ACFS: A Completely Fair Scheduler for Asymmetric Single-ISA Multicore Systems

Single-ISA (instruction set architecture) asymmetric multicore processors (AMPs) were shown to deliver higher performance per watt and area than symmetric CMPs (Chip Multi-Processors) for applications with diverse architectural requirements. A large body of work has demonstrated that this potential of AMP systems can be realizable via OS scheduling. Yet, existing schedulers that seek to deliver fairness on AMPs do not ensure that equal-priority applications experience the same slowdown when sharing the system. Moreover, most of these schemes are also subject to high throughput degradation and fail to effectively deal with user priorities. In this work we propose ACFS, an asymmetry-aware completely fair scheduler that seeks to optimize fairness while ensuring acceptable throughput. Our evaluation on real AMP hardware, and using scheduler implementations on a general-purpose OS, demonstrates that ACFS achieves an average 11% fairness improvement over state-of-the-art schemes, while providing better system throughput.