Brief Announcement: Relay: A Cache-Coherence Protocol for Distributed Transactional Memory

Abstract

Distributed transactional memory promises to alleviate difficulties with lock-based (distributed) synchronization and object performance bottlenecks in distributed systems. The design of the cache- coherence protocol is critical to the performance of distributed transactional memory systems. We evaluate the performance of a cache-coherence protocol by measuring its worst-case competitive ratio — i.e., the ratio of its makespan to the makespan of the optimal cache-coherence protocol. We establish the upper bound of the competitive ratio and show that it is determined by the worst-case number of abortions, maximum locating stretch, and maximum moving stretch of the protocol — the first such result. We present the Relay protocol, a novel cache-coherence protocol, which optimizes these values, and evaluate its performance. We show that Relay’s competitive ratio is significantly improved by a factor of O(N _i ) for N _i transactions requesting the same object when compared against past distributed queuing protocols.