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Open AccessArticle

Online Slack-Stealing Scheduling with Modified laEDF in Real-Time Systems

Agency for Defense Development, P.O. Box 35, Yuseong, Daejeon 34134, Korea
School of Electronic Engineering, Kumoh National Institute of Technology, 61 Daehak-ro, Gumi, Gyeongbuk 39177, Korea
Department of Computer Science & Engineering, ChungNam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Korea
Author to whom correspondence should be addressed.
Electronics 2019, 8(11), 1286;
Received: 11 October 2019 / Revised: 28 October 2019 / Accepted: 30 October 2019 / Published: 5 November 2019
(This article belongs to the Section Computer Science & Engineering)
In hard real-time task systems where periodic and aperiodic tasks coexist, the object of task scheduling is to reduce the response time of the aperiodic tasks while meeting the deadline of periodic tasks. Total bandwidth server (TBS) and advanced TBS (ATBS) are used in dynamic priority systems. However, these methods are not optimal solutions because they use the worst-case execution time (WCET) or the estimation value of the actual execution time of the aperiodic tasks. This paper presents an online slack-stealing algorithm called SSML that can make significant response time reducing by modification of look-ahead earliest deadline first (laEDF) algorithm as the slack computation method. While the conventional slack-stealing method has a disadvantage that the slack amount of each frame must be calculated in advance, SSML calculates the slack when aperiodic tasks arrive. Our simulation results show that SSML outperforms the existing TBS based algorithms when the periodic task utilization is higher than 60%. Compared to ATBS with virtual release advancing (VRA), the proposed algorithm can reduce the response time up to about 75%. The performance advantage becomes much larger as the utilization increases. Moreover, it shows a small performance variation of response time for various task environments. View Full-Text
Keywords: SSML; slack computation; aperiodic task scheduling; mixed task system; slack-stealing SSML; slack computation; aperiodic task scheduling; mixed task system; slack-stealing
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Jeon, W.; Kim, W.; Lee, H.; Lee, C.-H. Online Slack-Stealing Scheduling with Modified laEDF in Real-Time Systems. Electronics 2019, 8, 1286.

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