The Elmwood Multiprocessor Operating System

Thomas J. LeBlanc, John M. Mellor-Crummey, Neal M. Gafter, Lawrence A. Crowl, and Peter C. Dibble, " The Elmwood Multiprocessor Operating System", Software---Practice and Experience 19(11): 1029-1055, November 1989

Elmwood is an object-oriented, multiprocessor operating system designed and implemented during a graduate seminar. It consists of a minimal kernel and a collection of user-implemented services. The kernel provides two major abstractions: objects, which consist of code and data, and processes, which represent asynchronous activity. Objects, like programs, are passive. To operate on an abstraction or to request a service, processes invoke an entry procedure defined by the corresponding object. Objects implement their own protection and synchronization policies using minimal kernel mechanisms. We describe the Elmwood kernel interface, an implementation on the BBN Butterfly parallel processor, and our experiences in developing a multiprocessor operating system under rigid time constraints. These experiences illustrate several general lessons reguarding kernel design trade-offs for implementation expedience.

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