diff options
Diffstat (limited to 'Lib/concurrent/futures/process.py')
| -rw-r--r-- | Lib/concurrent/futures/process.py | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py index d7e2478..dd14eae 100644 --- a/Lib/concurrent/futures/process.py +++ b/Lib/concurrent/futures/process.py @@ -57,6 +57,7 @@ import threading import weakref from functools import partial import itertools +import sys import traceback # Workers are created as daemon threads and processes. This is done to allow the @@ -109,6 +110,12 @@ def _python_exit(): EXTRA_QUEUED_CALLS = 1 +# On Windows, WaitForMultipleObjects is used to wait for processes to finish. +# It can wait on, at most, 63 objects. There is an overhead of two objects: +# - the result queue reader +# - the thread wakeup reader +_MAX_WINDOWS_WORKERS = 63 - 2 + # Hack to embed stringification of remote traceback in local traceback class _RemoteTraceback(Exception): @@ -505,9 +512,16 @@ class ProcessPoolExecutor(_base.Executor): if max_workers is None: self._max_workers = os.cpu_count() or 1 + if sys.platform == 'win32': + self._max_workers = min(_MAX_WINDOWS_WORKERS, + self._max_workers) else: if max_workers <= 0: raise ValueError("max_workers must be greater than 0") + elif (sys.platform == 'win32' and + max_workers > _MAX_WINDOWS_WORKERS): + raise ValueError( + f"max_workers must be <= {_MAX_WINDOWS_WORKERS}") self._max_workers = max_workers |