Tests for global EDF schedulability analysis

Abstract

Several schedulability tests have been proposed for global EDF scheduling on identical multiprocessors. All these tests are sufficient, rather than exact. These different tests were, for the most part, independently developed. The relationships among such tests have not been adequately investigated, so that it is difficult to understand which test is most appropriate in a particular given scenario. This paper represents an attempt to remedy this, by means of three major contributions. First, we summarize the main existing results for the schedulability analysis of multiprocessor systems scheduled with global edf, showing, when possible, existing dominance relations. We compare these algorithms taking into consideration different aspects, namely, run-time complexity, average performances over randomly generated workloads, sustainability properties and speedup factors. Second, based on this comparative evaluation we propose a recommended approach to schedulability analysis, that suggests a particular order in which to apply preexisting tests, thereby accomplishing both good provable performance and good behavior in practice. And finally, we propose a further improvement to one of these preexisting tests to improve its run-time performance by an order of magnitude, while completely retaining its ability to correctly identify schedulable systems.