spin v0.1.5 — TTAS slow path with adaptive backoff

[hayabusa-cloud]

Introduction

Package spin provides minimal spin primitives for performance-critical code paths: Lock (non-fair spinlock), Wait (adaptive spin-wait), Pause (architecture-specific CPU hint), and Yield (cooperative sleep). Designed for ultra-short critical sections where OS mutex overhead is prohibitive, with zero allocations on hot paths.

Lock acquisition uses FAA (Fetch-And-Add) for O(n) coherence traffic under contention, compared to O(n²) with CAS-based spinlocks. Architecture-specific pause instructions are provided for amd64, arm64, riscv64, loong64, ppc64le, s390x, and 386.

Usage

var lk spin.Lock
lk.Lock()
// critical section (< 1µs)
lk.Unlock()

Highlights

Lock slow path rewritten to TTAS (test-and-test-and-set) with local-counter adaptive backoff, reducing cache-line invalidations under contention and guaranteeing forward progress on low-core-count machines.

What's Changed

Improvements

• Rewrite Lock slow path to TTAS: spin on read-only Load, attempt FAA only when lock appears free (TTAS slow path with adaptive backoff #8)

Documentation

• Document FAA/TTAS design rationale in Lock type and method comments (TTAS slow path with adaptive backoff #8)
• Document intentional FAA-on-failure behavior in Try (TTAS slow path with adaptive backoff #8)

Chore

• Bump Go to 1.26 (TTAS slow path with adaptive backoff #8)

Compatibility

• Go: 1.26+
• Platforms: linux/amd64, linux/arm64, linux/riscv64, linux/loong64, linux/ppc64le, linux/s390x, linux/386, wasm

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This discussion was created from the release spin v0.1.5 — TTAS slow path with adaptive backoff.