Real-time scheduling on multithreaded processors

This paper investigates real-time scheduling algorithms on upcoming multithreaded processors. As evaluation testbed we introduce a multithreaded processor kernel which is specifically designed as core processor of a microcontroller or system-on-a-chip. Handling of external realtime events is performed through multithreading. Real-time threads are used as interrupt service threads (ISTs) instead of interrupt service routines (ISRs). Our proposed microcontroller supports multiple ISTs with zero-cycle context switching overhead. We investigate the behavior of fixed priority preemptive, earliest deadline first, least laxity first and guaranteed percentage scheduling with respect to multithreaded processors. Our finding is that the strategies GP and LLF result in a good blending of instructions of different threads thus enabling a multithreaded processor to utilize latencies best. Assuming a zero-cycle context switch LLF performs best, however implementation cost are prohibitive.