Towards exploiting the preservation strategy of sporadic servers

Worst-case response time analysis of hard real-time tasks under hierarchical fixed priority pre-emptive scheduling has been addressed in a number of papers. By means of an example, we show that the existing analysis can be improved when a sporadic server is applied at highest priority and that server is exclusively used for hard real-time tasks. Improving the analysis is not straightforward, however, because the worst-case response time of a task is not necessarily assumed for the first job when released at a critical instant. Moreover, our example illustrates that the provision of the capacity of the server may be fragmented. The paper includes a brief investigation of best-case response times and response jitter for the example