On the Correctness of Program Execution When Cache Coherence Is Maintained Locally at Data-Sharing Boundaries in Distributed Shared Memory Multiprocessors

Abstract

Emerging multiprocessor architectures such as chip multiprocessors, embedded architectures, and massively parallel architectures, demand faster, more efficient, and more scalable cache coherence schemes. In devising more cost-efficient schemes, formal insights into a system model is deemed useful. We, in this paper, build formalisms for execution in cache based Distributed shared-memory multiprocessors (DSM) obeying Release Consistency model, and derive conditions for cache coherence. A cost-efficient cache coherence scheme without directories is designed. Our approach relies on processor directed coherence actions, which are early in nature. The scheme exploits sharing information provided by a programmer-centric framework. Per-processor coherence buffers (CB) are employed to impose coherence on live shared variables between consecutive release points in the execution. Simulation of 8 entry 4-way associative CB based system achieves a speedup of 1.07-4.31 over full-map 3-hop directory scheme for six of the SPLASH-2 benchmarks.