Nonmigratory online deadline scheduling on multiprocessors
In this paper we consider multiprocessor scheduling with hard deadlines and investigate the cost of eliminating migration in the online setting. Let I be any set of jobs that can be completed by some migratory offline schedule on m processors. We show that I can also be completed by a nonmigratory online schedule using m speed-5.828 processors (i.e., processors 5.828 times faster). This result supplements the previous results that I can also be completed by a nonmigratory offline schedule using 6m unit-speed processors [ B. Kalyanasundaram and K. R. Pruhs, J. Algorithms, 38 ( 2001), pp. 2 - 24] or a migratory online schedule using m speed-2 processors [ C. A. Phillips et al., Algorithmica, 32 ( 2002), pp. 163 - 200]. Our result is based on a simple conservative scheduling algorithm called PARK, which commits a processor to a job only when the processor has zero commitment before its deadline. A careful analysis of PARK further shows that the processor speed can be reduced arbitrarily close to 1 by exploiting more processors ( say, using 16m speed-1.8 processors). PARK also finds application in overloaded systems; it gives the first online nonmigratory algorithm that can exploit moderately faster processors to match the performance of any migratory offline algorithm.
multiprocessor scheduling online algorithms competitive analysis resource augmentation job migration