The Midway distributed shared memory system

Abstract

The authors describe the motivation, design, and performance of Midway, a programming system for a distributed shared memory multicomputer (DSM) such as an ATM-based cluster, a CM-5, or a Paragon. Midway supports a novel memory consistency model called entry consistency (EC). EC guarantees that shared data become consistent at a processor when the processor acquires a synchronization object known to guard the data. EC is weaker than other models described in the literature, such as processor consistency and release consistency, but it makes possible higher performance implementations of the underlying consistency protocols. Midway programs are written in C, and the association between synchronization objects and data must be made with explicit annotations. As a result, pure entry consistent programs can require more annotations than programs written to other models. Midway also supports the stronger release consistent and processor consistent models at the granularity of individual data items.