Group Ratio Round-Robin: O(1) Proportional Share Scheduling for Uniprocessor and Multiprocessor Systems

We present Group Ratio Round-Robin (GR), the first proportional share scheduler that combines accurate proportional fairness scheduling behavior with O(1) scheduling overhead on both uniprocessor and multiprocessor systems. GR uses a simple grouping strategy to organize clients into groups of similar processor allocations which can be more easily scheduled. Using this strategy, GR combines the benefits of low overhead round-robin execution with a novel ratio-based scheduling algorithm. GR introduces a novel frontlog mechanism and weight readjustment algorithm to operate effectively on multiprocessors. GR provides fairness within a constant factor of the ideal generalized processor sharing model for client weights with a fixed upper bound and preserves its fairness properties on multiprocessor systems. We have implemented GR in Linux and measured its performance. Our experimental results show that GR provides much lower scheduling overhead and much better scheduling accuracy than other schedulers commonly used in research and practice.