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perf(once-cell): avoid locking on uncontended initialization - #412
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orthur2 merged 2 commits intoNov 8, 2026
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Kaileshwar16
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November 7, 2026 12:40
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Thanks for your contribution! LGTM.
This was referenced Nov 8, 2026
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Reduce fresh OnceCell initialization cost by acquiring two of three internal semaphore permits. The spare permit allows uncontended release to avoid locking the wait queue while preserving exclusive initialization and existing cancellation handling.
On Linux, ten alternating benchmark samples reduced median fresh initialization time from 352 ms to 236 ms for six million operations (33%). Already-initialized reads and four-waiter performance remained within measurement noise.
Add regression coverage for publication, cancellation, retry, and waiter progress, plus an already-initialized read benchmark.
Fixes #398.