Download or read book Precise Energy Efficient Scheduling of Mixed criticality Tasks Sustainable Mixed criticality Scheduling written by Sai Sruti and published by . This book was released on 2018 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: "In this thesis, the imprecise mixed-criticality model (IMC) is extended to precise scheduling of tasks, and integrated with the dynamic voltage and frequency scaling (DVFS) technique to enable energy minimization. The challenge in precise scheduling of MC systems is to simultaneously guarantee the timing correctness for all tasks, hi and lo, under both pessimistic and optimistic (less pessimistic) assumptions. To the best of knowledge this is the first work to address the integration of DVFS energy conserving techniques with precise scheduling of lo-tasks of the MC model. In this thesis, the utilization based schedulability tests and sufficient conditions for such systems under Earliest Deadline First EDF-VD scheduling policy are presented. Quantitative study in the forms of speedup bound and approximation ratio are also proved for the unified model. Extensive experimental studies are conducted to verify the theoretical results as well as the effectiveness of the proposed algorithm. In safety- critical systems, it is essential to perform schedulability analysis prior to run-time. Parameters characterizing the run-time workload are generated by pessimistic techniques; hence, adopting conservative estimates may result in systems performing much better than anticipated during run-time. This thesis also addresses the following questions associated to the better performance of the task system: (i) How does parameter change affect the schedulability of a task set (system)? (ii) In the event that a mixed-criticality system design is deemed schedulable and specific part/parts of the system are reassigned to be of low-criticality, is the system still safe to run? (iii) If a system is presumed to be non-schedulable, does it invariably benefit to reduce the criticality of some task? To answer these questions, in this thesis, we not only study the property of sustainability with regards to criticality levels, but also revisit sustainability of several uniprocessor and multiprocessor scheduling policies with respect to other parameters"--Abstract, page iii.

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 Mixed criticality Real time Task Scheduling with Graceful Degradation written by Samsil Arefin and published by . This book was released on 2018 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The mixed-criticality real-time systems implement functionalities of different degrees of importance (or criticalities) upon a shared platform. In traditional mixed-criticality systems, under a hi mode switch, no guaranteed service is provided to lo-criticality tasks. After a mode switch, only hi-criticality tasks are considered for execution while no guarantee is made to the lo-criticality tasks. However, with careful optimistic design, a certain degree of service guarantee can be provided to lo-criticality tasks upon a mode switch. This concept is broadly known as graceful degradation. Guaranteed graceful degradation provides a better quality of service as well as it utilizes the system resource more efficiently. In this thesis, we study two efficient techniques of graceful degradation. First, we study a mixed-criticality scheduling technique where graceful degradation is provided in the form of minimum cumulative completion rates. We present two easy-to-implement admission-control algorithms to determine which lo-criticality jobs to complete in hi mode. The scheduling is done by following deadline virtualization, and two heuristics are shown for virtual deadline settings. We further study the schedulability analysis and the backward mode switch conditions, which are proposed and proved in (Guo et al., 2018). Next, we present a probabilistic scheduling technique for mixed-criticality tasks on multiprocessor systems where a system-wide permitted failure probability is known. The schedulability conditions are derived along with the processor allocation scheme. The work is extended from (Guo et al., 2015), where the probabilistic model is first introduced for independent task scheduling on a uniprocessor platform. We further consider the failure dependency between tasks while scheduling on multiprocessor platforms. We provide related theoretical analysis to show the correctness of our work. To show the effectiveness of our proposed techniques, we conduct a detailed experimental evaluation under different circumstances"--Abstract, page iii.

