Hardware Support for Spin Management in Overcommitted Virtual Machines

Overview

Multiprocessor Operating Systems (OSs) pose several unique and conflicting challenges to System Virtual Machines (System VMs). For example, most existing system VMs resort to gang scheduling a guest OS's virtual processors (VCPUs) to avoid OS synchronization overhead. However, gang scheduling is infeasible for some application domains, and is inflexible in other domains. In an overcommitted environment, an individual guest OS has more VCPUs than available physical processors (PCPUs), precluding the use of gang scheduling. In such an environment, the authors demonstrate a more than two-fold in-crease in runtime when transparently virtualizing a chip-multiprocessor's cores.