A case for NUMA-aware contention management on multicore systems

Abstract

On multicore systems, contention for shared resources occurs when memory-intensive threads are co-scheduled on cores that share parts of the memory hierarchy, such as last-level caches and memory controllers. Previous work investigated how contention could be addressed via scheduling. A contention-aware scheduler separates competing threads onto separate memory hierarchy domains to eliminate resource sharing and, as a consequence, to mitigate contention. However, all previous work on contention-aware scheduling assumed that the underlying system is UMA (uniform memory access latencies, single memory controller). Modern multicore systems, however, are NUMA, which means that they feature non-uniform memory access latencies and multiple memory controllers. We discovered that state-of-the-art contention management algorithms fail to be effective on NUMA systems and may even hurt performance relative to a default OS scheduler. In this paper we investigate the causes for this behavior and design the first contention-aware algorithm for NUMA systems. 1