Download or read book Schedulability in Mixed criticality Systems written by Rany Kahil and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Real-time safety-critical systems must complete their tasks within a given time limit. Failure to successfully perform their operations, or missing a deadline, can have severe consequences such as destruction of property and/or loss of life. Examples of such systems include automotive systems, drones and avionics among others. Safety guarantees must be provided before these systems can be deemed usable. This is usually done through certification performed by a certification authority.Safety evaluation and certification are complicated and costly even for smaller systems.One answer to these difficulties is the isolation of the critical functionality. Executing tasks of different criticalities on separate platforms prevents non-critical tasks from interfering with critical ones, provides a higher guaranty of safety and simplifies the certification process limiting it to only the critical functions. But this separation, in turn, introduces undesirable results portrayed by an inefficient resource utilization, an increase in the cost, weight, size and energy consumption which can put a system in a competitive disadvantage.To overcome the drawbacks of isolation, Mixed Criticality (MC) systems can be used. These systems allow functionalities with different criticalities to execute on the same platform. In 2007, Vestal proposed a model to represent MC-systems where tasks have multiple Worst Case Execution Times (WCETs), one for each criticality level. In addition, correctness conditions for scheduling policies were formally defined, allowing lower criticality jobs to miss deadlines or be even dropped in cases of failure or emergency situations.The introduction of multiple WCETs and different conditions for correctness increased the difficulty of the scheduling problem for MC-systems. Conventional scheduling policies and schedulability tests proved inadequate and the need for new algorithms arose. Since then, a lot of work has been done in this field.In this thesis, we contribute to the study of schedulability in MC-systems. The workload of a system is represented as a set of jobs that can describe the execution over the hyper-period of tasks or over a duration in time. This model allows us to study the viability of simulation-based correctness tests in MC-systems. We show that simulation tests can still be used in mixed-criticality systems, but in this case, the schedulability of the worst case scenario is no longer sufficient to guarantee the schedulability of the system even for the fixed priority scheduling case. We show that scheduling policies are not predictable in general, and define the concept of weak-predictability for MC-systems. We prove that a specific class of fixed priority policies are weakly predictable and propose two simulation-based correctness tests that work for weakly-predictable policies.We also demonstrate that contrary to what was believed, testing for correctness can not be done only through a linear number of preemptions.The majority of the related work focuses on systems of two criticality levels due to the difficulty of the problem. But for automotive and airborne systems, industrial standards define four or five criticality levels, which motivated us to propose a scheduling algorithm that schedules mixed-criticality systems with theoretically any number of criticality levels. We show experimentally that it has higher success rates compared to the state of the art.We illustrate how our scheduling algorithm, or any algorithm that generates a single time-triggered table for each criticality mode, can be used as a recovery strategy to ensure the safety of the system in case of certain failures.Finally, we propose a high level concurrency language and a model for designing an MC-system with coarse grained multi-core interference.

Download or read book Scheduling of Certifiable Mixed criticality Systems written by Dario Socci and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modern real-time systems tend to be mixed-critical, in the sense that they integrate on the same computational platform applications at different levels of criticality. Integration gives the advantages of reduced cost, weight and power consumption, which can be crucial for modern applications like Unmanned Aerial Vehicles (UAVs). On the other hand, this leads to major complications in system design. Moreover, such systems are subject to certification, and different criticality levels needs to be certified at different level of assurance. Among other aspects, the real-time scheduling of certifiable mixed critical systems has been recognized to be a challenging problem. Traditional techniques require complete isolation between criticality levels or global certification to the highest level of assurance, which leads to resource waste, thus loosing the advantage of integration. This led to a novel wave of research in the real-time community, and many solutions were proposed. Among those, one of the most popular methods used to schedule such systems is Audsley approach. However this method has some limitations, which we discuss in this thesis. These limitations are more pronounced in the case of multiprocessor scheduling. In this case priority-based scheduling looses some important properties. For this reason scheduling algorithms for multiprocessor mixed-critical systems are not as numerous in literature as the single processor ones, and usually are built on restrictive assumptions. This is particularly problematic since industrial real-time systems strive to migrate from single-core to multi-core and many-core platforms. Therefore we motivate and study a different approach that can overcome these problems.A restriction of practical usability of many mixed-critical and multiprocessor scheduling algorithms is assumption that jobs are independent. In reality they often have precedence constraints. In the thesis we show the mixed-critical variant of the problem formulation and extend the system load metrics to the case of precedence-constraint task graphs. We also show that our proposed methodology and scheduling algorithm MCPI can be extended to the case of dependent jobs without major modification and showing similar performance with respect to the independent jobs case. Another topic we treated in this thesis is time-triggered scheduling. This class of schedulers is important because they considerably reduce the uncertainty of job execution intervals thus simplifying the safety-critical system certification. They also simplify any auxiliary timing-based analyses that may be required to validate important extra-functional properties in embedded systems, such as interference on shared buses and caches, peak power dissipation, electromagnetic interference etc..The trivial method of obtaining a time-triggered schedule is simulation of the worst-case scenario in event-triggered algorithm. However, when applied directly, this method is not efficient for mixed-critical systems, as instead of one worst-case scenario they have multiple corner-case scenarios. For this reason, it was proposed in the literature to treat all scenarios into just a few tables, one per criticality mode. We call this scheduling approach Single Time Table per Mode (STTM) and propose a contribution in this context. In fact we introduce a method that transforms practically any scheduling algorithm into an STTM one. It works optimally on single core and shows good experimental results for multi-cores.Finally we studied the problem of the practical realization of mixed critical systems. Our effort in this direction is a design flow that we propose for multicore mixed critical systems. In this design flow, as the model of computation we propose a network of deterministic multi-periodic synchronous processes. Our approach is demonstrated using a publicly available toolset, an industrial application use case and a multi-core platform.

