A dynamic scheduler for real-time periodic tasks with quality of service requirements
Maryline Chetto, Audrey Marchand · 2006
Abstract:- This paper is concerned with dynamic scheduling in overload real-time systems that have Quality of Service requirements. We assume that tasks are periodic and may miss their deadlines, occasionally, as defined by the so-called Skip-Over model. Every task is characterized by a skip factor which represents the minimal Quality of Service (QoS) level, required by the concerned application. The objective consists in scheduling tasks in order to guarantee the QoS constraint and maximize the ratio of periodic task instances which complete before their deadline. A comparative evaluation of scheduling algorithms can then be realized by measuring this ratio. In this paper, we present a dynamic scheduling algorithm, called RLP (Red as Late as possible) based on the EDL (Earliest Deadline as Late as possible) strategy. Simulation results are reported in order to show performance improvement obtained by RLP, in comparison with the two classical skip-over algorithms, namely RTO and BWP, introduced about ten years ago.