René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Multithreaded scaling regression in 3.13.1t","articleBody":"# Bug report\n\n### Bug description:\n\nhttps://github.com/python/cpython/pull/127114 changed the logic to immortalize certain objects when the first thread is created instead of the first *non-main* thread.\n\n\n3.13.0:\n```\nsgross@devfair0453:/raid/sgross/clean-cpython/Tools/ftscalingbench$ uv run -p 3.13.0t ftscalingbench.py\nRunning benchmarks with 20 threads\nobject_cfunction          14.3x faster\ncmodule_function          14.3x faster\nobject_lookup_special     14.3x faster\nmult_constant             13.8x faster\ngenerator                 13.8x faster\npymethod                  14.3x faster\npyfunction                14.0x faster\nmodule_function           14.2x faster\nload_string_const          2.5x slower\nload_tuple_const          13.5x faster\ncreate_pyobject           14.0x faster\ncreate_closure            14.0x faster\ncreate_dict               13.0x faster\nthread_local_read          3.0x slower\n```\n\n3.13.1:\n```\nsgross@devfair0453:/raid/sgross/clean-cpython/Tools/ftscalingbench$ uv run -p 3.13.1t ftscalingbench.py\nRunning benchmarks with 20 threads\nobject_cfunction           1.6x slower\ncmodule_function           1.9x slower\nobject_lookup_special      1.7x slower\nmult_constant             14.3x faster\ngenerator                  2.7x faster\npymethod                   2.3x slower\npyfunction                 3.1x slower\nmodule_function            2.1x slower\nload_string_const          2.1x slower\nload_tuple_const          13.1x faster\ncreate_pyobject            3.6x slower\ncreate_closure             4.3x slower\ncreate_dict               15.0x faster\nthread_local_read          3.0x slower\n```\n\n### CPython versions tested on:\n\n3.13\n\n### Operating systems tested on:\n\n_No response_\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-131989\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/colesbury","@type":"Person","name":"colesbury"},"datePublished":"2025-04-01T19:21:35.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/131988/cpython/issues/131988"}