Describing the Operating System for Accurate User-mode Simulation

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

This is an EAGER project that addresses a highly exploratory investigation into key elements needed to specify the characteristics of an operating system (OS) in a way that permits an architectural model to be created that interacts fully with a suite of simulation tools. The suite of tools, CoGenT (CoGeneration of Tools), include specification languages to allow researchers to express novel instruction sets and micro-architectures and the infrastructure for automatic generation of corresponding functional and timing co-simulators, compilers, linkers, loaders, debuggers, assemblers, disassemblers, and a fully integrated instrumentation facility to enable meaningful experimentation within this new design space. CoGenT?s ability to automatically generate a functional simulator from a specification, and other related elements, will be released this year. This EAGER addresses the problem that, in simulating complex architectures, it is important to be able to specify OS support, not just as a set of external calls, but as a specific model that integrates with the rest of the architecture. Current architectures rely on the services and policies of the operating system, and the operating system itself needs to evolve with the radical shifts in architecture and applications that are anticipated in the next decade. With this project, this team develops an approach that enables simultaneous research into novel hardware and software paradigms, with great flexibility, and without the heretofore prohibitive cost of manually building a complete hardware and software simulation infrastructure with a tailored OS implementation. Traditional system simulation approaches either ignored OS impact on performance or resorted to costly and inflexible full system simulation where an actual OS implementation is executed directly. The former provides unrealistic results, and the latter does not admit the kind of exploration needed for transformative paradigm shifts. The goal of this project is to extend the relatively recent approach of functional and timing co-simulation for hardware architectures into "pseudo-full system simulation", where the OS becomes a first-class element in the simulation modeling and instrumentation framework. Simulating an OS model derived from a specification will also enable sensitivity and significance analyses, often neglected in current simulation-based research even though they are essential to understanding the real impact of new approaches.