Enhancing Parallel Multimedia Servers through New Hierarchical Disk Scheduling Algorithms
VECPAR '00 Selected Papers and Invited Talks from the 4th International Conference on Vector and Parallel Processing
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-------- An integrated platform which is capable of meeting the requirements of both traditional real-time control processing and multimedia processing has enormous potential for accommodating various kinds of new applications. However, except for the simplest of situations, few, if any, research or commercial systems successfully provide architectural and OS mechanisms which can efficiently support both hard real-time computation and multimedia soft real-time computation. In this paper, we propose a multimedia server executing on multiprocessor real-time operating systems to provide different classes of guarantee to support both types of processing. The multimedia server supports multiple periodic multimedia streams with a capability for graceful QoS degradation during system overload. In this paper we (i) discuss realistic system implementation issues on the SGI IRIX/REACT/PRO operating system, (ii) develop several multimedia server scheduling algorithms, and (iii) present a performance evaluation. We chose the SGI system as an implementation platform because it is being used more and more for multimedia applications. Our performance evaluation demonstrates that a multimedia server algorithm based on a flexible, proportional allocation scheme provides the best performance and that simple iterative scheduling is adequate for handling graceful degradation of the multimedia streams. We consider issues such as server size and period as well as the impact of context switch overhead on the performance. We also show that for applications which require integrated resource sharing, neither the frame scheduler nor the deadline scheduler supplied in the IRIX/REACT/PRO OS are suitable. We propose an implementation solution that is appropriate.