Guest Editorial: A Review of Worst-Case Execution-Time Analysis

A development process for safety-critical real-time computer systems has to emphasize the importance of time. On the one hand, such a development process has to be based on hardware and software technology that supports predictability in the time domain. On the other hand, the development process has to provide tools for assessing and verifying the correctness of the timing of both the hardware and the software components of the real-time systems being developed. Together with schedulability analysis, Worst-case execution time analysis (WCET analysis) forms the basis for establishing confidence into the timely operation of a real-time system. WCET analysis does so by computing (upper) bounds for the execution times of the tasks in the system. These bounds are needed for allocating the correct CPU time to the tasks of an application. They form the inputs for schedulability tools, which test whether a given task set is schedulable (and will thus meet the timing requirements of the application) on a given target system. While schedulability analysis is one of the traditional fields of investigation in real-time systems research, WCET analysis caught the attention of the research community only about ten years ago (Kligerman and Stoyenko, 1986; Mok et al., 1989; Puschner and Koza, 1989; Shaw, 1989). In the last decade, however, more and more research groups started to put a focus on WCET analysis. As a result, substantial progress has been made in this area in a relatively short time. After ten years of research in the field, it is appropriate to have a special issue on WCET analysis. It is the goal of this special issue to review the achievements in WCET analysis and to report about the recent advances in this field. In the following section we will define the problem area of WCET analysis and thus clarify the issue WCET analysis is dealing with— still many people mix up execution-time analysis and response-time analysis. We will then summarize the subproblems of WCET analysis and provide an overview of previous contributions to the state of the art in this field. At the end of the introduction we will give an overview to the research papers that have been selected for this special issue.

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