Download or read book Efficient Scheduling Algorithms for Real time Multiprocessor Systems written by University of Massachusetts at Amherst. Department of Computer and Information Science and published by . This book was released on 1989 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 Architecture and Design of Distributed Embedded Systems written by Bernd Kleinjohann and published by Springer Science & Business Media. This book was released on 2001-04-30 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the decreasing production costs of IT systems, applications that had to be realised as expensive PCBs formerly, can now be realised as a system-on-chip. Furthermore, low cost broadband communication media for wide area communication as well as for the realisation of local distributed systems are available. Typically the market requires IT systems that realise a set of specific features for the end user in a given environment, so called embedded systems. Some examples for such embedded systems are control systems in cars, airplanes, houses or plants, information and communication devices like digital TV, mobile phones or autonomous systems like service- or edutainment robots. For the design of embedded systems the designer has to tackle three major aspects: The application itself including the man-machine interface, The (target) architecture of the system including all functional and non-functional constraints and, the design methodology including modelling, specification, synthesis, test and validation. The last two points are a major focus of this book. This book documents the high quality approaches and results that were presented at the International Workshop on Distributed and Parallel Embedded Systems (DIPES 2000), which was sponsored by the International Federation for Information Processing (IFIP), and organised by IFIP working groups WG10.3, WG10.4 and WG10.5. The workshop took place on October 18-19, 2000, in Schloß Eringerfeld near Paderborn, Germany. Architecture and Design of Distributed Embedded Systems is organised similar to the workshop. Chapters 1 and 4 (Methodology I and II) deal with different modelling and specification paradigms and the corresponding design methodologies. Generic system architectures for different classes of embedded systems are presented in Chapter 2. In Chapter 3 several design environments for the support of specific design methodologies are presented. Problems concerning test and validation are discussed in Chapter 5. The last two chapters include distribution and communication aspects (Chapter 6) and synthesis techniques for embedded systems (Chapter 7). This book is essential reading for computer science researchers and application developers.

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 Scheduling for Real Time Multiprocessor System written by Apurva Shah and published by LAP Lambert Academic Publishing. This book was released on 2014-07-11 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: A scheduling algorithm schedules a set of tasks in such way that the tasks are completed before their deadlines reached. There are varieties of algorithms for scheduling of periodic tasks on multiprocessor under partitioning scheme or global scheduling scheme. The most common scheduling algorithms are: Rate Monotonic (RM), Deadline Monotonic (DM), Earliest Deadline First (EDF) and Least Laxity First (LLF). In this book, we have proposed a new algorithm titled as D_EDF which is modified conventional EDF algorithm. The proposed algorithm along with EDF, LLF, RM, DM algorithms are simulated and tested for independent, preemptive, periodic tasks on tightly coupled real-time multiprocessor system under global scheduling. From experiments and result analysis it concludes that the proposed algorithm is very efficient in both underloaded and overloaded conditions. The algorithm proposed in this book; perform quite well during overloaded conditions. The algorithm is truly dynamic as it can work with available number of processors.

Download or read book Energy efficient Scheduling of Primary backup Tasks in Multiprocessor Real time Systems Extended Version written by Yifeng Guo and published by . This book was released on 2013 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the negative effects of the popular Dynamic Voltage and Frequency Scaling (DVFS) technique on transient faults being considered, the Primary/Backup approach has recently been exploited to save energy while preserving system reliability. In this paper, with the objectives of tolerating a single permanent fault and maintaining system reliability with respect to transient faults, we study energy-efficient dynamic-priority based scheduling algorithms for periodic Primary/Backup tasks on multiprocessor systems. Specifically, by separating primary and backup tasks on their dedicated processors, we first devise two schemes based on the idea of Standby-Sparing (SS): For Paired-SS, processors are organized as groups of two (i.e., pairs) and the existing SS scheme is applied within each pair of processors after partitioning tasks to the pairs. In Generalized-SS, processors are divided into two groups (of potentially different sizes), which are denoted as primary and secondary processor groups, respectively. The main (backup) tasks are scheduled on the primary (secondary) processor group under the partitioned-EDF (partitioned-EDL) with DVFS (DPM) to save energy. Next, instead of dedicating some processors to backup tasks, we propose schemes that allocate primary and backup tasks in a mixed manner to better utilize the slack time on all processors for more energy savings. On each processor, the Preference-Oriented Earliest Deadline (POED) scheduler is adopted to run primary tasks at scaled frequencies as soon as possible (ASAP) and backup tasks at the maximum frequency as late as possible (ALAP) to save energy. Online power management and recovery strategies are further discussed to address the problem with multiple permanent faults. Our empirical evaluations show that, for systems with a given number of processors, there normally exists an optimal configuration of primary and secondary groups for the Generalized-SS scheme, which leads to better energy savings compared to that of the Paired-SS scheme. Moreover, the POED-based schemes normally perform more stable and achieve better energy savings compared to those of the SS-based schemes.

