fix(json): route the traversal-feedback counters through the hot thread-local cache

[proggeramlug]

Summary

scripts/check_thread_locals.py (the "Enforce the thread-local policy ratchet" step of tls-budget.yml's self-test-checkers job, which runs on every PR) fails on current main for two files. One of them is mine: #10150 declared json/traversal_feedback.rs's two per-thread counters with a raw thread_local!, and the policy allows none (every declaration goes through crate::perry_thread_local!, which lands the address in the thread's hot cache instead of paying _tlv_get_addr, #7469). This converts both; the syntax and every .with() call site are unchanged.

The second failing file, regex/perex_owner.rs (one raw declaration, from #10166), is not touched here, so the job stays red on this PR for that file alone.

Validation

• python3 scripts/check_thread_locals.py --self-test passes; python3 scripts/check_thread_locals.py no longer lists json/traversal_feedback.rs (only regex/perex_owner.rs remains).
• python3 scripts/gc_runtime_root_holders.py: OK (the two counters keep their existing not_a_gc_pointer verdicts).
• cargo check --release -p perry-runtime: clean.
• RUST_TEST_THREADS=1 cargo test --release -p perry-runtime traversal_feedback: 3 passed, 0 failed.

Summary by CodeRabbit

• Performance
  • Improved JSON parsing performance by optimizing per-thread counter access.
• Documentation
  • Added a changelog entry describing the JSON parsing performance improvement.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: 594a0075-a763-4941-a2d8-0de5eac42047

📥 Commits

Reviewing files that changed from the base of the PR and between 5d3bf85 and 388e83a.

📒 Files selected for processing (2)

• changelog.d/10203-traversal-feedback-hot-tls.md
• crates/perry-runtime/src/json/traversal_feedback.rs

Included review availability: Your plan provides up to 8 included reviews per hour; 7 remain after this review.

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📝 Walkthrough

Walkthrough

The JSON traversal feedback counters now use crate::perry_thread_local!. The comment describes their per-parse reads. A changelog fragment documents the change and its thread-local policy effect.

Changes

Traversal feedback TLS

Layer / File(s)	Summary
Hot TLS counter update crates/perry-runtime/src/json/traversal_feedback.rs, changelog.d/10203-traversal-feedback-hot-tls.md	SCORE and EAGER_RUN now use crate::perry_thread_local!. The comment and changelog describe the hot thread-local access and policy update.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 388e8

This is a localized performance-policy change with validation passing and no identified merge-blocking behavior.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: routing JSON traversal-feedback counters through the hot thread-local cache.
Description check	✅ Passed	The description is on-topic and mostly complete. It explains the change, motivation, affected files, unrelated remaining failure, and validation results. It does not use the template headings for Chan…
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 1…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch json/traversal-feedback-hot-tls

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[proggeramlug]

CI on this head compared against main's run 34757970864 (fresh, same period): cargo-test fails the same single unrelated test (native_stack::tests::stack_top_respects_custom_thread_stack_sizes, 3711 passed); the gap suite's failing set is identical to main's 10 (empty difference both ways); the failed jobs are main's (warnings, lint public-baseline freshness, check API docs drift, gap-suite shards, gc-stress matrix/merge).

The tls-budget.yml self-test-checkers job still fails on this PR for crates/perry-runtime/src/regex/perex_owner.rs alone (from #10166, not touched here); json/traversal_feedback.rs is no longer listed. Taking this out of draft.

[proggeramlug]

Landed via merge train #10216 (rebase-merged; main 5d3bf86823, tree identical to the train), cherry-picked onto 44e78debf9 with the version bump to 0.5.1559. Validation and CI attribution are in #10216.