Shared Memory Consistency Models

The shared memory systems should support parallelization at the computation (multiprocessor), communication (Network-on-Chip, NoC) and memory architecture levels to exploit the potential performance benefits. Such systems are facing the critical issues of memory consistency and coherence. Memory consistency issue arises due to the unconstrained operations which sometimes lead to the unexpected behavior of the systems. Memory consistency models are used to resolve this issue. Relaxed or weaker consistency models enforce less ordering constraints on the memory operations and exploit system optimizations compared to the stricter models. This book discusses the novel realization schemes and scalability analysis of strict Sequential Consistency (SC) model and relaxed memory consistency models: Total Store Ordering (TSO), Partial Store Ordering (PSO), Weak Ordering (WO), Release Consistency (RC), and Protected Release Consistency (PRC) in the NoC based distributed shared memory multiprocessor systems. This study should help the average readers and professionals to understand the critical issue of memory consistency both in the NoC based systems and general purpose multiprocessor systems.