Towards a practical snapshot algorithm

Abstract

An atomic snapshot memory is an implementation of a multiple location shared memory that can be atomically read in its entirety without having to prevent concurrent writing. The design of wait-free implementations of atomic snapshot memories has been the subject of extensive theoretical research in recent years. This paper introduces the coordinated-collect algorithm, a novel wait-free atomic snapshot construction which we believe is a first step in taking snapshots from theory to practice. Unlike former algorithms, it uses currently available multiprocessor synchronization operations to provide an algorithm that has only O(1) update complexity and O(n) scan complexity, with very small constants. Empirical evidence collected on a simulated distributed shared-memory multiprocessor shows that coordinated-collect outperforms all known wait-free, lock-free, and locking algorithms in terms of overall throughput and latency.