mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-08-03 00:23:06 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 6

bpo-35279: reduce default max_workers of ThreadPoolExecutor (GH-13618)

Browse source
This commit is contained in:
Inada Naoki 2019-05-28 21:02:52 +09:00 • committed by GitHub
parent 293e9f86b8
commit 9a7e5b1b42
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
4 changed files with 22 additions and 5 deletions
Download patch file Download diff file Expand all files Collapse all files

11
Lib/concurrent/futures/thread.py
View file

@ -129,9 +129,14 @@ class ThreadPoolExecutor(_base.Executor):
initargs: A tuple of arguments to pass to the initializer.
"""
if max_workers is None:
# Use this number because ThreadPoolExecutor is often
# used to overlap I/O instead of CPU work.
max_workers = (os.cpu_count() or 1) * 5
# ThreadPoolExecutor is often used to:
# * 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.
# 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)
if max_workers <= 0:
raise ValueError("max_workers must be greater than 0")

4
Lib/test/test_concurrent_futures.py
View file

@ -755,8 +755,8 @@ class ThreadPoolExecutorTest(ThreadPoolMixin, ExecutorTest, BaseTestCase):
def test_default_workers(self):
executor = self.executor_type()
self.assertEqual(executor._max_workers,
(os.cpu_count() or 1) * 5)
expected = min(32, (os.cpu_count() or 1) + 4)
self.assertEqual(executor._max_workers, expected)
def test_saturation(self):
executor = self.executor_type(4)