20. Global Dynamic Priority Scheduling

In this chapter, we briefly describe the research that had been conducted in the dynamic-priority scheduling of systems of three-parameter sporadic tasks. In contrast to the situation with respect to Liu and Layland task systems (Chap. 7) where there is a very large body of work to discuss, the research on dynamic priority (DP) scheduling of three-parameter sporadic task systems is rather sparse. The one scheduling algorithm that has been explored in some detail—earliest deadline zero laxity (edzl) (discussed in Sect. 20.2)—is “almost” a fixed job priority (FJP) algorithm in a sense that will become clearer upon reading Sect. 20.2, and hence most of the analyses conducted on edzl are similar to the analyses few have seen in earlier chapters regarding earliest-deadline-first (\(\textsf{EDF}\)).