Real-Time Java™ Platform Programming

Problems with Priority Scheduling

Priorities can be a good scheduling paradigm if they are not loaded with meaning beyond their design. A task with higher priority will be given preference over lower-priority tasks when competing for system resources. If a system has to update a status display, log historical information, and control the feed rate into a band saw, the priority assignments are clear:

Control	high
Display	medium
Logging	low

The intuition here is that seriously bad things happen if the control function does not complete on time, that it is inconvenient if the status display is sluggish, and that there is no harm at all if the logging function runs late. The priority attribute expresses how important activities are, nothing about ...