Power-efficient and High-performance Block I/O Framework for Mobile Virtualization Systems

This paper proposes an efficient block I/O framework for mobile virtualization environments containing a few CPU cores. We improve the block I/O layer of a virtual machine (VM) so that it can provide higher I/O performance and lower CPU usage. Generally, virtualized systems suffer from I/O performance degradation due to inherent virtualization overheads. Recently suggested polling-based I/O virtualization techniques can achieve high performance improvement. However, it has a drawback in CPU utilization, so it is difficult for embedded or mobile systems to adopt the polling mechanism because they do not have sufficient CPU cores. The proposed block I/O framework in this paper monitors the status of I/O requests and CPU utilization in order to dynamically switch the I/O process mode between exit mode and polling mode, and change the polling interval depending on the amount of current I/O requests. It can achieve both higher I/O performance and lower CPU utilization. The experimental results show that our proposed framework outperformed existing exit-based mechanism by achieving 18.8% better throughput and 15.1% lower CPU usage. Moreover, in comparison with the system using only polling mechanism, it can reduce the CPU usage by 10% with almost no throughput degradation.