SVR4 UNIX Scheduler Unacceptable for Multimedia Applications

Jason Nieh, James G. Hanko, J. Duane Northcutt, Gerard A. Wall

Proceedings of the 4th International Workshop on Network and Operating System Support for Digital Audio and Video, Lancaster, UK, November 3-5, 1993, pp. 35-48


Applications that manipulate digital audio and video are rapidly being added to workstations. Such computations can often consume the resources of an entire machine. By incorporating a “realtime” process scheduler, UNIX System V Release 4 (SVR4), the most common basis of workstation operating systems, claims to provide system support for multimedia applications. Our quantitative measurements of real application performance demonstrate that this process scheduler is largely ineffective and can even produce system lockup. While SVR4 UNIX provides many controls for changing scheduler performance, they are virtually impossible to use successfully. Furthermore, the existence of a realtime static priority process scheduler in no way allows a user to deal with these problems. This paper provides a quantitative analysis of real system behavior, demonstrates why it is not possible to obtain the kind of behavior desired with the mechanisms currently provided by the system, and presents modifications to improve the situation.



Columbia University Department of Computer Science