A concurrency-optimal binary search tree

Abstract

The paper presents the first concurrency-optimal implementation of a binary search tree (BST). The implementation, based on a standard sequential implementation of a partially-external tree, ensures that every schedule, i.e., interleaving of steps of the sequential code, is accepted unless linearizability is violated. To ensure this property, we use a novel read-write locking protocol that protects tree edges in addition to its nodes. Our implementation performs comparably to the state-of-the-art BSTs and even outperforms them on few workloads, which suggests that optimizing the set of accepted schedules of the sequential code can be an adequate design principle for efficient concurrent data structures.