|
We consider the problem of OS resource management for real- time and multimedia systems where multiple activities with different timing constraints must be scheduled concurrently. Time on a particular resource is shared among its users and must be globally managed in real-time and multimedia systems. A resource kernel is meant for use in such systems and is defined to be one which provides timely, guaranteed and protected access to system resources. The resource kernel allows applications to specify only their resource demands leaving the kernel to satisfy those demands using hidden resource management schemes. This separation of resource specification from resource management allows OS-subsystem- specific customization by extending, optimizing or even replacing resource management schemes. As a result, this resource-centric approach can be implemented with any of several different resource management schemes. We identify the specific goals of a resource kernel: applications must be able to explicitly state their timeliness requirements; the kernel must enforce maximum resource usage by applications; the kernel must support high utilization of system resources; and an application must be able to access different system resources simultaneously. Since the same application consumes a different amount of time on different platforms, the resource kernel must allow such resource consumption times to be portable across platforms, and to be automatically calibrated. Our resource management scheme is based on resource reservation and satisfies these goals. The scheme is not only simple but captures a wide range of solutions developed by the real-time systems community over several years. One potentially serious problem that any resource management scheme must address is that of allowing access to multiple resources simultaneously and in timely fashion, a problem which is known to be NP-complete. We show that this problem of simultaneous access to multiple resources can be practically addressed by resource decoupling and resolving critical resource dependencies immediately. Finally, we demonstrate our resource kernel's functionality and flexibility in the context of multimedia applications which need processor cycles and/or disk bandwidth.
|
