On the Soft Real-Time Optimality of Global EDF on Multiprocessors: From Identical to Uniform Heterogeneous

Under the definition of soft real-time (SRT) correctness that requires deadline tardiness to be bounded, both the pre-emptive and non-pre-emptive global EDF (GEDF) schedulers are known to be SRT-optimal on identical multiprocessors. This paper considers the potential extension of these results to uniform heterogeneous multiprocessors. In the pre-emptive case, it is shown that such an extension is possible for two-processor platforms but unlikely for platforms of more than two processors, unless fundamentally new proof techniques are developed. In the non-pre-emptive case, it is shown that no work-conserving scheduler, including GEDF, can be SRT-optimal on uniform multiprocessors, even if the number of processors is limited to two.