Survey of Real Time Scheduling Algorithms

ijcsit.com

This paper proposes a new novel scheduling algorithms to schedule periodic tasks for soft real time system. This is a planning based offline scheduler where tasks are scheduled on the basis of its instantaneous utilization. Here after every quantum of execution, instantaneous utilization of each task is calculated. Task which is having highest instantaneous utilization is scheduled to the processor. Since Instantaneous utilization factor(IUF) is temporarily variant factor, the priority of each task will vary continuously. Also It is often more desirable to complete some portions of every task rather than giving up completely the processing of some tasks. The Imprecise Computation Model was introduced to allow for the tradeoff of the quality of computations in favor of meeting the deadline constraints. It is observed that scheduling performance metrics such as schedulability, CPU utilization, context switching, response time and reliability are improved by this approach as compared to scheduling algorithms such as RM, EDF, LLF, MUF scheduling algorithms.

Scheduling is a technique which makes an arrangement of performing certain tasks at specified period. The intervals between each function have been clearly defined by the algorithm to avoid any overlapping. The real time computing systems are those in which there are strict timing constraints that have to be met to get the correct output i.e. the output not only depend on the correctness of the outcome but also on the time at which results are produced. Real time systems are expected to change its state in real time even after the controlling processor has stopped its execution. The bound in which real time applications are needed to respond to the stimuli is known as deadline. In order to achieve optimized results in a real rime operations the scheduling techniques has been used. In the paper we classify the various scheduling techniques based on different parameters. Also techniques used for scheduling in real time environment are analyzed and comparison between different techniques have been done. The various issues have been presented on which there is still a need to work.

IJRCAR, 2014

Real time systems have been an active topic of research since the late 1960. The most important factor in real time scheduling is Time. Real time system supports the applications that meet their deadlines. In real time system the correctness of the system depends on their temporal aspects as well as their functional aspects. A missed deadline can create a catastrophic fault in the system when talking about a hard real time system whereas in soft real time system it can lead to certain loss .Thus there are different scheduling algorithms to deal to above said, classified as Static & Dynamic Scheduling Algorithms. Thus, In this paper an Overview of different scheduling algorithm of a uniprocessor system are illustrated.

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.

IJRCAR, 2014

The problem of real-time scheduling spans a broad spectrum of algorithms from simple uniprocessor to highly sophisticated multiprocessor scheduling algorithms. Real-time software must satisfy not only functional correctness requirements but also timeliness requirements. A lot of real-time researches were focused on analysis rather than testing recently, observes that real-time testing is still a “lost-world” compared to “civilization” developed in other areas of software, reflecting the little work done in the area. In this paper, we have studied the various scheduling algorithm of the real time system.

Scheduling of real time tasks are very important aspect in systems as processes should complete its task at a specific time. There is a need of high energy efficiency and low response time in large data stream so for this energy efficient resources and optimized frameworks are needed. Both hard real time and mixed critically systems are targeted. Soft deadline can be handled while hard deadlines are difficult to cater. Different algorithms are used to schedule tasks like rate monotonic, earliest deadline first, deadline monotonic etc.

2009 Second International Conference on Emerging Trends in Engineering & Technology, 2009

The problem of real time scheduling spans a broad spectrum of algorithms from simple uniprocessor to highly sophisticated multiprocessor scheduling algorithm. This paper proposes a new novel scheduling algorithm to scheduler periodic task for soft real time systems .This is a planning based scheduler where tasks are scheduled on the basis of its instantaneous utilization .Here after every quantum of execution, instantaneous utilization of each task is calculated. task which is having highest instantaneous utilization is scheduled to the processor. Since Instantaneous Utilization Factor (IUF) is temporarily variant factor, the priority of each task will vary continuously. Experimentally IUF based scheduling shows better performance result like missing of deadline, predictability, schedulability and sustainability as compared to scheduling algorithm such as EDF, RM, LLF.

Most currently existing optimal real-time multiprocessor scheduling algorithms follow the fairness rule, in which all tasks are forced to make progress in their executions proportional to their utilization, to ensure the optimality of the algorithm. However, obeying the fairness rule results in large number of task preemptions and migrations and these highly affect the practicability of the algorithm. In this paper, we present an efficient real-time multiprocessor scheduling algorithm in which the fairness rule is completely relaxed and a semi-greedy algorithm is introduced. In the simulation, the proposed algorithm showed promising results in terms of number of task preemptions and migrations that are very few compared to the current state of the art real-time multiprocessor scheduling algorithms. Although the algorithm can sometimes miss a very few deadlines, we assume that these deadline misses can be tolerated in view of the great reduction of task preemptions and migrations.

IEEE Transactions on Parallel and Distributed Systems, 1998

Many time-critical applications require predictable performance and tasks in these applications have deadlines to be met. In this paper, we propose an efficient algorithm for nonpreemptive scheduling of dynamically arriving real-time tasks (aperiodic tasks) in multiprocessor systems. A real-time task is characterized by its deadline, resource requirements, and worst case computation time on p processors, where p is the degree of parallelization of the task. We use this parallelism in tasks to meet their deadlines and, thus, obtain better schedulability compared to nonparallelizable task scheduling algorithms. To study the effectiveness of the proposed scheduling algorithm, we have conducted extensive simulation studies and compared its performance with the myopic [8] scheduling algorithm. The simulation studies show that the schedulability of the proposed algorithm is always higher than that of the myopic algorithm for a wide variety of task parameters.

2013

Abstract- The main objective of this paper is to develop a new approach for round robin C P U scheduling a l g o r i t h m which improves the performance of CPU in real time operating system. The proposed Priority based Round-Robin CPU Scheduling algorithm is based on the integration of round-robin and priority scheduling algorithm. It retains the advantage of round robin in reducing starvation and also integrates the advantage of priority scheduling. The proposed algorithm also implements the concept of aging by assigning new priorities to the processes. Existing round robin CPU scheduling algorithm cannot be implemented in real time operating system due to their high context switch rates, large waiting time, large response time, large turnaround time and less throughput. The proposed algorithm improves all the drawbacks of round robin C P U scheduling algorithm. The paper also presents the comparative analysis of proposed algorithm with existing round robin scheduling algorithm on...