Virtual Simple Architecture (VISA): Exceeding the Complexity Limit in Safe Real-Time Systems

North Carolina State University, Raleigh NC

Investigators

Abstract

Rotenberg Virtual Simple Architecture (VISA): Exceeding the Complexity Limit in Safe Real-Time Systems Abstract This project resolves a long-standing problem in embedded systems: bounding the worst-case execution times (WCET) of tasks on contemporary processors. WCETs are essential for real-time scheduling; yet deriving them for contemporary processors is intractable. The Virtual Simple Architecture (VISA) framework shifts the burden of bounding the WCETs of tasks, in part, to hardware. A VISA is the pipeline timing specification of a hypothetical simple processor. WCET is derived for a task assuming the VISA. At run-time, the task is executed speculatively on an unsafe complex processor, and its progress is continuously gauged. If continued safe progress appears to be in jeopardy, the complex processor is reconfigured to a simple mode of operation that directly implements the VISA, thereby explicitly bounding the task's overall execution time by the WCET. VISA provides a general framework for safe operation on unsafe processors, setting up new opportunities for exploiting higher performance in embedded systems. The project anticipates and contributes to a major shift in computing (the kind that occurs once every decade), thus helping to preserve the nation's leadership in this area. Computers have always evolved by integrating higher levels of complexity and performance into smaller systems. In the 1990s, this evolution led to highly functional personal computers (PC) with supercomputer-like performance. Now, in the post-PC era, users interact with embedded computers continuously, transparently, and in real time (e.g., cell phones, cars, airplanes, appliances, industry/military applications, etc.). This project radically increases the performance, functionality, and reliability of embedded systems, which are vital to the day-to-day functioning of our society.