The workload on computers is rapidly changing. In the past, computers were used in automating tasks around the work place, such as word and accounts processing in offices, and design automation in engineering environments. The human-computer interface has been primarily textual, with some limited amount of graphical input and display. With the phenomenal improvement in hardware technology in recent years, even highly affordable personal computers are capable of supporting much richer interfaces. Images, video, audio, and
interactive graphics have become common place. A growing number of multimedia applications are available, ranging from video games and movie players, to sophisticated distributed simulation and virtual reality environments. In anticipation of a wider adoption of multimedia in applications in the future, there has been much research and development activity in computer architecture for multimedia applications. Not only is there a proliferation of processors that are
built for accelerating the execution of multimedia applications, even general purpose microprocessors have incorporated special instructions to speed their execution
While hardware has advanced to meet the special demands of multimedia applications, software environments have not. In particular, multimedia applications have real-time constraints which are not handled well by today’s general-purpose operating systems. The problems experienced by users of multimedia on these machines include video jitter, poor “lip-synchronization” between audio and video, and slow interactive response while running video applications. Commercial operating systems such as UNIX SVR4 attempt to address these problems by providing a real-time scheduler in addition to a standard time-sharing scheduler. However, such hybrid schemes lead to experimentally demonstrated unacceptable behavior, allowing runaway realtime activities to cause basic system services to lock up, and the user to lose control over the machine .
This paper argues for the need to design a new processor scheduling algorithm that can handle the mix of applications we see today. We present a scheduling algorithm that we have implemented in the Solaris UNIX operating system [Eykholt et al. 1992], and demonstrate its improved performance over existing schedulers in research and practice on real applications. In particular, we have quantitatively compared it against the popular weighted fair queueing and UNIX SVR4 schedulers in supporting multimedia applications in a realistic workstation environment.
