The problem of scheduling multiple streams of real-time customers is addressed in this paper. The paper rst introduces the notion of (m; k)-rm deadlines to better characterize the timing constraints of real-time streams. More speci cally, a stream is said to have (m; k)-rm deadlines if at least m out of any k consecutive customers must meet their deadlines. A stream with (m; k)-rm deadlines experiences a dynamic failure if fewer than m out of any k consecutive customers meet their deadlines. The paper then proposes a priority-based policy for scheduling N such streams on a single server to reduce the probability of dynamic failure. The basic idea is to assign higher priorities to customers from streams that are closer to a dynamic failure so as to improve their chances of meeting their deadlines. The paper proposes a heuristic for assigning these priorities. The e ectiveness of this approach is evaluated through simulation under various customer arrival and service patterns. The scheme is compared to a conventional scheme where all customers are serviced at the same priority level and to an imprecise computation model approach. The evaluation shows that substantial reductions in the probability of dynamic failure are achieved when the proposed policy is used.
The (m,k)-firm model REF is used in a degraded mode to better characterize the timing constraints of real-time streams.
A Dynamic Priority Assignment Technique for Streams with (m,k)-Firm Deadlines
IEEE Transactions on Computers
Computer Science