A Practical Look at Micro-Kernels and Virtual Machine Monitors

In this paper, we look at two different approaches used to provide embedded system support for virtualization and virtual machine monitors for consumer electronics and mobile devices. We compare the micro-kernel approach, which has been a popular choice for building embedded operating systems with the Virtual Machine Monitor (VMM) or hypervisor approach widely deployed in general purpose computing environments such as desktops and data center servers. Comparison criteria are based on virtualization use cases that are typical of Consumer Electronics (CE) systems such as mobile devices and IPTV. These approaches are further evaluated based on performance and on their ability to allow re-use of existing (often real-time) software as well as modern open operating systems such as Linux while remaining as transparently as possible. Such transparency can come through different paths, including: leveraging of hardware virtualization support, minimal modifications to the original operating system internals (kernel, device drivers, etc.), and the ability to use existing operating system applications as-is and without the need to port them to a new environment. An analysis of the fundamental principles behind each approach is presented with a discussion of their impact on existing operating environments, together with practical performance results based on existing micro-kernels and real-time hypervisor benchmarks. We conclude that mapping the VMM (hypervisor) approach used in data centers to the needs of embedded systems is a better option for the support of complete operating systems (as guests) than extending micro-kernels for such functionality.