On the Distribution of Directory Information in a Software Controlled Distributed Shared Memory System
Distributed Shared Memory is a good solution to the scalability, complexity and high cost problems of large scale Shared Memory Multiprocessors, as well as to the difficulty of the programming model problem of the message passing Distributed Memory Multiprocessors. During recent years many software Distributed Shared Memory systems, operating on top of the Message Passing system have appeared. These systems are forced to use coherence protocols based on directory schemes for the preservation of the consistency of shared data. In this paper, we compare these schemes, focusing on fully centralized and fully distributed directory schemes. We construct a formal mathematical model of a 2-D grid Message Passing multiprocessor and predict the protocols' behaviour. 1 Introduction A Distributed Shared Memory (DSM) System is a multiprocessor system that, although its memory is physically distributed, offers the Shared Variable programming model to the user. The necessity of such systems has be...