Hybrid Multiprocessor Real-Time Scheduling Approach

MATEC Web of Conferences, 2019

Generally, multiprocessor real-time scheduling algorithm fall into two basic approaches, partitioned and global. The hybrid solution that we proposed applies the partitioned scheduling approach to the task set until all processors have been filled. The remaining tasks are then scheduled using the global scheduling approach. The idea of a hybrid scheduling approach to ameliorate limitations of partitioned and global approaches. Studies have shown that most prior research on hybrid multiprocessor real-time scheduling has been confined to hard and soft real-time tasks. In fact, the implementation of hybrid approach and the performance of such algorithms in comparison to partitioned and global approaches have not been fully answered by previous studies. This paper performs experimental evaluation of our proposed hybrid multiprocessor scheduling approach, R-BOUND-MP-NFRNS and RM-US (m/3m-2) with multiprocessor response time test, with one of the best scheduling approach from partitioned ...

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.

Journal of Software, 2010

This paper proposes a hybrid scheduling approach for real-time system on homogeneous multi-core architecture. To make the best of the available parallelism in these systems, first an application is partitioned into some parallel tasks as much as possible. Then the parallel tasks are dispatched to different cores, so as to execute in parallel. In each core, real-time tasks can run concurrently with nonreal-time tasks. The hybrid scheduling approach uses a twolevel scheduling scheme. At the top level, a sporadic server is assigned to each scheduling policy. Each sporadic server is used to schedule the dispatched tasks according to its scheduling policy. At the bottom level, a rate-monotonic OS scheduler is adopted to maintain and schedule the top level sporadic servers. The schedulability test is also considered in this paper. The experimental results show that the hybrid scheme is an efficient scheduling scheme.

Computing Research Repository, 2011

An optimal solution to the problem of scheduling real-time tasks on a set of identical processors is derived. The described approach is based on solving an equivalent uniprocessor real-time scheduling problem. Although there are other scheduling algorithms that achieve optimality, they usually impose prohibitive preemption costs. Unlike these algorithms, it is observed through simulation that the proposed approach produces no more than three preemptions points per job.

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.

Control Engineering Practice, 1997

This paper analyzes the behavior and performance of four dynamic algorithms for multiprocessor scheduling of hard real-time tasks. The well known algorithms are the Earliest Deadline First (EDF) algorithm and the Least Laxity First (LLF) algorithm. An important feature of the original ones is that they are guarantee-oriented. The performance of these algorithms has been measured through simulations which analyze the behavior of the algorithms under two main load hypothesis: static load and dynamic load. Simulation results present practical bounds and a comparative study on the loads that they are able to guarantee, context switches and cpu utilization.

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.

Imprecise computation model is used in dynamic scheduling algorithm having heuristic function to schedule task sets. A task is characterized by ready time, worst case computation time, deadline and resource requirements. A task failing to meet its deadline and resource requirements on time is split into mandatory part and optional part. These sub-tasks of a task can execute concurrently on multiple cores, thus achieving parallelization provided by the multi-core system. Mandatory part produces acceptable results while optional part refines the result further. To study the effectiveness of proposed scheduling algorithm, extensive simulation studies have been carried out. Performance of proposed scheduling algorithm is compared with myopic and improved myopic scheduling algorithm. The simulation studies shows that schedulability of task split myopic algorithm is always higher than myopic and improved myopic algorithm.

International Journal of Computer Applications, 2015

In this paper, main scheduling algorithms for hard real-time systems (RTSs) have been investigated that include both uni and multi processors schemes. It provides the summary of schedulability analysis and well-known attributes. This paper composed of two parts; first part surveyed the basic hard RTS scheduling algorithms that guarantee the on-time completion of the tasks. Second part contains the different heuristic and partitioned approaches for some specific factors of real-time systems such as energy consumption, dependability, performance, scheduling feasibility and utilization of memory resource. Finally, the analysis and evaluation of the mentioned methods are shown based on the schedulability of task sets and efficiency.

Real-Time systems are becoming pervasive. In a Real-Time System the correctness of the system behavior depends not only on the logical results of the computations, but also on the physical instant at which these results are produced. A missed deadline in hard real-time systems is catastrophic and in soft real-time systems it can lead to a significant loss .This work talks about static and dynamic scheduling algorithms for real time task. The problem of real-time scheduling spans a broad spectrum of algorithms from simple uniprocessor to highly sophisticated multiprocessor scheduling algorithms which are priority driven and divided into three classes fixed priority, dynamic priority and hybrid priority. Finally conclusion shows that Instantaneous utilization factor scheduling Algorithm gives better result in uniprocessor scheduling algorithms and Modified Instantaneous utilization factor scheduling Algorithm gives better context switching, response time and CPU utilization as compared to previous scheduling algorithms.