Download or read book Toward Efficient Scheduling for Parallel Real time Tasks on Multiprocessors written by Son Ngoc Dinh and published by . This book was released on 2020 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modern real-time applications are becoming more demanding computationally while their temporal requirements, dictated by the physical world, often remain unchanged. This coupled with the increasing prevalence of multiprocessors in real-time systems necessitates that highly computation-demanding real-time tasks need to be parallelized to exploit the parallelism offered by the underlying hardware, in order to satisfy their temporal constraints. Scheduling parallel real-time tasks, however, introduces a new layer of complexity due to the allowance for intra-task parallelism. This dissertation addresses the problem of scheduling parallel real-time tasks in which tasks may (or may not) access shared non-processor resources, such as in-memory buffers or data structures. Specifically, for independent tasks, we propose new scheduling algorithms and schedulability analyses for parallel tasks with these characteristics, under federated and global scheduling.Experimental results show that the proposed algorithms and analyses improve the previously introduced methods. For parallel tasks that may access shared non-processor resources, we present a blocking analysis for two different types of spinlocks; through evaluations, we make a recommendation for a preferable ordering of locks. We also study practical runtime parallel scheduler designs for soft real-time applications and present a design that is more suitable for soft real-time systems.

Download or read book Partitioning and Scheduling Parallel Programs for Multiprocessors written by Vivek Sarkar and published by Pitman Publishing. This book was released on 1989 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is one of the first to address the problem of forming useful parallelism from potential parallelism and to provide a general solution. The book presents two approaches to automatic partitioning and scheduling so that the same parallel program can be made to execute efficiently on widely different multiprocessors. The first approach is based on a macro dataflow model in which the program is partitioned into tasks at compile time and the tasks are scheduled on processors at run time. The second approach is based on a compile time scheduling model, where both the partitioning and scheduling are performed at compile time. Both approaches have been implemented in partition programs written in the single assignment language SISAL. The inputs to the partitioning and scheduling algorithms are a graphical representation of the parallel program and a list of parameters describing the target multiprocessor. Execution profile information is used to derive compile-time estimates of execution times and data sizes in the program. Both the macro dataflow and compile-time scheduling problems are expressed as optimization problems and are shown to be NP complete in the strong sense. Efficient approximation algorithms for these problems are presented. Finally, the effectiveness of the partitioning and scheduling algorithms is studied by multiprocessor simulations of various SISAL benchmark programs for different target multiprocessor parameters. Vivek Sarkar is a Member of Research Staff at the IBM T. J. Watson Research Center. Partitioning and Scheduling Parallel Programs for Multiprocessing is included in the series Research Monographs in Parallel and Distributed Computing. Copublished with Pitman Publishing.

Download or read book Energy Efficient Scheduling of Parallel Real time Tasks on Heterogeneous Multicore Systems written by Houssam-Eddine Zahaf and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cyber physical systems (CPS) and Internet of Objects (IoT) are generating an unprecedented volume and variety of data that needs to be collected and stored on the cloud before being processed. By the time the data makes its way to the cloud for analysis, the opportunity to trigger a reply might be late. One approach to solve this problem is to analyze the most time-sensitive data at the network edge, close to where it is generated. Thus, only the pre-processed results are sent to the cloud. This computation model is know as *Fog Computing* or *Edge computing*. Critical CPS applications using the fog computing model may have real-time constraints because results must be delivered in a pre-determined time window. Furthermore, in many relevant applications of CPS, the processing can be parallelized by applying the same processing on different sub-sets of data at the same time by the mean parallel programming techniques. This allow to achieve a shorter response time, and then, a larger slack time, which can be used to reduce energy consumption. In this thesis we focus on the problem of scheduling a set of parallel tasks on multicore processors, with the goal of reducing the energy consumption while all deadlines are met. We propose several realistic task models on architectures with identical and heterogeneous cores, and we develop algorithms for allocating threads to processors, select the core frequencies, and perform schedulability analysis. The proposed task models can be realized by using OpenMP-like APIs.

Download or read book Energy aware Scheduling on Multiprocessor Platforms written by Dawei Li and published by Springer Science & Business Media. This book was released on 2012-10-20 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multiprocessor platforms play important roles in modern computing systems, and appear in various applications, ranging from energy-limited hand-held devices to large data centers. As the performance requirements increase, energy-consumption in these systems also increases significantly. Dynamic Voltage and Frequency Scaling (DVFS), which allows processors to dynamically adjust the supply voltage and the clock frequency to operate on different power/energy levels, is considered an effective way to achieve the goal of energy-saving. This book surveys existing works that have been on energy-aware task scheduling on DVFS multiprocessor platforms. Energy-aware scheduling problems are intrinsically optimization problems, the formulations of which greatly depend on the platform and task models under consideration. Thus, Energy-aware Scheduling on Multiprocessor Platforms covers current research on this topic and classifies existing works according to two key standards, namely, homogeneity/heterogeneity of multiprocessor platforms and the task types considered. Under this classification, other sub-issues are also included, such as, slack reclamation, fixed/dynamic priority scheduling, partition-based/global scheduling, and application-specific power consumption, etc.

