Operating system virtualization

Abstract

Operating system (OS) virtualization can provide a number of important benefits, including transparent migration of applications, server consolidation, online OS maintenance, and enhanced system security. However, the construction of such a system presents a myriad of challenges, even for the most cautious developer, that if overlooked may result in a weak, incomplete virtualization. We present a detailed discussion of key implementation issues in providing OS virtualization in a commodity OS, including system call interposition, virtualization state management, and race conditions. We discuss our experiences in implementing such functionality across two major versions of Linux entirely in a loadable kernel module without any kernel modification. We present experimental results on both uniprocessor and multiprocessor systems that demonstrate the ability of our approach to provide fine-grain virtualization with very low overhead.