What to Make of Multicore Processors for Reliable Real-Time Systems?

Now that multicore microprocessors have become a commodity, it is natural to think about employing them in all kinds of computing, including high-reliability embedded real-time systems. Appealing aspects of this development include the ability to process more instructions per second and more instructions per watt. However, not all problems are amenable to parallel decomposition, and for those that are, designing a correct scalable solution can be difficult. If there are deadlines or other hard timing constraints the difficulty becomes much greater. This paper reviews some of what is known about multiprocessor scheduling of task systems with deadlines, including recent advances in the analysis of arbitrary sporadic task systems under fixed-priority and earliest-deadline first scheduling polices. It also examines critically the foundations of these theoretical results, including assumptions about task independence and worst-case execution time estimates, with a view toward their practical applicability.

A PTAS for Static Priority Real-Time Scheduling with Resource Augmentation

We present a polynomial time approximation scheme for the real-time scheduling problem with fixed priorities when resource augmentation is allowed. For a fixed ε>0, our algorithm computes an assignment using at most (1+ε)·OPT+1 processors in polynomial time, which is feasible if the processors have speed 1+ε. We also show that, unless P = NP, there does not exist an asymptotic FPTAS for this problem