Download or read book Memory Efficient Scheduling for Multicore Real time Systems written by Ahmed Alhammad and published by . This book was released on 2016 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modern real-time systems are becoming increasingly complex and requiring significant computational power to meet their demands. Since the increase in uniprocessor speed has slowed down in the last decade, multicore processors are now the preferred way to supply the increased performance demand of real-time systems. A significant amount of work in the real-time community has focused on scheduling solutions for multicore processors for both sequential and parallel real-time tasks. Even though such solutions are able to provide strict timing guarantees on the overall response time of real-time tasks, they rely on the assumption that the worst-case execution time (WCET) of each individual task is known. However, physical shared resources such as main memory and I/O are heavily employed in multicore processors. These resources are limited and therefore subject to contention. In fact, the execution time of one task when run in parallel with other tasks is significantly larger than the execution time of the same task when run in isolation. In addition, the presence of shared resources increases the timing unpredictability due to the conflicts generated by multiple cores. As a result, the adoption of multicore processors for real-time systems is dependent upon solving such sources of unpredictability. In this dissertation, we investigate memory bus contention. In particular, two main problems are associated with memory contention: (1) unpredictable behavior and (2) hindrance of performance. We show how to mitigate these two problems through scheduling. Scheduling is an attractive tool that can be easily integrated into the system without the need for hardware modifications. We adopt an execution model that exposes memory as a resource to the scheduling algorithm. Thus, the theory of real-time multiprocessor scheduling, that has seen significant advances in recent years, can be utilized to schedule both processor cores and memory. Since the real-time workload on multicore processors can be modeled as sequential or parallel tasks, we also study parallel task scheduling by taking memory time into account.

Download or read book Multiprocessor Scheduling for Real Time Systems written by Sanjoy Baruah and published by Springer. This book was released on 2015-01-02 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive overview of both theoretical and pragmatic aspects of resource-allocation and scheduling in multiprocessor and multicore hard-real-time systems. The authors derive new, abstract models of real-time tasks that capture accurately the salient features of real application systems that are to be implemented on multiprocessor platforms, and identify rules for mapping application systems onto the most appropriate models. New run-time multiprocessor scheduling algorithms are presented, which are demonstrably better than those currently used, both in terms of run-time efficiency and tractability of off-line analysis. Readers will benefit from a new design and analysis framework for multiprocessor real-time systems, which will translate into a significantly enhanced ability to provide formally verified, safety-critical real-time systems at a significantly lower cost.

Download or read book Efficient Scheduling of Parallel Tasks in a Multiprogramming Environment written by Dale Allen Schouten and published by . This book was released on 1995 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: "Considerable research has produced a plethora of efficient methods of exploiting parallelism on dedicated machines. On typical real systems, however, some of the important assumptions that lead to efficiency on a dedicated machine either do not hold or cause other problems on a machine which is time or space shared. Foremost among these assumptions is that the number of processors available to a parallel job is constant throughout the execution of the job. Maintaining such consistency in a real multiprogramming system can lead to poor utilization of the machine. This thesis will address issues involving the efficient exploitation of parallelism in a multiprogramming environment including OS support for user level scheduling and dynamic granularity control. Implementation of some of these techniques in the nanoThreads thread library will be discussed, as well as other details of the implementation of nanoThreads."

Download or read book Task Scheduling for Parallel Systems written by Oliver Sinnen and published by John Wiley & Sons. This book was released on 2007-05-04 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new model for task scheduling that dramatically improves the efficiency of parallel systems Task scheduling for parallel systems can become a quagmire of heuristics, models, and methods that have been developed over the past decades. The author of this innovative text cuts through the confusion and complexity by presenting a consistent and comprehensive theoretical framework along with realistic parallel system models. These new models, based on an investigation of the concepts and principles underlying task scheduling, take into account heterogeneity, contention for communication resources, and the involvement of the processor in communications. For readers who may be new to task scheduling, the first chapters are essential. They serve as an excellent introduction to programming parallel systems, and they place task scheduling within the context of the program parallelization process. The author then reviews the basics of graph theory, discussing the major graph models used to represent parallel programs. Next, the author introduces his task scheduling framework. He carefully explains the theoretical background of this framework and provides several examples to enable readers to fully understand how it greatly simplifies and, at the same time, enhances the ability to schedule. The second half of the text examines both basic and advanced scheduling techniques, offering readers a thorough understanding of the principles underlying scheduling algorithms. The final two chapters address communication contention in scheduling and processor involvement in communications. Each chapter features exercises that help readers put their new skills into practice. An extensive bibliography leads to additional information for further research. Finally, the use of figures and examples helps readers better visualize and understand complex concepts and processes. Researchers and students in distributed and parallel computer systems will find that this text dramatically improves their ability to schedule tasks accurately and efficiently.

