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Unit test test_incremental_gc_handles_fast_cycle_creation sometimes fails #133532
Description
Bug report
Bug description:
On a debug build on Linux AMD64, this fails for me:
./python -m test -uall test___all__ test_atexit test_audit test_ast test_argparse test_gc
[...]
test test_gc failed -- Traceback (most recent call last):
File "/home/nas/src/cpython/Lib/contextlib.py", line 85, in inner
return func(*args, **kwds)
File "/home/nas/src/cpython/Lib/test/test_gc.py", line 1184, in test_incremental_gc_handles_fast_cycle_creation
self.assertLess(new_objects, 27_000, f"Heap growing. Reached limit after {i} iterations")
~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 27013 not less than 27000 : Heap growing. Reached limit after 6579 iterationsThe exact set of tests required before test_gc seems to depend on other factors. More reliable command might be:
./python -m test -uall test___all__ test_buffer test_atexit test_audit test_bigaddrspace test_bdb test_abc test_bufio test_ast test_base64 test_annotationlib test_baseexception test__colorize test__interpreters test_asyncgen test_augassign test_bigmem test_binascii test_bz2 test_abstract_numbers test__osx_support test_c_locale_coercion test_bool test_argparse test_gc
CPython versions tested on:
CPython main branch
Operating systems tested on:
Linux
Activity
pythongh-133532: Run GC fast cycles test in subprocess.
nascheme commentedon May 6, 2025
There seems to be some non-linear behavior happening. Creating a few thousand extra container objects (I used empty lists) before running the test results in the following.
A log curve seems to fit the data pretty closely.
markshannon commentedon May 7, 2025
The larger the heap, the longer it takes to scan it, so there's more lag in collecting cycles. That's my guess.
Merge branch 'main' into pythongh-133532-gc-test-in-subprocess
Merge branch 'main' into pythongh-133532-gc-test-in-subprocess
Merge branch 'main' into pythongh-133532-gc-test-in-subprocess
gh-133532: Run GC fast cycles test in subprocess. (gh-133533)
pythongh-133532: Run GC fast cycles test in subprocess. (pythongh-133533
[3.14] gh-133532: Run GC fast cycles test in subprocess. (gh-133533) (g…
pythongh-133532: Run GC fast cycles test in subprocess. (pythongh-133533
nascheme commentedon Jul 14, 2025
The GH-133533 change has resolved this issue.
pythongh-133532: Run GC fast cycles test in subprocess. (pythongh-133533