This paper describes a novel approach to providing modular and extensible operating system functionality and encapsulated environments based on a synthesis of microkernel and virtual machine concepts. We have developed a software-based virtualizable architecture called Fluke that allows recursive virtual machines (virtual machines running on other virtual machines) to be implemented efficiently by a microkernel running on generic hardware. A complete virtual machine interface is provided at each level; efficiency derives from needing to implement only new functionality at each level. This infrastructure allows common OS functionality, such as process management, demand paging, fault tolerance, and debugging support, to be provided by cleanly modularized, independent, stackable virtual machine monitors, implemented as user processes. It can also provide uncommon or unique OS features, including the above features specialized for particular applications ’ needs, virtual machines transparently distributed cross-node, or security monitors that allow arbitrary untrusted binaries to be executed safely. Our prototype implementation of this model indicates that it is practical to modularize operating systems this way. Some types of virtual machine layers impose almost no overhead at all, while others impose some overhead (typically 0–35%), but only on certain classes of applications.

The growth and popularity of loosely-coupled distributed systems such as the World Wide Web and the touting of Java-based systems as the solution to the issues of software maintenance, flexibility, and security are changing the research emphasis away from traditional single node operating system issues. Apparently, the view is that traditional OS issues are either solved problems or minor problems. By contrast, we believe that building such vast distributed systems upon the fragile infrastructure provided by today's operating systems is analogous to building castles on sand. In this paper we outline the supporting arguments for these views and describe an OS design that supports secure encapsulation of the foreign processes that will be increasingly prevalent in tomorrow's distributed systems. 1 1 Why Global Applications Require More from Local Systems 1.1 The Global Vision The Call for Papers for this conference envisions that an "as-yet-unbuilt system will allow hundreds of millio...

Providing efficient device driver support in the Fluke operating system presents novel challenges, which stem from two conflicting factors: (i) a design and maintenance requirement to reuse unmodified legacy device drivers, and (ii) the mismatch between the Fluke kernel's internal execution environment and the execution environment expected by these legacy device drivers. This thesis presents a solution to this conflict: a framework whose design is based on running device drivers as usermode servers, which resolves the fundamental execution environment mismatch. This approach

Distributed systems such as client-server applications and cluster-based parallel computation are an important part of modern computing. Distributed computing allows the balancing of processing load, increases program modularity, isolates functionality, and can provide an element of fault tolerance. In these environments, systems must be able to synchronize and share data through some mechanism for remote interprocess communication (IPC). Although distributed systems have many advantages, they also pose several challenges. One important challenge is transparency. It is desirable that applications can be written to a communication interface that hides the details of distribution. One way to achieve transparency is through the extension of local communication mechanisms over a network for remote communication. The ability to transparently extend local communication depends on the semantics of the local IPC mechanisms. Unfortunately, those semantics are often driven by other architectural...