Download or read book Resource efficient Scheduling of Multiprocessor Mixed criticality Real time Systems written by Jaewoo Lee and published by . This book was released on 2017 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: Timing guarantee is critical to ensure the correctness of embedded software systems that interact with the physical environment. As modern embedded real-time systems evolves, they face three challenges: resource constraints, mixed-criticality, and multiprocessors. This dissertation focuses on resource-efficient scheduling techniques for mixed-criticality systems on multiprocessor platforms.While Mixed-Criticality (MC) scheduling has been extensively studied on uniprocessor platforms, the problem on multiprocessor platforms has been largely open. Multiprocessor algorithms are broadly classified into two categories: global and partitioned. Global scheduling approaches use a global run-queue and migrate tasks among processors for improved schedulability. Partitioned scheduling approaches use per processor run-queues and can reduce preemption/migration overheads in real implementation. Existing global scheduling schemes for MC systems have suffered from low schedulability. Our goal in the first work is to improve the schedulability of MC scheduling algorithms. Inspired by the fluid scheduling model in a regular (non-MC) domain, we have developed the MC-Fluid scheduling algorithm that executes a task with criticality-dependent rates. We have evaluated MC-Fluid in terms of the processor speedup factor: MC-Fluid is a multiprocessor MC scheduling algorithm with a speed factor of 4/3, which is known to be optimal. In other words, MC-Fluid can schedule any feasible mixed-criticality task system if each processor is sped up by a factor of 4/3. Although MC-Fluid is speedup-optimal, it is not directly implementable on multiprocessor platforms of real processors due to the fractional processor assumption where multiple task can be executed on one processor at the same time. In the second work, we have considered the characteristic of a real processor (executing only one task at a time) and have developed the MC-Discrete scheduling algorithm for regular (non-fluid) scheduling platforms. We have shown that MC-Discrete is also speedup-optimal. While our previous two works consider global scheduling approaches, our last work considers partitioned scheduling approaches, which are widely used in practice because of low implementation overheads. In addition to partitioned scheduling, the work considers the limitation of conventional MC scheduling algorithms that drops all low-criticality tasks when violating a certain threshold of actual execution times. In practice, the system designer wants to execute the tasks as much as possible. To address the issue, we have developed the MC-ADAPT scheduling framework under uniprocessor platforms to drop as few low-criticality tasks as possible. Extending the framework with partitioned multiprocessor platforms, we further reduce the dropping of low-criticality tasks by allowing migration of low-criticality tasks at the moment of a criticality switch. We have evaluated the quality of task dropping solution in terms of speedup factor. In existing work, the speedup factor has been used to evaluate MC scheduling algorithms in terms of schedulability under the worst-case scheduling scenario. In this work, we apply the speedup factor to evaluate MC scheduling algorithms in terms of the quality of their task dropping solution under various MC scheduling scenarios. We have derived that MC-ADAPT has a speedup factor of 1.618 for task dropping solution.

Download or read book Scheduling for Parallel Processing written by Maciej Drozdowski and published by Springer Science & Business Media. This book was released on 2010-03-14 with total page 395 pages. Available in PDF, EPUB and Kindle. Book excerpt: Overview and Goals This book is dedicated to scheduling for parallel processing. Presenting a research ?eld as broad as this one poses considerable dif?culties. Scheduling for parallel computing is an interdisciplinary subject joining many ?elds of science and te- nology. Thus, to understand the scheduling problems and the methods of solving them it is necessary to know the limitations in related areas. Another dif?culty is that the subject of scheduling parallel computations is immense. Even simple search in bibliographical databases reveals thousands of publications on this topic. The - versity in understanding scheduling problems is so great that it seems impossible to juxtapose them in one scheduling taxonomy. Therefore, most of the papers on scheduling for parallel processing refer to one scheduling problem resulting from one way of perceiving the reality. Only a few publications attempt to arrange this ?eld of knowledge systematically. In this book we will follow two guidelines. One guideline is a distinction - tween scheduling models which comprise a set of scheduling problems solved by dedicated algorithms. Thus, the aim of this book is to present scheduling models for parallel processing, problems de?ned on the grounds of certain scheduling models, and algorithms solving the scheduling problems. Most of the scheduling problems are combinatorial in nature. Therefore, the second guideline is the methodology of computational complexity theory. Inthisbookwepresentfourexamplesofschedulingmodels. Wewillgodeepinto the models, problems, and algorithms so that after acquiring some understanding of them we will attempt to draw conclusions on their mutual relationships.

