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Title: GH-139951: Fix major GC performance regression by markshannon · Pull Request #140262 · python/cpython · GitHub

Open Graph Title: GH-139951: Fix major GC performance regression by markshannon · Pull Request #140262 · python/cpython

X Title: GH-139951: Fix major GC performance regression by markshannon · Pull Request #140262 · python/cpython

Description: This PR: Counts number of actually tracked objects, instead of trackable objects. This ensures that untracking tuples has the desired effect of reducing GC overhead Does not track most untrackable tuples during creation. This prevents large numbers of small tuples causing excessive GCs. For the example in the original report this makes performance on main a bit better than 3.13. Benchmarking results show this is about neutral on performance otherwise. Issue: gh-139951

Open Graph Description: This PR: Counts number of actually tracked objects, instead of trackable objects. This ensures that untracking tuples has the desired effect of reducing GC overhead Does not track most untrackable...

X Description: This PR: Counts number of actually tracked objects, instead of trackable objects. This ensures that untracking tuples has the desired effect of reducing GC overhead Does not track most untrackable...

Opengraph URL: https://github.com/python/cpython/pull/140262

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2e8d020 Fix major GC performance regression markshannon Oct 16, 2025 https://github.com/python/cpython/pull/140262/commits/2e8d02023cd84bc103b0a8130fd3c9d376748ad1
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c5836be Address review comments markshannon Oct 20, 2025 https://github.com/python/cpython/pull/140262/commits/c5836be5e2ee35626b7849b227a09438672e2a37
bde53f4 Up limit to 100000 markshannon Oct 20, 2025 https://github.com/python/cpython/pull/140262/commits/bde53f4e80d6abcac2925e66031b75c88e1f834a
1c2030a Remove erroneous comment markshannon Oct 20, 2025 https://github.com/python/cpython/pull/140262/commits/1c2030a93ef4928c5d3a4044d7e4aa8af112ad7a
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