A Study on Requests Serialization in Directory-Based Protocol for MESI Cache Coherence Protocol

Abstract

AbstractThe chip multiprocessor (CMP) uses cache coherence protocol to maintain the coherency between multiple copies of shared data. The cache coherence is the uniformity of shared data among multiple caches. So writes to a particular location in a cache should update other copies of the same data in other caches. However, coherency does not give information about the order of updation, and when updation of all caches shall be visible to serve the other requests. In addition to coherency, consistency is equally important to ensure that writes to different locations will be seen in order. An efficient cache coherence protocol maintains coherency between data and maintains consistency by faster retrieval of shared data. In this paper, we discuss how coherency and consistency are maintained in the MESI cache coherence protocol. MESI is popularly implemented in various commercial products. We discuss the functioning of directory protocol and MESI cache coherence protocol for CMP in which each processor has both private and shared caches.KeywordsChip multiprocessorMESI cache coherence protocolDirectory-based protocolShared caches