Finding Response Times in a Real-Time System

There are two major performance issues in a real-time system where a processor has a set of devices connected to it at different priority levels. The first is to prove whether, for a given assignment of devices to priority levels, the system can handle its peak processing load without losing any inputs from the devices. The second is to determine the response time for each device. There may be several ways of assigning the devices to priority levels so that the peak processing load is met, but only some (or perhaps none) of these ways will also meet the response-time requirements for the devices. In this paper, we define a condition that must be met to handle the peak processing load and describe how exact worst-case response times can then be found. When the condition cannot be met, we show how the addition of buffers for inputs can be useful. Finally, we discuss the use of multiple processors in systems for real-time applications.