Angel: A proposed multiprocessor operating system kernel

We describe an operating system design for multiprocessor systems called Angel, based on a single, coherent, uniform virtual address space. This unies naming and interprocess communication in both shared and distributed memory multiprocessors by using distributed shared memory techniques when shared memory is not already provided by the hardware. The design is motivated by analysis of our earlier operating system implementation, based on message passing, and we show how the uniform address space attempts to solve problems with that approach. In particular, we consider the use of client-server cross-mapping to optimise interprocess communications, as used in Bershad et al.'s lightweight RPC. This document describes initial motivations for Angel and subsequent detailed design| we will review and may modify many of the details described as the design progresses.