A Time-Composable Operating System for the Patmos Processor

In the last couple of decades we have witnessed a steady growth in the complexity and widespread of real-time systems. In order to master the rising complexity in the timing behaviour of those systems, rightful attention has been given to the development of time-predictable computer architectures. The Patmos time-predictable microprocessor used in the T-CREST project employs performance-enhancing hardware while keeping the system analyzable. Time composability, at both hardware and software level, is a considerable aid to reducing the integration costs of complex applications. A time-composable operating system, on top of a time-composable processor, facilitates incremental development, which is highly desirable for industry. This paper makes a twofold contribution. First, we present enhancements to the Patmos processor to allow achieving time composability at the operating system level. Second, we extend an existing time-composable operating system, TiCOS, to make best use of advanced Patmos hardware features in the pursuit of time composability.