Providing QoS to Legacy Multimedia Applications

Millions of applications have been developed on conventional time-sharing systems. We call those applications legacy applications. Many of them, typically multimedia applications, have Quality of Service (QoS) demands, which are not supported in time-sharing systems. Although many scheduling algorithms and schedulers have been proposed to schedule multimedia applications, it is not feasible to rebuild millions of legacy multimedia applications in a completely new programming model. Moreover, the execution pattern of multimedia applications is difficult to predict.

This project is developing a legacy application-compatible, adaptation-oriented scheduling framework. The new scheduler is implemented as a Linux loadable module. Thus users can either use the original Linux scheduler or use our scheduler by loading the module. In the new scheduler, users can reserve a default execution rate for legacy multimedia applications, and a rate adjustment mechanism is provided for adaptation.

The framework supports our new variable-rate execution (VRE) tasks as well as the more static rate-based execution (RBE) tasks, traditional periodic tasks that run at a constant rate, and non-real-time requests that have no QoS demand.