Processor pool-based scheduling for large-scale NUMA multiprocessors

Abstract

Large-scale Non-Uniform Memory Access (NUMA) multiprocessors are gaining increased attention due to their potential for achieving high performance through the replication of relatively simple components. Because of the complexity of such systems, scheduling algorithms for parallel applications are crucial in realizing the performance potential of these systems. In particular, scheduling methods must consider the scale of the system, with the increased likelihood of creating bottlenecks, along with the NUMA characteristics of the system, and the benefits to be gained by placing threads close to their cocle and data. We propose a class of scheduling algorithms based on processor pools. A processor pool is a software construct fOr Organizing and managing a large number of processors by di riding them into groups called pools. The parallel threads of a job are run in a single processor pool, unless there are performance advantages for a job to span multiple pools. Several jobs may share one pool. Our simulation experiments show that proces. sor pool-based scheduling may effectively reduce the average job response time. The performance improvements attained by using processor pools increase with the average parallelism of the jobs, the load level of the system, the differentials in memory access costs, and the likelihood of having system bottlenecks. As the system size increases, while maintaining the wo~kload composition and intensity, we observed that processor pools can be used to provide significant performance improvements. We therefore conclude that processor pool-based scheduling may be an effective and efficient technique for scalable systems.