Download or read book Efficient Near optimal Scheduling of Multiprocessor Systems written by Marc Thomas Kaufman and published by . This book was released on 1973 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scheduling in Real Time Systems written by Francis Cottet and published by Wiley. This book was released on 2002-11-22 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt: * Real-time systems are used in a wide range of applications, including command and control systems, flight control, telecommunication systems, and online purchase payment * Provides an accessible yet comprehensive treatment * of real-time computing and communications systems * Outlines the basics of real-time scheduling and scheduling policies designed for real-time applications * Each chapter contains examples and case studies along with test exercises and solutions

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 Energy Efficient Scheduling for Real time Systems written by Nikhil Gupta and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this dissertation is to extend the state of the art in real-time scheduling algorithms to achieve energy efficiency. Currently, Pfair scheduling is one of the few scheduling frameworks which can optimally schedule a periodic real-time taskset on a multiprocessor platform. Despite the theoretical optimality, there exist large concerns about efficiency and applicability of Pfair scheduling in practical situations. This dissertation studies and proposes solutions to such efficiency and applicability concerns. This dissertation also explores temperature aware energy management in the domain of real-time scheduling. The thesis of this dissertation is: the implementation efficiency of Pfair scheduling algorithms can be improved. Further, temperature awareness of a real-time system can be improved while considering variation of task execution times to reduce energy consumption. This thesis is established through research in a number of directions. First, we explore the applicability of Dynamic Voltage and Frequency Scaling (DVFS) feature in the underlying platform, within Pfair scheduled systems. We propose techniques to reduce energy consumption in Pfair scheduling by using DVFS. Next, we explore the problem of quantum size selection in Pfair scheduled system so that runtime overheads are minimized. We also propose a hardware design for a central Pfair scheduler core in a multiprocessor system to minimized the overheads and energy consumption of Pfair scheduling. Finally, we propose a temperature aware energy management scheme for tasks with varying execution times.

Download or read book Energy efficient Scheduling Algorithms for Real time Systems written by Hui Cheng and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Dynamic Scheduling for Real Time Systems written by Apurva Shah and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Resource Management in Real time Systems and Networks written by C. Siva Ram Murthy and published by MIT Press. This book was released on 2001 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces the concepts and state-of-the-art research developments of resource management in real-time systems and networks. Real-time systems and networks are of increasing importance in many applications, including automated factories, telecommunication systems, defense systems, and space systems. This book introduces the concepts and state-of-the-art research developments of resource management in real-time systems and networks. Unlike other texts in the field, it covers the entire spectrum of issues in resource management, including task scheduling in uniprocessor real-time systems; task scheduling, fault-tolerant task scheduling, and resource reclaiming in multiprocessor real-time systems; conventional task scheduling and object-based task scheduling in distributed real-time systems; message scheduling; QoS routing; dependable communication; multicast communication; and medium access protocols in real-time networks. It provides algorithmic treatments for all of the issues addressed, highlighting the intuition behind each algorithm and giving examples. The book also includes two chapters of case studies.

Download or read book Handbook of Scheduling written by Joseph Y-T. Leung and published by CRC Press. This book was released on 2004-04-27 with total page 1215 pages. Available in PDF, EPUB and Kindle. Book excerpt: This handbook provides full coverage of the most recent and advanced topics in scheduling, assembling researchers from all relevant disciplines to facilitate new insights. Presented in six parts, these experts provides introductory material, complete with tutorials and algorithms, then examine classical scheduling problems. Part 3 explores scheduling models that originate in areas such as computer science, operations research. The following section examines scheduling problems that arise in real-time systems. Part 5 discusses stochastic scheduling and queueing networks, and the final section discusses a range of applications in a variety of areas, from airlines to hospitals.