Optimizing Xen Hypervisor by Using Lock-Aware Scheduling

System virtualization enables multiple isolated running environments to be safely consolidated on a physical server, achieving better physical resource utilization and power saving. Virtual machine has been an essential component in most of the cloud/data-center system software stacks. However, virtualization brings negative impacts on synchronization in guest operating system (guest OS) and thus dramatically degrades the performance of the virtual machine. Therefore, how to effectively eliminate or alleviate the disadvantageous impacts has been becoming an open research issue. Xen hyper visor is a wide used virtualized platform in the area of industry and research. In this work, our aim is to optimize Xen hyper visor to minimize the impacts of virtualization on synchronization in guest OS. We propose a lock-aware scheduling mechanism, which focuses on improving the performance of virtual machines where spin-lock primitive is frequently invoked, as well as guaranteeing the scheduling fairness. The mechanism adopts a flexible scheduling algorithm based on the information of spin-lock, which is updated dynamically. We have modified Xen and Linux to implement the scheduling mechanism. Experimental results show that the optimized system can nearly eliminate the impacts of virtualization on synchronization and improve the performance of virtual machines substantially. Although the proposed mechanism is aimed at optimizing Xen hyper visor, it can also be applied to some other Para virtualized platforms.