Module ring 

Fixed-capacity latency statistics — REQ-CLK-006.

LatencyRing is a sliding window of u64 nanos: record is O(1) and evicts the oldest sample when capacity is exceeded; stats is exact over the current window with zero heap allocation — it sorts a stack-resident copy (CAP × 8 B scratch; default 4096 → 32 KiB, chosen for ≥ 64 KiB stacks) and reports min/max/mean/p50/p99/p99.9.

Percentiles use the nearest-rank algorithm, re-implemented lean from the percentile-kit pattern: percentile-kit is L2, and an L1 crate must not depend upward (estate layers.md rule 1) — so the algorithm is copied, not linked. No recursion anywhere (guaranteed for constrained stacks): the sort is an iterative heapsort.

Structs

IntervalStats

Exact interval statistics over the current window (nanosecond resolution). All zeros for an empty ring. REQ-CLK-006.

LatencyRing

Fixed-capacity (const-generic) ring of u64 nanos — a sliding window, not an accumulator. Allocation-free on every path: stats() works from a stack-resident scratch copy sized by CAP (default 4096 → 32 KiB — document your stack when embedding with larger capacities). REQ-CLK-006.