bench: reuse multiline terminator Finder

[mjc]

Summary

Reuses one process-global memchr::memmem::Finder for the fixed multiline terminator. The framer still owns all boundary handling; candidate collection, suffix checks, and split-read behavior are unchanged.

E2E benchmark evidence

Measurements used an AMD Ryzen 9 5950X (32 logical CPUs), main commit 145b36c6b86621dccfe965926b0ef501ffd33b06, and Finder source revision e176fef31432ed36dc101471dfa1c94cc1650908.

Each run is the stock cache-miss E2E script after a whole-target clean, with RUSTFLAGS=-C target-cpu=native. It builds the measured proxy and pinned nntpbench itself, then exercises all 112 default cells: 10 GiB per cell, 728,320-byte article responses, article-only mix, pipeline depth 32, and the 1/2/4/8 thread × 1/2/4/8/16/32/64 backend-connection × 1/4/8/16 client matrix.

Fresh main averaged 3,546.6 MiB/s. Two clean Finder repetitions averaged 3,564.3 MiB/s (+0.5%) and 3,560.8 MiB/s (+0.4%). Their paired medians were -0.4% and +0.4%; geometric means were +0.6% and -0.5%; win/loss counts were 50/62 and 63/49. Proxy CPU changed -0.8% and +0.2%.

The repeats are effectively flat with broad per-cell variance, so they do not demonstrate a reliable end-to-end speedup. The CSVs are retained locally rather than committed.

The commit hook ran cargo fmt and cargo clippy successfully; the branch-added benchmark note documents the workload and both repetitions.

Summary by CodeRabbit

• Performance

  • Improved processing efficiency for multiline message terminators by reusing a cached search pattern.

• Documentation

  • Added benchmark results comparing the updated implementation with the previous version on a cache-miss end-to-end run.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI (base), Organization UI (inherited)

Review profile: ASSERTIVE

Plan: Advanced

Run ID: 1e7d94c5-c4d1-41e7-984f-e092e0a57675

📥 Commits

Reviewing files that changed from the base of the PR and between e176fef and 33a1e60.

📒 Files selected for processing (1)

• docs/development.md

Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

The module now lazily caches a memchr::memmem::Finder for the NNTP terminator. terminator_ends reuses the finder. Development documentation now records benchmark measurements and their limitations.

Changes

Terminator Search Optimization

Layer / File(s)	Summary
Cache and reuse the terminator finder src/session/multiline_framing.rs	The module adds a lazily initialized terminator finder and uses it in terminator_ends instead of creating an inline search iterator.
Record benchmark results docs/development.md	The Benchmarks section now includes measured control and Finder candidate results, comparison statistics, CPU changes, and notes that the results do not demonstrate a reliable end-to-end speedup.

Priority: ⬇️ Low

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

Change: Refactor

Merge Risk: ⚪ Minimal · up to 33a1e

The cached Finder is compatible with the repository toolchain and preserves the tested framing semantics; the documented benchmark results are appropriately qualified.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 1 files. (1 skipped: 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.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: reusing the multiline terminator Finder. It matches the implementation and benchmark objective.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch bench/multiline-terminator-finder

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