Download or read book Real time Scheduling Algorithms for Precedence Related Tasks on Heterogeneous Multiprocessors written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The problem of real-time scheduling has been very well researched for the single processor case and the identical multiprocessor case. There are a number of efficient algorithms and schedulability tests that enable the system designer to model his/her application as a set of real-time tasks. However, it may very well be the case that the multiprocessor system consists of processors with different speeds and configurations. This heterogeneity makes the scheduling problem much more complex. Real-time scheduling on heterogeneous multiprocessors has not received much attention in the scheduling literature. We propose several algorithms for scheduling a set of precedence related tasks on heterogeneous multiprocessors. In the first section, we propose a reliability driven algorithm for scheduling periodic tasks on heterogeneous systems. We relax the assumption that all the processors in the system are equally reliable. We introduce a new metric called cost of dependability. The periodic tasks are assigned to processors in such a way that the reliability of the system is maximized. We observe that our scheme generate schedules that are consistently more reliable than the schedules generated by algorithms that do not take the reliability of the processors into account. In the second section, we propose a duplication based algorithm for scheduling a set of soft deadline tasks on a system of heterogeneous multiprocessors. We observe that communicating tasks assigned to different processors have to incur a delay by using the inter-processor communication channel. By duplicating any of these two tasks on either assigned processor, we can cut down on that delay. Hence tasks can start (and hence finish) earlier. This leads to a larger number of tasks meeting their deadlines and hence an increase in the guarantee ratio of the real-time application. The next section extends the concept of task duplication to a set of hard deadline tasks. The deadlines are hard in that even a single deadline miss could lead to catastrophic results. By employing task duplication, we observe that a larger number of task sets are able to finish execution before their deadlines. Hence, the success ratio of the application experiences an increment. Based on our simulation results, we observe that our proposed algorithm offers a higher success ratio as compared to the other algorithms that do not use task duplication. It may very well be the case that the real-time application consists of a mix of tasks with hard and soft deadlines. In the next section, we propose an integrated scheme for scheduling a mix of hard and soft deadline tasks on heterogeneous multiprocessors. We observe that our scheme offers a better schedulability as compared to the other algorithms in the literature when sufficient processors are available and when communication is a dominant factor in the system. Moreover, our algorithm is scalable in that the application can be scheduled even if sufficient processors are not available for the initial cluster generation.

Download or read book Scheduling Sequential Or Parallel Hard Real time Pre emptive Tasks Upon Identical Multiprocessor Platforms written by Pierre Courbin and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The scheduling of tasks on a hard real-time system consists in finding a way to choose, at each time instant, which task should be executed on the processor so that each succeed to complete its work before its deadline. In the uniprocessor case, this problem is already well studied and enables us to do practical applications on real systems (aerospace, stock exchange etc.). Today, multiprocessor platforms are widespread and led to many issues such as the effective use of all processors. In this thesis, we explore the existing approaches to solve this problem. We first study the partitioning approach that reduces this problem to several uniprocessor systems and leverage existing research. For this one, we propose a generic partitioning algorithm whose parameters can be adapted according to different goals. We then study the semi-partitioning approach that allows migrations for a limited number of tasks. We propose a solution with restricted migration that could be implemented rather simply on real systems. We then propose a solution with unrestricted migration which provides better results but is more difficult to implement. Finally, programmers use more and more the concept of parallel tasks that can use multiple processors simultaneously. These tasks are still little studied and we propose a new model to represent them. We study the possible schedulers and define a way to ensure the schedulability of such tasks for two of them.

