On the Scalability ofDemand - Driven Parallel

Demand-driven systems follow the model where customers enter the system, request some service, and then depart. Examples are databases, transaction processing systems and operating systems, which form the system software layer between the applications and the hardware. Achieving scalability at the system software layer is critical for the scalability of the system as a whole, and yet this layer has largely been ignored. In this paper, we characterize the scalability of the system software layer of demand-driven parallel systems based on fundamental metrics of quantitative system performance analysis. We develop a set of suucient conditions so that if a system satisses these conditions, then the system is scalable. We further argue that in practice these conditions are also necessary. In the remainder of the paper, we use the necessary and suucient conditions to develop a set of practical design guidelines, to study the eeect of application workloads, and to examine the scalability behavior of a system with only a limited number of processors.