New paper for pre-review

Separation of concerns for resilient embedded real-time

Abstract:

Many embedded applications, specifically safety-critical ones, have strict real-time constraints. In the very worst case, missing a deadline can be catastrophic. Therefore, many approaches have been developed and successfully deployed whereby time is explicitly used to schedule the application tasks. A very important design paramater is a guaranteed Worst Case Execution Time (WCET). While this approach can be justified partly for historical reasons but also for reasons of simplicity, modern many-core processors pose a significant challenge as the chips combine multiple tightly coupled processing cores, fast caches to alleviate slow memory and complex peripherals. All these elements result in a statistical execution behaviour whereby a measure like WCET is no longer practical. In this paper we advocate that this situation requires a different approach to programming, i.e. one based on events and concurrency with time no longer being a strict design parameter but rather a consequence of the program execution. It is a consequence of applying a separation of concerns to execution in space and time. Benchmarks obtained with the latest version of VirtuosoNext Designer, a fine-grain partitioning multi-core RTOS, illustrate that this is not only feasible but also with no compromise on the real-time behavior. In the latest implementation this was extended to real-time fault recovery making systems much more resilient than with the traditional approach.