Towards Better Performance Per Watt in Virtual Environments on Asymmetric Single-ISA Multi-core Systems

Single-ISA heterogeneous multicore architectures promise to deliver plenty of cores with varying complexity, speed and performance in the near future. Virtualization enables multiple operating systems to run concurrently as distinct, independent guest domains, thereby reducing core idle time and maximizing throughput. This paper seeks to identify a heuristic that can aid in intelligently scheduling these virtualized workloads to maximize performance while reducing power consumption. We propose that the controlling domain in a Virtual MachineMonitor or hypervisor is relatively insensitive to changes in core frequency, and thus scheduling it on a slower core saves power while only slightly affecting guest domain performance. We test and validate our hypothesis and further propose a metric, the Combined Usage of a domain, to assist in future energy-efficient scheduling. Our preliminary findings show that the Combined Usage metric can be used as a starting point to gauge the sensitivity of a guest domain to variations in the controlling domain's frequency.