PaS: A Preemption-aware Scheduling Interface for Improving Interactive Performance in Consolidated Virtual Machine Environment

As virtualization technology is used widely in cloud computing, there are more and more interactive workloads being deployed on virtual machine (VM) environment. Although improving interactive performance has been heavily studied in operating system area, in consolidated VM environment, the improvements of guest OS are usually offset by the more coarse-grained VM scheduler, which may cause poor interactive performance. The guest OS scheduler and VM scheduler are totally independent with each other, which leads to the so called ´semantic gap´. To reduce this semantic gap, this paper presents PaS (Preemption-aware Scheduling) as an extension of VM scheduling interface. PaS introduces only two interfaces: one to register VM preemption conditions, the other to check if a VM is preempting. Thanks to the sophisticated techniques of interactive-process identification and optimization in traditional OS, it is trivial for guest OS to use the new interfaces: only 10 lines of code are added into Linux 2.6.18.8. The evaluation results show that PaS can significantly improve the interactive performance of consolidated VMs while keeping the fairness and performance isolation.