Analysis on Scheduling Algorithms of Real-Time Hybrid Tasks

2014 ◽  
Vol 644-650 ◽  
pp. 2253-2257
Author(s):  
Jian Lang Wu ◽  
Jing Kai Shi ◽  
Yi Bin Wang
Keyword(s):  
Real Time ◽  
Earliest Deadline First ◽  
Real Time Systems ◽  
Extended Version ◽  
Periodic Tasks ◽  
Aperiodic Tasks ◽  
Hard Real Time ◽  
Uniprocessor Systems ◽  
Time Systems ◽  
Earliest Deadline

In real-time systems, periodic tasks and aperiodic tasks exist simultaneously. In a uniprocessor system, mainly there are Deferrable Server algorithm (DS) [1], Slack Stealing algorithm (SSA) [2] and their extended version for software/hardware hybrid real-time task scheduling. DS algorithm sets a high priority periodic task server to provide services for aperiodic tasks, while SSA algorithm computes tasks unoccupied time offline, and then schedule aperiodic tasks during the unoccupied period. The two algorithms are both proposed for soft real-time tasks, reducing the response time of the real-time tasks, but cannot guarantee that these aperiodic real-time tasks received can meet deadlines. In this paper, through combination of DS algorithm and EDF (Earliest Deadline First) algorithm [6], a new algorithm called DS-EDF is introduced, which can scheduling hard real-time aperiodic tasks on the DS server. This algorithm is not only suitable for uniprocessor systems, but also has the ability to extend to multiprocessor systems.

Energy efficient fault-tolerant earliest deadline first scheduling for hard real-time systems

2014 ◽  
Vol 50 (5-6) ◽  
pp. 592-619 ◽  
Author(s):  
Qiushi Han ◽  
Linwei Niu ◽  
Gang Quan ◽  
Shaolei Ren ◽  
Shangping Ren
Keyword(s):  
Real Time ◽  
Energy Efficient ◽  
Fault Tolerant ◽  
Earliest Deadline First ◽  
Real Time Systems ◽  
Hard Real Time ◽  
Time Systems ◽  
Earliest Deadline

Energy-Efficient Scheduling for Embedded Real-Time Systems Using Threshold Work-Demand Analysis

2017 ◽  
Vol 26 (06) ◽  
pp. 1750091 ◽  
Author(s):  
Linwei Niu ◽  
Wei Li
Keyword(s):  
Energy Saving ◽  
Real Time ◽  
Energy Efficient ◽  
Critical Speed ◽  
Demand Analysis ◽  
Real Time Systems ◽  
Work Demand ◽  
Hard Real Time ◽  
Time Systems ◽  
Earliest Deadline

In this paper, we study the problem of reducing the energy consumption for hard real-time systems scheduled according to either fixed-priority (FP) or earliest-deadline-first (EDF) scheme. To balance the static and dynamic energy consumptions, the concept of critical speed was proposed in previous research. Moreover, when combined with the processor idle/shutdown state, the critical speed was widely used as the lower bound for voltage scaling in literature. In this paper, we show that this strategy might not always be more energy efficient than the traditional DVS strategy and there exists a dynamic tradeoff between these two strategies depending on the job’s work-demand to be finished within certain intervals. To effectively address this issue, we propose a unified approach that combines these two strategies to achieve better overall energy saving performance. Our approach determines the energy-efficient speeds for real-time jobs in their corresponding feasible intervals based on the threshold work-demand analysis. Our experimental results demonstrate that the proposed techniques significantly outperform previous approaches in the overall energy saving performance.

scholarly journals Scheduling an aperiodic flow within a real-time system using Fairness properties

2014 ◽  
Vol Volume 18, 2014 ◽  
Author(s):  
Annie Choquet-Geniet ◽  
Sadouanouan MALO
Keyword(s):  
Real Time ◽  
Acceptance Test ◽  
Periodic Tasks ◽  
Real Time System ◽  
Model Driven ◽  
Aperiodic Tasks ◽  
International Audience ◽  
Hard Real Time ◽  
Model Driven Approach ◽  
Time Systems

