Perf&Fair: A Progress-Aware Scheduler to Enhance Performance and Fairness in SMT Multicores

Nowadays, high performance multicore processors implement multithreading capabilities. The processes running concurrently on these processors are continuously competing for the shared resources, not only among cores, but also within the core. While resource sharing increases the resource utilization, the interference among processes accessing the shared resources can strongly affect the performance of individual processes and its predictability. In this scenario, process scheduling plays a key role to deal with performance and fairness. In this work we present a process scheduler for SMT multicores that simultaneously addresses both performance and fairness. This is a major design issue since scheduling for only one of the two targets tends to damage the other. To address performance, the scheduler tackles bandwidth contention at the L1 cache and main memory. To deal with fairness, the scheduler estimates the progress experienced by the processes, and gives priority to the processes with lower accumulated progress. Experimental results on an Intel Xeon E5645 featuring six dual-threaded SMT cores show that the proposed scheduler improves both performance and fairness over two state-of-the-art schedulers and the Linux OS scheduler. Compared to Linux, unfairness is reduced to a half while still improving performance by 5.6 percent.