Speed up `test_weakref` in the free-threaded build

[colesbury]

The test_weakref test is one of the slowest tests when running in the free-threaded build.

The problem is the default period for the collect_in_thread() function is too short (100 µs). This isn't too much of a problem for the default build because the GIL switch interval is 5 ms, which effectively makes the smaller period irrelevant.

With the free-threaded build, this the 100 µs period means that the test spends the majority of its time calling gc.collect() nearly non-stop.

We should increase the period to 5 ms or so. On my machine, this decreases up the overall test_weakref time from 1 minute to 8 seconds.

cpython/Lib/test/test_weakref.py

Lines 84 to 103 in d909519

	@contextlib.contextmanager
	def collect_in_thread(period=0.0001):
	"""
	Ensure GC collections happen in a different thread, at a high frequency.
	"""
	please_stop = False
	def collect():
	while not please_stop:
	time.sleep(period)
	gc.collect()
	with support.disable_gc():
	t = threading.Thread(target=collect)
	t.start()
	try:
	yield
	finally:
	please_stop = True
	t.join()

Linked PRs

• gh-120065: Increase collect_in_thread period to 5 ms. #120068
• [3.13] gh-120065: Increase collect_in_thread period to 5 ms. (GH-120068) #120110