Lower Level Architecture of the Sombrero Single Address Space Distributed Operating System

D.S. Miller, D.B. White, A.C. Skousen, and R. Tcherepov (USA)


Single address space operating systems, operating systems, distributed operating systems, object-oriented systems, distributed shared memory


Sombrero is an object-oriented single address space operating system whose virtual address space can be distributed over multiple nodes. This paper presents recent additions to the design and implementation of the lower level architecture of Sombrero. This design exploits Sombrero’s object-oriented development model to provide an implementation of a lower-level architecture for the Alpha platform. Software representations of the hardware system’s major components have been implemented. The existing middle level architectural modules now use the lower-level services. These include board and processor level hardware interfaces as well as interrupt processing, device driver and protocol component architectures. We contrast differences in the ways these things are designed and operate in a single address space environment with the way they are done in a conventional multiple address space operating system. Features covered include the use of passive servers, simple efficient thread switching and threads blocking within interrupts. Passive and active device drivers are described and the rational for each mode given. The performance of the Sombrero protocol stack was closely examined with attention to its passive service architecture and thread switching method. The current Sombrero Prototype is described.

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