Implementing Operating Systems without Kernels

Most contemporary operating systems are structured around a central monolithickernel (or micro-kernel). An alternative is to construct operating systemswithout a kernel. In this approach, operating system abstractions (processes,threads, virtual memory, communication) are implemented as application-levelcode, with the attendant flexibility and extensibility that many userapplications require.We are building such a kernel-less operating system, using optimizedcross-domain calls which can reduce cross-domain invocations cost below thecurrent cost of kernel invocations by exploiting properties that kernel-lessoperating systems have with respect to robustness, extensibility, security, andperformance. The first three of these properties are generally accepted asbenefits of the kernel-less approach. One of the primary contributions of thiswork is to achieve these benefits while also achieving gains in performance.