Service without servers [operating system architecture]

We propose a new style of operating system architecture appropriate for microkernel-based operating systems: services are implemented as a combination of shared libraries and dedicated server processes. Shared libraries implement performance critical portions of each system service, while dedicated servers implement the parts of each service that do not require high performance or that are difficult to implement in an application. Dedicated servers might be used, for example, to manage shared state that must persist across process lifetimes or to implement high-level abstractions that are difficult or impossible to provide in a library. Our initial experiments show that this approach to operating system structure can yield performance that is comparable to monolithic kernel systems while retaining all the modularity advantages that led industry to adopt microkernel technology in the first place. Since services reside in libraries, an application is free to use the library that is most appropriate. This approach can even yield better performance than monolithic kernel systems by allowing the shared libraries to be closely coupled with the applications, thereby exploiting application-specific knowledge in policy decisions