Analysis of directory based cache coherence schemes with multistage networks
Ashwini K. Nanda, Hong Jiang · 1992
Designing efficient cache coherence schemes for shared memory multiprocessors has attracted much attention of the researchers in the area. Snoopy cache protocols have been designed for bus based multiprocessors. However, the snoopy protocols are not applicable to general interconnection networks. On the other hand, the directory based cache protocols adapt very well to any kind of interconnection network such as a Multistage Network. Since different protocols have different cost overheads, and may give different performance, the protocol to be used must be wisely selected. Although there has been some simulation studies on the behavior of different directory schemes proposed in the literature, there has been no systematic analytical model for these schemes. In this paper we develop a detailed analytical model of the various directory schemes on a Multistage Interconnection Network. The shared miss ratios are computed analytically, and the performance of the various schemes is compared. Results are presented to show that the directories do not form a system bottleneck contrary to popular belief.