Topology-aware equipartitioning with coscheduling on multicore systems

Over the last decade, multicore architectures have become omnipresent. Today, they are used in the whole product range from server systems to handheld computers. The deployed software still undergoes the slow transition from sequential to parallel. This transition, however, is gaining more and more momentum due to the increased availability of more sophisticated parallel programming environments, which replace the some-times crude results of ad-hoc parallelization. Combined with the ever increasing complexity of multicore architectures, this results in a scheduling problem that is different from what it has been, because features such as non-uniform memory access, shared caches, or simultaneous multithreading have to be considered. In this paper, we compare different ways of scheduling multiple parallel applications. Due to emerging parallel programming environments, we only consider malleable applications, i. e., applications where the parallelism degree can be changed on the fly. We propose a topology-aware scheduling scheme that combines equipartitioning and coscheduling. It does not suffer from the drawbacks of the individual concepts and also allows to run applications at different degrees of parallelisms without compromising fairness. We find that topology-awareness increases performance for all evaluated workloads. The combination with coscheduling is more sensitive towards the executed workloads. However, the gained versatility allows new use cases to be explored, which were not possible before.