gh-116604: Fix test_gc on free-threaded build

[colesbury]

The free-threaded GC only does full collections, so it uses a threshold that is a maximum of a fixed value (default 2000) and proportional to the number of live objects. If there were many live objects after the previous collection, then the threshold may be larger than 10,000 causing test_indirect_calls_with_gc_disabled to fail.

This manually sets the threshold to (1000, 0, 0) for the test. The 0 disables the proportional scaling.

• Issue: C API: PyGC_Disable() not respected #116604

[colesbury]

!buildbot nogil

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @colesbury for commit 3bc0f08 🤖

The command will test the builders whose names match following regular expression: nogil

The builders matched are:

• AMD64 Ubuntu NoGIL PR
• AMD64 Windows Server 2022 NoGIL PR
• ARM64 MacOS M1 Refleaks NoGIL PR
• x86-64 MacOS Intel NoGIL PR
• AMD64 Ubuntu NoGIL Refleaks PR
• ARM64 MacOS M1 NoGIL PR
• x86-64 MacOS Intel ASAN NoGIL PR

[corona10]

So, in short, setting the fixed threshold for the default build test and free-threading test, right?

[colesbury]

@corona10, also for threshold of (1000, 0, 0), threshold[1] == 0 disables the proportional scaling and only uses the fixed threshold of 1000.

cpython/Python/gc_free_threading.c

Lines 979 to 982 in 8e2aab7

	// objects. A few tests rely on immediate scheduling of the GC so we ignore
	// the scaled threshold if generations[1].threshold is set to zero.
	return (count > gcstate->long_lived_total / 4 ||
	gcstate->generations[1].threshold == 0);