subms-spsc-ring-buffer (Rust)

Wait-free single-producer single-consumer ring buffer.

Sizing

Power-of-two capacity (rounded up from the request). Index modulo via bitmask, not %. Per-side counter padding to 128 bytes to avoid false sharing across the head/tail line.

Implementation notes

• Producer caches the consumer head; consumer caches the producer tail. Re-read through the atomic only when the cache says full / empty.
• Memory ordering: Release on publish (tail/head store), Acquire on the opposite-side load, Relaxed on own-side reads.
• Producer/Consumer split enforces SPSC at the type level - moving the wrong handle to the wrong thread is a compile error.

Quality bar

• Reference impl: Java JCTools SpscArrayQueue, Agrona OneToOneConcurrentArrayQueue (Aeron). Rust rtrb.
• Sub-ms claim under: enqueue/dequeue p99 < 1 ms across 100k ops with capacity 1024, on a 2-core sibling pair.
• Not claimed: MPMC; multi-core throughput claims on logical (HT) sibling pairs.

Bench numbers

Filled in once the bench is run on the canonical hardware. The cookbook page carries the measured values - never invented.

Consumed by

Timer wheel (subms-timer-wheel) uses an SPSC ring as the schedule-from-any-thread inbox; the timer thread is the consumer.