Machine-independent Virtual Memory Management for Paged Uniprocessor And

We describe the facilities provided by PLATINUM, a multiprocessor micro-kernel, to support user-level exception handling. The principal design goal for these facilities is to provide a very simple mechanism with su cient exibility and e ciency to experiment with the implementation of a wide variety of exception-driven, user-level services in a parallel system. These services provide conventional exception handling, an interface between parallel programs and debugging or performance monitoring tools, user-level paging and I/O services, and support for user-level lightweight process packages. The exception handling facility is based on fast message passing using a recon gurable hierarchy of mailboxes. The mechanisms we describe have performance comparable to their uniprocessor signal handling under Unix, and retain that performance when used on a multiprocessor to support the kind of exception-driven services demanded by a parallel programming environment. 1 Flexible Exception Handling on Multiprocessors The practice of structuring an operating system as a relatively small kernel (popularly called a \micro-kernel") augmented by a collection of server processes continues to be an active topic of research [Ras86, Mul87]. Although the modularity of this approach yields software engineering advantages such as improved comprehensibility, ease of maintenance, and reliability, the increased number of inter-module control transfers in such a system can put it at a performance disadvantage with respect to more monolithic designs[ALBL91]. On a multiprocessor, however, the modularity of the micro-kernel approach can be exploited to take advantage of parallelism by replicating and distributing servers across multiple processors. Because many operating system services are exception-driven, we address the issue of providing a kernel-de ned facility to support modular and e cient exception handling in a multiprocessor micro-kernel system. In this paper we present a set of requirements for such facilities, a description of our solution to the problem, an evaluation of that solution, and a discussion of remaining problems and directions for future research. The combination of the micro-kernel design and the emphasis on logical and physical parallelism requires exception handling that is exible, e cient, and allows maximum parallelism on a multiprocessor. Some of the many potential applications for user-level exception handling on a multiprocessor include: 1. Providing an error recovery and/or cleanup mechanism, This material is based upon work supported by the National Science Foundation under Grant number CDA8822724. The Government has certain rights in this material. To appear in Proceedings of SEDMS-III, Newport Beach, CA. March 1992.