High-throughput coherence control and hardware messaging in Everest

Abstract

Everest is an architecture for high-performance cache coherence and message passing in partitionable distributed shared-memory systems that use commodity shared multiprocessors (SMPs) as building blocks. The Everest architecture is intended for use in designing future IBM servers using either PowerPC® or Intel® processors. Everest provides high-throughput protocol handling in three dimensions: multiple protocol engines, split request-response handling, and pipelined design. It employs an efficient directory subsystem design that matches the directory-access throughput requirement of high-performance protocol engines. A new directory design called the complete and concise remote (CCR) directory, which contains roughly the same amount of memory as a sparse directory but retains the benefits of a full-map directory, is used. Everest also supports system partitioning and provides a tightly integrated facility for secure, high-performance communication between partitions. Simulation results for both technical and commercial applications exploring some of the Everest design space are presented. The results show that the features of the Everest architecture can have significant impact on the performance of distributed shared-memory servers.