Shielded Processors: Guaranteeing Sub-millisecond Response in Standard Linux

There has been significant progress making standard Linux into a more responsive system for real-time applications. The low latency patches and the preemption patches have allowed guarantees on worst case interrupt response time at slightly above a millisecond. These guarantees today are only met when there is no networking or graphics activity in the system. The shielded processor concept dedicates selected processors in a symmetric multiprocessing system for the real-time components of an application. This paper will describe the implementation of shielded processors in RedHawk Linux and the benefits of shielded processors. It will also present the results of benchmarks for both interrupt response and program execution determinism. Interrupt response time guarantees are significantly below one millisecond and can be guaranteed even in the presence of networking and graphics activity.