ER-EDF: A QoS Scheduler for Real-Time Embedded Systems

IEEE Transactions on Industrial Informatics, 2000

We consider a dynamic set of soft real-time applications using a set of shared resources. Each application can execute in different modes, each one associated with a level of Quality of Service (QoS). Resources, in their turn, have different modes, each one with a speed and a power consumption, and are managed by a Reservation Based scheduler enabling a dynamic allocation of the fraction of resources (bandwidth) assigned to each application.

Asian Journal of Research in Computer Science

The term "Real-Time Operating System (RTOS)" refers to systems wherein the time component is critical. For example, one or more of a computer's peripheral devices send a signal, and the computer must respond appropriately within a specified period of time. Examples include: the monitoring system in a hospital care unit, the autopilot in the aircraft, and the safety control system in the nuclear reactor. Scheduling is a method that ensures that jobs are performed at certain times. In the real-time systems, accuracy does not only rely on the outcomes of calculation, and also on the time it takes to provide the results. It must be completed within the specified time frame. The scheduling strategy is crucial in any real-time system, which is required to prevent overlapping execution in the system. The paper review classifies several previews works on many characteristics. Also, strategies utilized for scheduling in real time are examined and their features compared.

2009 10th International Symposium on Pervasive Systems, Algorithms, and Networks, 2009

Nowadays, most embedded systems support different kinds of multimedia applications and real-time tasks. The computational requirements of multimedia applications are usually very expensive and embedded systems may not be powerful enough to support multiple multimedia applications. As a result, real-time tasks will miss their deadlines and thus get rejected. To solve this problem, we propose a Dynamic Workload Shaping (DWS) method by extending a Dynamic Buffering Technique to multiple multimedia tasks and integrating two optimization methods. The scheduling method dynamically changes the playout buffer fill level of multimedia applications to periodically free up sufficient processor bandwidth to support other concurrently running real-time applications. The original scheduling method can only guarantee that the playout devices can always read out data items from the playout buffers, but cannot guarantee any QoS. Two algorithms are proposed in this work to optimize and guarantee the quality of multimedia applications. The first algorithm optimizes the multimedia playout device rates, in terms of frames per second, while allowing a real-time task to meet its deadline. The second algorithm optimizes the processor bandwidth allocations, in terms of MHz, given to each of the multimedia tasks, while allowing a real-time task to meet its deadline. We use several examples to illustrate how both algorithms can be applied to real systems.

2006

In order to enhance performance and improve predictability of the real time systems, implementing some critical operating system functionalities, like time management and task scheduling, in software and others in hardware is an interesting approach. Scheduling decision for real-time embedded software applications is an important problem in real-time operating system (RTOS) and has a great impact on system performance. In this paper, we evaluate the pros and cons of migrating RTOS scheduler implementation from software to hardware. We investigate three different RTOS scheduler implementation approaches: (i) implemented in software running in the same processor of the application tasks, (ii) implemented in software running in a co-processor, and (iii) implemented in hardware, while application tasks are running on a processor. We demonstrate the effectiveness of each approach by simulating and analyzing a set of benchmarks representing different embedded application classes.

2005

Integration of middleware scheduling and resource management services enables open distributed real-time embedded (DRE) applications to meet end-to-end quality of service (QoS) requirements in highly variable operating environments. This paper describes our research 1 on integrating CORBA scheduling and resource management services, and presents experiments we conducted to validate and quantify the benefits of this integration.

Lecture Notes in Computer Science, 2005

Real-time scheduling is the kernel mechanism having the most impact on RTOS performance. After describing existing algorithms and methodologies for embedded realtime applications, we present their limitations in handling dynamic environments, and discuss new research trends for overcoming them in next generation operating systems. 20.1 Landscape This summary is intended to give a brief overview of the status of scheduling methods, in particular with respect to flexible scheduling. It does not aim to be complete or provide in-depth literature survey. Rather, directions and issues, together with seminal algorithms are presented. Most of the presented algorithms are research prototypes.

ARTOSS

Resource Reservation (RR) is a class of real-time schedulers, proposed by the research community for hard and soft real-time systems, which are receiving considerable attention from industry. With this white paper, we would like to trigger a broad discussion between the academic and the industrial world on the use of RR techniques in standard operating systems. After presenting the major reasons for using RR ("why"), we present a set of propositions on "what" and "how" should be provided, which pinpoint the demands on operating systems and the research issues that remain to be addressed.

Avishi, 2024

Efficiency within real-time and embedded systems heavily relies on scheduling algorithms crafted to meet the demanding requirements of various applications. This paper delves into diverse scheduling strategies aimed at optimizing energy consumption while adhering to timing constraints in heterogeneous distributed systems. Initially, we explore the incorporation of the latest finish time (LFT) concept with dynamic voltage and frequency scaling (DVFS) to minimize energy consumption yet identify limitations due to restricted frequency scaling. To address this, we propose a novel approach that combines non-DVFS energy-efficient scheduling (NDES) and global DVFSenabled energy-efficient scheduling (GDES) algorithms. NDES utilizes deadline slacks to reduce energy consumption while upholding deadlines, whereas GDES optimizes energy consumption across different processors. Experimental results demonstrate significant energy savings of up to 36.25-55.65% compared to existing methods. Additionally, we delve into static and dynamic variable voltage scheduling for multi-rate periodic task graphs, ensuring hard deadlines and precedence relationships in heterogeneous distributed real-time embedded systems. Furthermore, we introduce a controlled preemptive EDF (CP-EDF) scheduling algorithm to mitigate processor time and energy wastage, outperforming existing algorithms in terms of success ratio, missing rate, and CPU utilization. Our study underscores the critical role of scheduling algorithms in enhancing the performance and efficiency of real-time and embedded systems, providing insights into specialized approaches tailored to specific application requirements.

Microprocessors and Microsystems

Task scheduling in heterogeneous environments such as cloud data centers is considered to be an NPcomplete problem. Efficient task scheduling will lead to balance the load on the virtual machines (VMs) thereby achieving effective resource utilization. Hence there is a need for a new scheduling framework to perform load balancing amid considering multiple quality of service (QoS) metrics such as makespan, response time, execution time, and task priority. Multi-core Web server is difficult to achieve dynamic balance in the process of remote dynamic request scheduling, so it is necessary to improve it based on the traditional scheduling algorithm to enhance the actual effect of the algorithm. This article do research on the multi-core Web server, Focusing on multi-core Web server queuing model. On this basis, the author draws the drawbacks of the multi-core Web server in the remote dynamic request scheduling algorithm, and improves the traditional algorithm with the demand analysis. Not only it overcomes the drawbacks of traditional algorithms, but also promotes the system threads carrying the same amount of tasks, and promotes the server being always in a dynamic balance. On the basis of this, it achieves an effective solution to customer requests.

2008

Abstract Effective resource management for distributed real-time embedded (DRE) systems is hard due to their unique characteristics, including (1) constraints in multiple resources and (2) highly fluctuating resource availability and input workload. DRE systems can benefit from a middleware framework that enables adaptive resource management algorithms to ensure application QoS requirements are met. This paper identifies key challenges in designing and extending resource allocation algorithms for DRE systems.