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

Rotenberg虚拟简单架构（VISA）：超越安全实时系统的复杂性限制摘要该项目解决了嵌入式系统中一个长期存在的问题：在当代处理器上限制任务的最坏情况执行时间（WCET）。WCET对于实时调度是必不可少的，但对于当代处理器来说，获得它们是棘手的。虚拟简单架构（VISA）框架将任务的WCET绑定负担部分转移到硬件上。VISA是假设的简单处理器的流水线定时规范。WCET是为假设VISA的任务导出的。在运行时，任务在不安全的复杂处理器上推测性地执行，并且其进度被连续地测量。如果继续的安全进程似乎处于危险之中，则复杂处理器被重新配置为直接实现VISA的简单操作模式，从而通过WCET明确地限制任务的总执行时间。VISA提供了用于在不安全处理器上安全操作的通用框架，为在嵌入式系统中开发更高的性能提供了新的机会。该项目预期并有助于计算领域的重大转变（每十年发生一次的那种），从而有助于保持国家在这一领域的领导地位。计算机总是通过将更高级别的复杂性和性能集成到更小的系统中来发展。在20世纪90年代，这种演变导致了具有超级计算机般性能的高功能个人计算机（PC）。现在，在后PC时代，用户与嵌入式计算机连续地、透明地并且真实的时间地交互（例如，蜂窝电话、汽车、飞机、电器、工业/军事应用等）。该项目从根本上提高了嵌入式系统的性能、功能和可靠性，这对我们社会的日常运作至关重要。

RotenbergVirtual Simple Architecture (VISA): Exceeding the Complexity Limit in Safe Real-Time SystemsAbstractThis 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.