ == '__main__':
out, _ = p.communicate()
write_output(out, p.returncode)
N = os.cpu_count()
N = os.process_cpu_count()
t = N * [None]
for i in range(N):

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@ -130,7 +130,7 @@ def prepare(script=None, outdir=None):
if not MAKE:
raise UnsupportedError('make')
cores = os.cpu_count()
cores = os.process_cpu_count()
if cores and cores >= 3:
# this test is most often run as part of the whole suite with a lot
# of other tests running in parallel, from 1-2 vCPU systems up to

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@ -151,7 +151,10 @@ class AbstractBuilder(object):
build_template = None
depend_target = None
install_target = 'install'
jobs = os.cpu_count()
if hasattr(os, 'process_cpu_count'):
jobs = os.process_cpu_count()
else:
jobs = os.cpu_count()
module_files = (
os.path.join(PYTHONROOT, "Modules/_ssl.c"),

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@ -516,7 +516,11 @@ class BuildProfile:
def getenv(self) -> Dict[str, Any]:
"""Generate environ dict for platform"""
env = os.environ.copy()
env.setdefault("MAKEFLAGS", f"-j{os.cpu_count()}")
if hasattr(os, 'process_cpu_count'):
cpu_count = os.process_cpu_count()
else:
cpu_count = os.cpu_count()
env.setdefault("MAKEFLAGS", f"-j{cpu_count}")
platenv = self.host.platform.getenv(self)
for key, value in platenv.items():
if value is None: