bench: keep third-party and frozen baselines out of CodSpeed

[connortsui20]

Summary

Second of three stacked PRs on CodSpeed flakiness. The first resizes benchmarks, the third unifies the allocator.

The three noisiest series in the whole suite are benchmarks of code Vortex does not own or does not change:

Benchmark	Flips on unrelated PRs (all PRs)	Max swing
lane_kernels.rs: arrow_checked_add_u32 (neon leg)	64 (97)	67%
lane_kernels.rs: arrow_checked_add_u32 (avx2 leg)	48 (65)	22%
collect_bool.rs: words_gather_scalar[65536] (avx2 leg)	45 (62)	15%
lane_kernels.rs: arrow_checked_add_u32 (avx512 leg)	30 (41)	22%

arrow_checked_add_u32 runs the arrow-rs checked add over the same data as lanezip_checked_add_u32. words_gather_scalar runs a frozen copy of the previous scalar collect_bool loop. Neither can regress because of a pull request, so a change in their number is never actionable, and on the walltime legs they flipped on about half of all pull requests.

Changes

Both benchmarks stay in the tree for local cargo bench comparisons, but leave CodSpeed: they lose #[cpu_features], which takes them off the walltime legs, and gain #[cfg(not(codspeed))], which keeps them out of the simulation build. Imports and fixture fields that only they use are gated the same way. The guide gets a short section on keeping third-party and frozen baselines out of CodSpeed.

The other arrow baselines (arrow_narrow_* and arrow_widen_* in lane_kernels.rs) run in simulation, have not flipped, and are left as they are.

Checks run:

• cargo clippy --locked --benches -p vortex-buffer -p vortex-compute -- -D warnings
• RUSTFLAGS="--cfg codspeed -D warnings" cargo check --locked --benches -p vortex-buffer -p vortex-compute, to confirm the gated build has no unused items
• cargo +nightly-2026-09-10 fmt on the touched crates

🤖 Generated with Claude Code

https://claude.ai/code/session_01B6ApyxEXpjiasZbQptsypn

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Generated by Claude Code

[codspeed]

Merging this PR will degrade performance by 81.04%

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 10 improved benchmarks
❌ 131 regressed benchmarks
✅ 2043 untouched benchmarks
🆕 24 new benchmarks
⏩ 287 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	from_vec_drop_arrow[256]	2.8 µs	133.9 µs	-97.9%
❌	Simulation	from_vec_drop_arrow[1024]	2.9 µs	136.1 µs	-97.89%
❌	Simulation	from_vec_drop_vortex[256]	3.1 µs	142.3 µs	-97.84%
❌	Simulation	from_vec_drop_vortex[1024]	3.1 µs	144.8 µs	-97.84%
❌	Simulation	from_vec_drop_bytes[1024]	2.2 µs	99.4 µs	-97.8%
❌	Simulation	from_vec_drop_bytes[256]	2.2 µs	96.5 µs	-97.74%
❌	Simulation	from_vec_drop_vortex[64]	3 µs	114.7 µs	-97.37%
❌	Simulation	from_vec_drop_arrow[64]	2.8 µs	105.3 µs	-97.33%
❌	Simulation	allocate_freeze_drop_vortex_minimal_alignment[64]	3.3 µs	109.1 µs	-96.95%
❌	Simulation	allocate_freeze_drop_vortex_custom[64]	4.2 µs	135.6 µs	-96.91%
❌	Simulation	allocate_freeze_drop_vortex[64]	3.4 µs	109.3 µs	-96.86%
❌	Simulation	from_vec_drop_bytes[64]	2.2 µs	68.6 µs	-96.82%
❌	Simulation	allocate_freeze_drop_vortex[256]	3.5 µs	109.4 µs	-96.81%
❌	Simulation	allocate_freeze_drop_bytes[64]	3.2 µs	97 µs	-96.74%
❌	Simulation	allocate_freeze_drop_bytes[256]	3.2 µs	97.1 µs	-96.68%
❌	Simulation	allocate_freeze_drop_bytes[1024]	3.3 µs	97.1 µs	-96.63%
❌	Simulation	allocate_freeze_drop_arrow[64]	3.8 µs	104.9 µs	-96.38%
❌	Simulation	allocate_freeze_drop_vortex_minimal_alignment[65536]	6 µs	148.5 µs	-95.99%
❌	Simulation	allocate_freeze_drop_vortex_minimal_alignment[16384]	6 µs	148.3 µs	-95.99%
❌	Simulation	allocate_freeze_drop_vortex[1024]	6 µs	148.6 µs	-95.96%
...	...	...	...	...	...

ℹ️ Only the first 20 benchmarks are displayed. Go to the app to view all benchmarks.

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing ct/codspeed-local-only-baselines (0b9bec1) with develop (b0ea625)²}

Footnotes

1. 287 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on develop (5c7f370) during the generation of this report, so b0ea625 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