Abstract
Zero-laxity (ZL) and contention-free (CF) policies have received considerable attention owing to their simplicity and applicability to real-time systems equipped with symmetry multiprocessors. Recently, the ZL policy for mixed-criticality (MC) systems has been proposed and studied, but the applicability to and performance of the CF policy for MC systems have not been investigated yet. In this paper, we propose the CF policy (as a scheduling policy) for MC symmetry multiprocessor systems, referred to as the MC systems tailored CF policy (MC-CF), and a schedulability analysis in support thereof. We define the notion of contention-free slots for two different criticalities (of MC systems) of tasks, propose a technique to limit the amount to be utilized for each task by defining an upper bound, and subsequently explain the way in which the contention-free slots are systematically utilized to improve the schedulability of MC symmetry multiprocessor systems. Following this, we develop a deadline analysis (DA) for MC-CF. Using our experimental results under various environmental settings, we demonstrate that MC-CF can significantly improve the schedulability of fixed-priority scheduling.
Highlights
Real-time embedded systems differ from general-purpose systems in that designated multiple real-time tasks are repeatedly executed on limited computing resources (e.g., CPU and memory)
We randomly generates task sets with various input factors; we measure the number of task sets deemed schedulable by deadline analysis (DA) designed for rate monotonic (RM), RM with MC systems tailored CF policy (MC-CF), earliest deadline first (EDF) and EDF with MC-CF
We propose MC-CF for MC multiprocessor systems and MC-CF tailored schedulability analysis to support it
Summary
Real-time embedded systems differ from general-purpose systems in that designated multiple real-time tasks (e.g., engine control and sensing) are repeatedly executed on limited computing resources (e.g., CPU and memory). Real-time tasks need to be conducted within a predefined time, known as a deadline, as a strict design requirement To achieve this goal and considering the characteristics of embedded systems, the following two problems have been extensively studied by the real-time systems community: (i) ways to effectively allocate the limited computing resources to real-time tasks and (ii) approaches to judge whether the system satisfies the design requirement. We define the notion of contention-free slots for two different criticalities (of MC systems) of tasks, propose a technique to restrict the amount to be utilized for each task by defining an upper bound, and present the way in which the contention-free slots are systematically utilized to improve the schedulability of MC multiprocessor systems.
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