Coordinated CPU and Event Scheduling for Distributed Multimedia Applications

Distributed multimedia applications require support from the underlying operating system to achieve and maintain their desired Quality of Service (QoS). This has led to the creation of novel task and message schedulers and to the development of QoS mechanisms that allow applications to explicitly interact with relevant operating system services. However, the task scheduling techniques developed to date are not well equipped to take advantage of such interactions. As a result, important events such as position update messages in virtual environments may be ignored. If a CPU scheduler ignores these events, players will experience a lack of responsiveness or even inconsistencies in the virtual world. This paper argues that real-time and multimedia applications can benefit from coordinated schemes for CPU and event scheduling and we describe a novel event delivery mechanism, termed ECalls, that supports such coordination. We then use ECalls to reduce variations in inter-frame times for media streams, and to reduce event response times for real-time applications like distributed virtual worlds