The schedulability region of two-level mixed-criticality systems based on EDF-VD

The algorithm Earliest Deadline First with Virtual Deadlines (EDF-VD) was recently proposed to schedule mixed-criticality task sets consisting of high-criticality (HI) and low-criticality (LO) tasks. EDF-VD distinguishes between HI and LO mode. In HI mode, the HI tasks may require executing for longer than in LO mode. As a result, in LO mode, EDF-VD assigns virtual deadlines to HI tasks (i.e., it uniformly downscales deadlines of HI tasks) to account for an increase of workload in HI mode. Different schedulability conditions have been proposed in the literature; however, the schedulability region to fully characterize EDF-VD has not been investigated so far. In this paper, we review EDF-VD's schedulability criteria and determine its schedulability region to better understand and design mixed-criticality systems. Based on this result, we show that EDF-VD has a schedulability region being around 85% larger than that of the Worst-Case Reservations (WCR) approach.