Abstract

There are stringent requirements on the operating system scheduler of a multimedia processor. First, when a user starts a task believing it to be backed by hardware, the system cannot terminate that task. The task must continue to run as if the hardware were present. Second, optimizing the Quality of Service (QOS) requires that tasks use all available system resources. Third, QOS decisions must be made globally, and in the interests of the user, if system overload occurs. No previously existing scheduler meets all these requirements.

The Equator Technologies, Inc. (ETI) Resource Distributor guarantees scheduling for admitted tasks: the delivery of resources is not interrupted even if the system is overloaded. The Scheduler delivers resources to applications in units known to be useful for achieving a specific level of service quality. This promotes better utilization of system resources and a higher perceived QOS. When QOS degradations are required, the Resource Distributor never makes inadvertent or implicit policy decisions: policy must be explicitly specified by the user.

While providing superior services for periodic real-time applications, the Resource Distributor also guarantees liveness for applications that are not real-time. Support for real-time applications that do not require continuous resource use is integrated: it neither interferes with the scheduling guarantees of other applications nor ties up resources that could be used by other applications.

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