Real-time disk scheduling for multimedia applications with deadline-modification-scan scheme

Real-time disk scheduling (RTDS) is important for time-critical multimedia applications. In conventional approaches of real-time disk scheduling, such as SCAN-EDF, the seek-optimizing SCAN scheme is applied to reduce the disk service time of the real-time EDF schedule. Since only tasks with the same deadline are seek-optimized, the obtained improvement of SCAN-EDF is limit ed. In this paper, based on the maximum-scannable-group (MSG) concept, a de adline-modification-scan (DMS or DM-SCAN) algorithm is proposed. Our algori thm uses MSG to automatically decide the suitable task groups for seek-opti mizing. Based on the MSG concept, we repeatedly apply DMS to further increa se disk throughput to support more tasks. We have implemented the proposed algorithm on UnixWare 2.01. The appropriate problem behaviors and parameter values to yield good solutions are investigated. Experiments show that DMS is better than conventional approaches in both the obtained disk throughpu t and the supported tasks. Moreover, our proposed approach can schedule tas k sets that are not schedulable by EDF and SCAN-EDF.