Download or read book Parallel Real time Scheduling for Latency critical Applications written by Jing Li (Computer scientist) and published by . This book was released on 2017 with total page 337 pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to provide safety guarantees or quality of service guarantees, many of today's systems consist of latency-critical applications, e.g. applications with timing constraints. The problem of scheduling multiple latency-critical jobs on a multiprocessor or multicore machine has been extensively studied for sequential (non-parallizable) jobs and different system models and different objectives have been considered. However, the computational requirement of a single job is still limited by the capacity of a single core. To provide increasingly complex functionalities of applications and to complete their higher computational demands within the same or even more stringent timing constraints, we must exploit the internal parallelism of jobs, where individual jobs are parallel programs and can potentially utilize more than one core in parallel. However, there is little work considering scheduling multiple parallel jobs that are latency-critical. This dissertation focuses on developing new scheduling strategies, analysis tools, and practical platform design techniques to enable efficient and scalable parallel real-time scheduling for latency-critical applications on multicore systems. In particular, the research is focused on two types of systems: (1) static real-time systems for tasks with deadlines where the temporal properties of the tasks that need to execute is known a priori and the goal is to guarantee the temporal correctness of the tasks prior to their executions; and (2) online systems for latency-critical jobs where multiple jobs arrive over time and the goal to optimize for a performance objective of jobs during the execution. For static real-time systems for parallel tasks, several scheduling strategies, including global earliest deadline first, global rate monotonic and a novel federated scheduling, are proposed, analyzed and implemented. These scheduling strategies have the best known theoretical performance for parallel real-time tasks under any global strategy, any fixed priority scheduling and any scheduling strategy, respectively. In addition, federated scheduling is generalized to systems with multiple criticality levels and systems with stochastic tasks. Both numerical and empirical experiments show that federated scheduling and its variations have good schedulability performance and are efficient in practice. For online systems with multiple latency-critical jobs, different online scheduling strategies are proposed and analyzed for different objectives, including maximizing the number of jobs meeting a target latency, maximizing the profit of jobs, minimizing the maximum latency and minimizing the average latency. For example, a simple First-In-First-Out scheduler is proven to be scalable for minimizing the maximum latency. Based on this theoretical intuition, a more practical work-stealing scheduler is developed, analyzed and implemented. Empirical evaluations indicate that, on both real world and synthetic workloads, this work-stealing implementation performs almost as well as an optimal scheduler.

Download or read book Scheduling Parallel Real time Tasks that Allow Imprecise Results written by Albert Chuang-Shi Yu and published by . This book was released on 1992 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Embedded Multiprocessors written by Sundararajan Sriram and published by CRC Press. This book was released on 2018-10-03 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt: Techniques for Optimizing Multiprocessor Implementations of Signal Processing Applications An indispensable component of the information age, signal processing is embedded in a variety of consumer devices, including cell phones and digital television, as well as in communication infrastructure, such as media servers and cellular base stations. Multiple programmable processors, along with custom hardware running in parallel, are needed to achieve the computation throughput required of such applications. Reviews important research in key areas related to the multiprocessor implementation of multimedia systems Embedded Multiprocessors: Scheduling and Synchronization, Second Edition presents architectures and design methodologies for parallel systems in embedded digital signal processing (DSP) applications. It discusses application modeling techniques for multimedia systems, the incorporation of interprocessor communication costs into multiprocessor scheduling decisions, and a modeling methodology (the synchronization graph) for multiprocessor system performance analysis. The book also applies the synchronization graph model to develop hardware and software optimizations that can significantly reduce the interprocessor communication overhead of a given schedule. Chronicles recent activity dealing with single-chip multiprocessors and dataflow models This edition updates the background material on existing embedded multiprocessors, including single-chip multiprocessors. It also summarizes the new research on dataflow models for signal processing that has been carried out since the publication of the first edition. Harness the power of multiprocessors This book explores the optimization of interprocessor communication and synchronization in embedded multiprocessor systems. It shows you how to design multiprocessor computer systems that are streamlined for multimedia applications.

Download or read book Proceedings of the 4th International Conference on Frontiers in Intelligent Computing Theory and Applications FICTA 2015 written by Swagatam Das and published by Springer. This book was released on 2015-10-24 with total page 703 pages. Available in PDF, EPUB and Kindle. Book excerpt: The proceedings of the 4th International Conference on Frontiers in Intelligent Computing: Theory and Applications 2015 (FICTA 2015) serves as the knowledge centre not only for scientists and researchers in the field of intelligent computing but also for students of post-graduate level in various engineering disciplines. The book covers a comprehensive overview of the theory, methods, applications and tools of Intelligent Computing. Researchers are now working in interdisciplinary areas and the proceedings of FICTA 2015 plays a major role to accumulate those significant works in one arena. The chapters included in the proceedings inculcates both theoretical as well as practical aspects of different areas like Nature Inspired Algorithms, Fuzzy Systems, Data Mining, Signal Processing, Image processing, Text Processing, Wireless Sensor Networks, Network Security and Cellular Automata.

Download or read book Efficient Scheduling of Parallel Tasks in a Multiprogramming Environment written by University of Illinois at Urbana-Champaign. Department of Computer Science and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: