Exploiting unbalanced thread scheduling for energy and performance on a CMP of SMT processors

This paper explores thread scheduling on an increasingly popular architecture: chip multiprocessors with simultaneous multithreading cores. Conventional multiprocessor scheduling, applied to this architecture, will attempt to balance the thread load across cores. This research demonstrates that such an approach eliminates one of the big advantages of this architecture - the ability to use unbalanced schedules to allocate the right amount of execution resources to each thread. However, accommodating unbalanced schedules creates several difficulties, the biggest being the fact that the search space of all schedules (both balanced and unbalanced) is much greater than that of the balanced schedules alone. This work proposes and evaluates scheduling policies that allow the system to identify and migrate toward good thread schedules, whether the best schedules are balanced or unbalanced.