A Flexible External Paging Interface

In this paper we describe an aspect of the Spring virtual memory system that was influenced by the distributed object-oriented architecture of Spring. The virtual memory system supports external pagers like those provided in MACH, yet the architecture is more flexible and provides better caching opportunities than is possible in other systems. A novel aspect of the architecture is the separation of the memory abstraction from the interface that provides the paging operations. This separation provides considerable caching opportunities in our file system and it facilitates our extensible stackable file system architecture. The virtual memory architecture described in this paper is implemented and has been in use for over three years as part of the experimental Spring operating system.