Fine-grained, dynamic user customization of operating systems

Application performance can be improved by customizing the operating system kernel at run time. Inserting application code directly into the kernel avoids the costly protection-domain switches required in traditional interprocess communications. Our design for a customizable operating system structures the kernel as a set of object-oriented frameworks. The user can then perform fine-grained customization by subclassing kernel classes and inserting objects into the kernel. User code is written in a safe, object-oriented language (Sun's Java), which is interpreted or dynamically compiled in the kernel. Objects in the kernel, regardless of their origin, interact with each other seamlessly through ordinary object invocation. This extension technique has the advantage that a user can build directly on top of kernel frameworks using object invocation just as if the user were a system implementor without compromising system safety.