Generic virtual memory management for operating system kernels

Abstract

We discuss the rationale and design of a Generic Memory management Interface, for a family of scalable operating systems. It consists of a general interface for managing virtual memory, independently of the underlying hardware architecture (e.g. paged versus segmented memory), and independently of the operating syst.em kernel in which it is to be integrated.In particular, this iuterface provides abstractions for support of a single, consistent cache for both mapped objects and explicit I/O, and control of data caching in real memory. Data management policies are delegated to external managers.A portable implementation of the Generic Memory management Interface for paged architectures, the Paged Virtual Memory manager, is detailed. The PVM uses the novel history object technique for efficient deferred copying. The GM1 is used by the Chorus Nucleus, in particular to support a distributed version of Unix.Performance measurements compare favorably with other systems.The Chorus" architecture is designed to support new generations of open, distributed, scalable operating systems. It allows the integration of various families of operating systems, ranging from small real-time systems to general-purpose operating systems, in a single distributed environment.The Chorus architecture is based on a minimal realtime Nucleus that integrates distributed processing and communication at the lowest level. Chorus opera.ting systems are built as sets of independent system servers, that rely on the basic, generic services provided by the Nucleus, i.e. thread scheduling, network transparent IPC, virtual memory management and real-time event handling.

The new structure of an operating system

“…Recently, Mach [5] and Chorus [1] introduce user-level virtual memory management as an external pager. Using an external pager approach enables us to write a code for an application specific policy for memory management.…”