Performance comparisons of buffer coherency policies

A comparison is made of four buffer coherency policies: check on access, check on access with periodic notification, selective notification, and broadcast invalidation. These policies differ in their basic approaches on how and when the invalidated granules are identified, and hence, achieve different tradeoffs between buffer hits and overhead of notifications. Analytic models are developed to evaluate the buffer hit probability, CPU overhead, and overall response time under these coherency policies. The analysis is validated through simulations. It is found that the difference in buffer hit probabilities is very sensitive to the skewness of the data access and is further affected by the number of nodes, update rates, and the buffer size