perf(allocator/bitset): store bits as usizes

[overlookmotel]

BitSet store bits as usizes, instead of u8s. This serves 2 purposes:

1. Data in arena is almost all pointer-aligned, so there's little point storing odd-numbered arrays of bytes, as they'll likely be padded to a multiple of 8 bytes anyway. Higher alignment makes the contents of a BitSet less likely to span multiple cache lines.

2. It makes creating a new BitSet faster. Vec::from_iter_in is unfortunately not very efficient, and does a bounds check on each turn of the loop. So writing bits / 64 items (usizes) is faster than writing bits / 8 items (u8s).

[overlookmotel]

• perf(allocator/bitset): store bits in Box<[usize]> #13455
• 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 👈 (View in Graphite)
• feat(allocator): introduce BitSet type #13449
• main

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[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #13450 will improve performances by 31.74%

_{Comparing 08-30-perf_allocator_bitset_store_bits_as_usize_s (cdfa48d) with main (edeebc6)¹}

Summary

⚡ 3 improvements
✅ 34 untouched benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	mangler[binder.ts]	895 µs	811.9 µs	+10.24%
⚡	mangler[cal.com.tsx]	4.1 ms	3.1 ms	+31.74%
⚡	mangler[react.development.js]	292.8 µs	279.4 µs	+4.78%

Footnotes

1. No successful run was found on main (afa0877) during the generation of this report, so edeebc6 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[graphite-app]

Merge activity

• Aug 31, 4:58 AM UTC: Boshen added this pull request to the Graphite merge queue.
• Aug 31, 5:05 AM UTC: Merged by the Graphite merge queue.