Description

sergey-miryanov

opened on Apr 18, 2026

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Feature or enhancement

Proposal:

It was decided to revert the incremental GC and restore the generational GC from Python 3.13.

After discussing with @nascheme, we plan to forward-port the generational GC from 3.13 with minimal changes.

Here is the plan:

3.14

1. Forward-port the generational GC from 3.13 with minimal changes
2. Backport the heap_size calculation logic

3.15

1. Forward port from 3.14
2. Backport weakref's callbacks changes (b6b99bf, 350c58b, 654b8d9)
3. Backport changes required for pystats (c98c5b3)
4. Backport GC frame for Tachyon (336366f)
5. Backport extended data for callbacks: duration, candidates (598d4c6, 227b9d3)
6. Backport gc-stats from external processes (Add a module for monitoring GC statistics #146527)

AFAICT, these are all the changes that need to be forward-ported or backported for the 3.14 and 3.15.

Has this already been discussed elsewhere?

I have already discussed this feature proposal on Discourse

Links to previous discussion of this feature:

https://discuss.python.org/t/reverting-the-incremental-gc-in-python-3-14-and-3-15/107014

Linked PRs

• [3.14] GH-148726: Forward-port generational GC #148720
• GH-148726: Forward-port generational GC. #148746
• [3.14] GH-148726: Forward-port generational GC (another way) #148772
• [3.14] GH-148726: Add heap_size to _gc_runtime_state #149025
• GH-148726: Add heap_size to generational GC #149195
• gh-148726: Document the GC change in What's New in Python 3.14 #149209
• [3.14] gh-148726: Document the GC change in What's New in Python 3.14 (GH-149209) #149249
• gh-148726: Add gc changes to What's New #149398

Reacted by Neil Schemenauer and Shamil

Activity

1. sergey-miryanov

   added

   type-featureA feature request or enhancementA feature request or enhancement

   on Apr 18, 2026
2. StanFromIreland

   added

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   3.14bugs and security fixesbugs and security fixes

   3.15bugs and security fixesbugs and security fixes

   on Apr 18, 2026
3. sergey-miryanov

   self-assigned this

   on Apr 18, 2026
4. hugovk

   added a commit that references this issue on Apr 26, 2026

   [3.14] GH-148726: Forward-port generational GC (#148720)

   9a7e205
5. sergey-miryanov commented on Apr 26, 2026

   

   sergey-miryanov

   on Apr 26, 2026

   ContributorAuthor

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   With #148720 landed, I'll open a PR for the heap_size backport.
6. hugovk

   added a commit that references this issue on Apr 29, 2026

   [3.14] GH-148726: Add heap_size to _gc_runtime_state (#149025)

   4d0ae4c
7. sergey-miryanov commented on Apr 29, 2026

   

   sergey-miryanov

   on Apr 29, 2026

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   #149025 has merged. I plan to forward-port the changes to the 3.15 branch once #148746 is merged.
8. nascheme

   added a commit that references this issue on Apr 30, 2026

   GH-148726: Forward-port generational GC. (GH-148746)

   1575a81
9. hugovk

   added 2 commits that reference this issue on May 1, 2026

   gh-148726: Document the GC change in What's New in Python 3.14 (#149209)

   4e3811f

   [3.14] gh-148726: Document the GC change in What's New in Python 3.14 (…

   7c3cc0f
10. pablogsal

    added a commit that references this issue on May 4, 2026

    GH-148726: Add heap_size to generational GC (#149195)

    e89568f
11. sergey-miryanov commented on May 5, 2026

    

    sergey-miryanov

    on May 5, 2026

    ContributorAuthor

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    All planned tasks done. Closing this out.

    Reacted by Hugo van Kemenade
12. sergey-miryanov

    closed this as completedon May 5, 2026
13. hugovk commented on May 5, 2026

    

    hugovk

    on May 5, 2026

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    Thank you for all your work on this!

    Reacted by Sergey Miryanov
14. hauntsaninja commented on May 5, 2026

    

    hauntsaninja

    on May 5, 2026

    Contributor

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    Might be worth documenting in 3.15 What's New as well?
15. hugovk commented on May 5, 2026

    

    hugovk

    on May 5, 2026

    Member

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    Yes, I created #149398.

    Reacted by Sergey Miryanov
16. hugovk

    added a commit that references this issue on May 5, 2026

    gh-148726: Add gc changes to What's New (#149398)

    586c97a
17. tmeijn

    added a commit that references this issue on May 8, 2026

    build(deps): update uv to v0.11.11

    d2f8c7c
18. hbjydev

    added a commit that references this issue on May 29, 2026

    feat(github-release): update release uv ( 0.10.9 → 0.11.17 ) (#34)

    a462067
19. hbjydev

    added a commit that references this issue on Jun 10, 2026

    feat(github-release): update release uv ( 0.10.9 → 0.11.19 ) (#43)

    13c3e1b

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