perf(allocator/bitset): store bits in Box<[usize]>

[overlookmotel]

BitSet store data in a Box<[usize]> instead of Vec<usize>. This has 2 advantages:

1. Box<[usize]> is smaller - 16 bytes vs 24 for Vec<usize>.
2. Marginally faster to initialize.

Also, improve the implementation of BitSet::clone_in to avoid bounds checks. As usize is Copy, we can just use ptr::copy_nonoverlapping to copy the whole slice in one go, instead of cloning entries one by one.

[overlookmotel]

• perf(allocator/bitset): store bits in Box<[usize]> #13455 👈 (View in Graphite)
• feat(allocator): add Box::from_non_null method #13454
• perf(allocator/bitset): initialize BitSet with memset #13451
• perf(allocator/bitset): store bits as usizes #13450
• feat(allocator): introduce BitSet type #13449
• main

---

How to use the Graphite Merge Queue

Add either label to this PR to merge it via the merge queue:

• 0-merge - adds this PR to the back of the merge queue
• hotfix - for urgent hot fixes, skip the queue and merge this PR next

You must have a Graphite account in order to use the merge queue. Sign up using this link.

An organization admin has enabled the Graphite Merge Queue in this repository.

Please do not merge from GitHub as this will restart CI on PRs being processed by the merge queue.

This stack of pull requests is managed by Graphite. Learn more about stacking.

[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #13455 will not alter performance

_{Comparing 08-30-perf_allocator_store_bits_in_box_usize_ (b92fa4f) with main (e6cdaa6)¹}

Summary

✅ 37 untouched benchmarks

Footnotes

1. No successful run was found on main (b92fa4f) during the generation of this report, so e6cdaa6 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[Boshen]

Merge activity

• Aug 31, 4:58 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Aug 31, 5:10 AM UTC: Graphite rebased this pull request, because this pull request is set to merge when ready.
• Aug 31, 7:14 AM UTC: Boshen added this pull request to the Graphite merge queue.
• Aug 31, 7:20 AM UTC: Merged by the Graphite merge queue.

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.