International audience We consider hard real-time systems composed of periodic tasks and of an aperiodic flow. Each task, either periodic or aperiodic, has a firm deadline. An aperiodic task is accepted within the system only if it can be completed before its deadline, without causing temporal failures for the periodic tasks or for the previously accepted aperiodic tasks. We propose an acceptance test, linear in the number of pending accepted aperiodic tasks. This protocol can be used provided the idle slots left by the periodic tasks are fairly distributed. We then propose a model-driven approach, based on Petri nets, to produce schedules with a fair distribution of the idle slots for systems of non independent periodic tasks. Nous considérons des systèmes temps-réel composés de tâches périodiques et d’un fluxapériodique. Toutes les tâches, périodiques comme apériodiques, sont soumises à des échéancesstrictes. Une tâche apériodique n’est acceptée que si elle ne remet pas en cause le respect deséchéances par les tâches périodiques et par les tâches apériodiques déjà acceptées. Nous proposonsun protocole d’acceptation des tâches apériodiques de complexité linéaire en le nombre de tâchesapériodiques acceptées présentes dans le système. Ce protocle est utilisable dès lors que les tempscreux sont répartis de manière équitable. Nous proposons donc une approche modèle, à base deréseaux de Petri, pour produire des séquences où les temps creux sont équitablement répartis, pourdes systèmes de tâches interdépendantes.

Energy harvesting earliest deadline first scheduling algorithm for increasing lifetime of real time systems

2019 ◽  
Vol 118 (4) ◽  
pp. 160
Author(s):  
G. Madhumita ◽  
G. Rajini ◽  
B. Subisha
Keyword(s):  
Energy Consumption ◽  
Energy Harvesting ◽  
Real Time ◽  
Scheduling Algorithm ◽  
Earliest Deadline First ◽  
Real Time Systems ◽  
Tasks Scheduling ◽  
Time Systems ◽  
Earliest Deadline ◽  
Reducing Energy

In this paper, a new approach for energy minimization in energy harvesting real time systems has been investigated. Lifetime of a real time systems is depend upon its battery life.  Energy is a parameter by which the lifetime of system can be enhanced.  To work continuously and successively, energy harvesting is used as a regular source of energy. EDF (Earliest Deadline First) is a traditional real time tasks scheduling algorithm and DVS (Dynamic Voltage Scaling) is used for reducing energy consumption. In this paper, we propose an Energy Harvesting Earliest Deadline First (EH-EDF) scheduling algorithm for increasing lifetime of real time systems using DVS for reducing energy consumption and EDF for tasks scheduling with energy harvesting as regular energy supply. Our experimental results show that the proposed approach perform better to reduce energy consumption and increases the system lifetime as compared with existing approaches.  

A Novel On-Chip Task Scheduler for Mixed-Criticality Real-Time Systems

2019 ◽  
Vol 28 (supp01) ◽  
pp. 1940005 ◽  
Author(s):  
Lukáš Kohútka ◽  
Lukáš Nagy ◽  
Viera Stopjaková
Keyword(s):  
Real Time ◽  
Real Time Systems ◽  
Chip Area ◽  
Hardware Architectures ◽  
On Chip ◽  
Hard Real Time ◽  
Time Systems ◽  
Earliest Deadline ◽  
Novel Design ◽  
Mixed Criticality

This paper presents a novel design of a coprocessor that performs hardware-accelerated task scheduling for embedded real-time systems consisting of mixed-criticality real-time tasks. The proposed solution is based on the Robust Earliest Deadline (RED) algorithm and previously developed hardware architectures used for scheduling of real-time tasks. Thanks to the HW implementation of the scheduler in the form of a coprocessor, the scheduler operations (i.e., instructions) are always completed in two clock cycles regardless of the actual or even maximum task amount within the system. The proposed scheduler was verified using simplified version of UVM and applying billions of randomly generated instructions as inputs to the scheduler. Chip area costs are evaluated by synthesis for Intel FPGA Cyclone V and for 28-nm TSMC ASIC. Three versions of real-time task schedulers were compared: EDF-based scheduler designed for hard real-time tasks only, GED-based scheduler and the proposed RED-based scheduler, which is suitable for tasks of various criticalities. According to the synthesis results, the RED-based scheduler consumes LUTs and occupies larger chip area than the original EDF-based scheduler with equivalent parameters used. However, the RED-based scheduler handles variations of task execution times better, achieves higher CPU utilization and can be used for the scheduling of hard real-time, soft real-time and nonreal-time tasks combined in one system, which is not possible with the former algorithms.

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