Chapter 15 - Memory System Design Analysis

Abstract

The importance of memory system performance as a limiter of computer system performance is widely recognized. This chapter examines performance issues and proceeds along a generalized framework to discuss memory system performance characteristics. The goal of this chapter is to provide illustrative examples that a potential system architect can follow and gain potential insight into how his or her memory system should or could be analyzed. Workload characteristics analyze the various single threaded workloads in terms of their respective request inter-arrival rate, locality characteristics, and read-versus-write traffic ratio. The rationale for the examination of the workload characteristics is to provide a basis for understanding different types of workload characteristics. More modern memory systems designed for multi-threaded and multi-core processors must be designed to handle complex multi-threaded and multiple concurrent process workloads. Systems designed for highly threaded, on-line transaction processing (OLTP) types of applications will have drastically different memory system requirements than systems designed for bandwidth-intensive scientific workloads. The Request Access Distance (RAD) analytical framework provides a set of mathematical equations to analyze sustainable bandwidth characteristics, given specific memory-access patterns and scheduling policies from the memory controller. The RAD analytical framework is then used to examine a variety of issues relating to system-level parallelism and bandwidth characteristics.