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gh-129752: Don't update adaptive counters when TLBC=0 in free-threading. - #155497

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corona10 merged 2 commits into
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corona10:gh-129752
Aug 13, 2026
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gh-129752: Don't update adaptive counters when TLBC=0 in free-threading.#155497
corona10 merged 2 commits into
python:mainfrom
corona10:gh-129752

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@corona10

@corona10 corona10 commented Aug 10, 2026 •
edited by bedevere-app Bot
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corona10 requested review from colesbury and mpage August 10, 2026 17:02
@corona10
corona10 requested a review from markshannon as a code owner August 10, 2026 17:02
@bedevere-app bedevere-app Bot mentioned this pull request Aug 10, 2026
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@corona10

corona10 commented Aug 10, 2026 •
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@mpage @colesbury

  • Adaptive counters are initialized to the unreachable state when thread-local bytecode is disabled, so this PR skips updating them. (I didn't want to make it complex for TLBC=0 case)
  • I expect that the performance impact should be within noise. (The default build is unchanged.)

@corona10 corona10 added needs backport to 3.13 bugs and security fixes needs backport to 3.14 bugs and security fixes needs backport to 3.15 pre-release feature fixes, bugs and security fixes labels Aug 10, 2026
mpage
mpage approved these changes Aug 12, 2026
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Performance results indeed look neutral.

A couple of nits inline but otherwise LGTM!

Comment thread Python/ceval_macros.h Outdated
Comment on lines +362 to +363
if (!backoff_counter_is_unreachable((COUNTER))) { \
(COUNTER) = advance_backoff_counter((COUNTER)); \

@mpage mpage Aug 12, 2026

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Nit: I think we end up evaluating COUNTER twice here. Probably not a huge deal, but we could avoid that by loading COUNTER into a temporary.

Comment thread Python/ceval_macros.h Outdated
Comment on lines +369 to +370
if (!backoff_counter_is_unreachable((COUNTER))) { \
(COUNTER) = pause_backoff_counter((COUNTER)); \

@mpage mpage Aug 12, 2026

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Same comment as above.

@corona10
corona10 enabled auto-merge (squash) August 12, 2026 23:45
@corona10
corona10 merged commit ee4fe00 into python:main Aug 13, 2026
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@miss-islington-app

miss-islington-app Bot commented Aug 13, 2026

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Thanks @corona10 for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14, 3.15.
🐍🍒⛏🤖

@miss-islington-app

miss-islington-app Bot commented Aug 13, 2026

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Sorry, @corona10, I could not cleanly backport this to 3.14 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker ee4fe00a8f72ea84a421bb626d7c78335c5c9ea1 3.14

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bedevere-app Bot commented Aug 13, 2026

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GH-155647 is a backport of this pull request to the 3.15 branch.

@bedevere-app bedevere-app Bot removed the needs backport to 3.15 pre-release feature fixes, bugs and security fixes label Aug 13, 2026
@miss-islington-app

miss-islington-app Bot commented Aug 13, 2026

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Sorry, @corona10, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker ee4fe00a8f72ea84a421bb626d7c78335c5c9ea1 3.13

@bedevere-app

bedevere-app Bot commented Aug 13, 2026

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GH-155715 is a backport of this pull request to the 3.14 branch.

@bedevere-app bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label Aug 13, 2026
corona10 added a commit to corona10/cpython that referenced this pull request Aug 13, 2026
@corona10
[3.14] pythongh-129752: Don't update adaptive counters when TLBC=0 in…
befac58 
… free-threading. (pythongh-155497)

(cherry picked from commit ee4fe00)

Co-authored-by: Donghee Na <donghee.na@python.org>
corona10 added a commit that referenced this pull request Aug 13, 2026
@corona10
[3.14] gh-129752: Don't update adaptive counters when TLBC=0 in free-…
c749534 
…threading. (gh-155497) (gh-155715)

(cherry picked from commit ee4fe00)
mbeijen pushed a commit to mbeijen/cpython that referenced this pull request Aug 14, 2026
@corona10 @mbeijen
pythongh-129752: Don't update adaptive counters when TLBC=0 in free-t…
b6bbc58 
…hreading. (pythongh-155497)
@BHUVANSH855

BHUVANSH855 commented Aug 18, 2026

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@corona10,
If the backport to 3.13 still needed, if yes, I can go with and propose a backport PR, if not we can remove the needs backport to 3.13 label to avoid confusions.

@corona10

corona10 commented Aug 18, 2026

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We don't need it

@corona10 corona10 removed the needs backport to 3.13 bugs and security fixes label Aug 18, 2026
@corona10
corona10 deleted the gh-129752 branch August 18, 2026 11:51
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@mpage mpage mpage approved these changes
@colesbury colesbury Awaiting requested review from colesbury
@markshannon markshannon Awaiting requested review from markshannon markshannon is a code owner

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