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Abstract : |
Directory-based protocols have been proposed as an efficient means of implementing cache coherence in large-scale shared-memory multiprocessors. This thesis explores the trade-offs in the design of cache coherence directories by examining the organization of the directory information, the options in the design of the coherency protocol, and the implementation of the directory and protocol. The traditional directory organization that maintains a full valid bit vector per directory entry is unsuitable for large-scale machines due to high storage overhead. This thesis proposes several alternate organizations. Limited pointers directories replace the bit vector with several pointers that indicate those caches containing the data. Although this scheme performs well across a wide range of workloads, its performance does not improve as the read/write ratio becomes very large. To address this drawback, a dynamic pointer allocarion directory is proposed. This directory allocates pointers from a pool to particular memory blocks as they are needed. Since the pointers may be allocated to any block on the memory module, the probability of running short of pointers is very small. Among the set of possible organizations, dynamic pointer, |
