IMPLEMENTATION OF A TIME-DRIVEN SCHEDULER FOR REAL-TIME OPERATING SYSTEMS.

In the time-driven scheduling (TDS) model, both the importance value and timing criticality of each task are given together as a function of time. The TDS scheduler attempts to maximize the total value of completed tasks. A practical TDS model that has been implemented in the Mach operating system kernel is described. Some of the important design considerations for a flexible TDS scheduler are discussed, with emphasis on policy/mechanism separation as a system structuring principle. The structure of a TDS scheduler that was actually implemented is explained. The practicality of the TDS scheduler is demonstrated by performance results.