Hapax Locks : Value-Based Mutual Exclusion

TL;DR

Hapax Locks is a new mutual exclusion algorithm that offers constant-time operations, FIFO order, space efficiency, and low coherence traffic, matching state-of-the-art performance while being easier to integrate.

Contribution

The paper introduces Hapax Locks, a simple, efficient, and environment-agnostic locking algorithm with constant-time paths and FIFO order, improving ease of integration.

Findings

Comparable performance to top locks in latency and scalability

Fewer runtime constraints and dependencies

Minimal coherence traffic under contention

Abstract

We present Hapax Locks, a novel locking algorithm that is simple, enjoys constant-time arrival and unlock paths, provides FIFO admission order, and which is also space efficient and generates relatively little coherence traffic under contention in the common case. Hapax Locks offer performance (both latency and scalability) that is comparable with the best state of the art locks, while at the same time Hapax Locks impose fewer constraints and dependencies on the ambient runtime environment, making them particularly easy to integrate or retrofit into existing systems or under existing application programming interfaces Of particular note, no pointers shift or escape ownership between threads in our algorithm.