Speed is as powerful as clairvoyance

Abstract

We introduce resource augmentation as a method for analyzing online scheduling problems. In resource augmentation analysis the on-line scheduler is given more resources, say faster processors or more processors, than the adversary. We apply this analysis to two well-known on-line scheduling problems, the classic uniprocessor CPU scheduling problem l|rf, pmtn\S. F and the best-effort firm real-time scheduling problem l\r, pmtn\2 iv((l -I/,-). It is known that there are no constant competitive nonclairvoyant on-line algorithms for these problems. We show that there are simple on-line scheduling algorithms for these problems that are constant competitive if the online scheduler is equipped with a slightly faster processor than the adversary. Thus, a moderate increase in processor speed effectively gives the on-line scheduler the power of clairvoyance. Furthermore, the on-line scheduler can be constant competitive on all inputs that are not closely correlated with processor speed. We also show that the performance of an on-line scheduler in best-effort real time scheduling can be significantly improved if the system is designed in such a way that the laxity of every job is proportional to its length. © 2000 ACM.