Download or read book An Elastic Mixed criticality Task Model and Early release EDF Scheduling Algorithms written by Hang Su and published by . This book was released on 2016 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many algorithms have recently been studied for scheduling mixed-criticality (MC) tasks. However, most existing MC scheduling algorithms guarantee the timely executions of high-criticality (HC) tasks at the expense of discarding low-criticality (LC) tasks, which can cause serious service interruption for such tasks. In this work, aiming at providing guaranteed services for LC tasks, we study an Elastic Mixed-Criticality (E-MC) task model for dual-criticality systems. Specifically, the model allows each LC task to specify its maximum period (i.e., minimum service level) and a set of early-release points. We propose an Early-Release (ER) mechanism that enables LC tasks be released more frequently and thus improve their service levels at runtime, with both conservative and aggressive approaches to exploiting system slack being considered, which is applied to both EDF and preference-oriented earliest-deadline (POED) schedulers. We formally prove the correctness of the proposed ER-EDF scheduler on guaranteeing the timeliness of all tasks through judicious management of the early releases of LC tasks. The proposed model and schedulers are evaluated through extensive simulations. The results show that, by moderately relaxing the service requirements of LC tasks in MC task sets (i.e., by having LC tasks' maximum periods in the E-MC model be 2 to 3 times of their desired MC periods), most transformed E-MC task sets can be successfully scheduled without sacrificing the timeliness of HC tasks. Moreover, with the proposed ER mechanism, the runtime performance of tasks (e.g., execution frequencies of LC tasks, response times and jitters of HC tasks) can be significantly improved under the ER schedulers when compared to that of the state-of-the-art EDF-VD scheduler.

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 Critical Materials Strategy written by Steven Chu and published by DIANE Publishing. This book was released on 2011-05 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report examines the role of rare earth metals and other materials in the clean energy economy. It was prepared by the U.S. Department of Energy (DoE) based on data collected and research performed during 2010. In the report, DoE describes plans to: (1) develop its first integrated research agenda addressing critical materials, building on three technical workshops convened by the DoE during November and December 2010; (2) strengthen its capacity for information-gathering on this topic; and (3) work closely with international partners, including Japan and Europe, to reduce vulnerability to supply disruptions and address critical material needs. Charts and tables. This is a print on demand report.

Download or read book Principles of Modeling written by Marten Lohstroh and published by Springer. This book was released on 2018-07-19 with total page 564 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Festschrift is published in honor of Edward A. Lee, Robert S. Pepper Distinguished Professor Emeritus and Professor in the Graduate School in the Department of Electrical Engineering and Computer Sciences at the University of California, Berkeley, USA, on the occasion of his 60th birthday. The title of this Festschrift is “Principles of Modeling" because Edward A. Lee has long been devoted to research that centers on the role of models in science and engineering. He has been examining the use and limitations of models, their formal properties, their role in cognition and interplay with creativity, and their ability to represent reality and physics. The Festschrift contains 29 papers that feature the broad range of Edward A. Lee’s research topics; such as embedded systems; real-time computing; computer architecture; modeling and simulation, and systems design.

Download or read book Fault Tolerant Systems written by Israel Koren and published by Elsevier. This book was released on 2010-07-19 with total page 399 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fault-Tolerant Systems is the first book on fault tolerance design with a systems approach to both hardware and software. No other text on the market takes this approach, nor offers the comprehensive and up-to-date treatment that Koren and Krishna provide. This book incorporates case studies that highlight six different computer systems with fault-tolerance techniques implemented in their design. A complete ancillary package is available to lecturers, including online solutions manual for instructors and PowerPoint slides. Students, designers, and architects of high performance processors will value this comprehensive overview of the field. - The first book on fault tolerance design with a systems approach - Comprehensive coverage of both hardware and software fault tolerance, as well as information and time redundancy - Incorporated case studies highlight six different computer systems with fault-tolerance techniques implemented in their design - Available to lecturers is a complete ancillary package including online solutions manual for instructors and PowerPoint slides

Download or read book Our Common Future written by and published by . This book was released on 1990 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Soft Real Time Systems Predictability vs Efficiency written by Giorgio C Buttazzo and published by Springer Science & Business Media. This book was released on 2006-07-02 with total page 281 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hard real-time systems are very predictable, but not sufficiently flexible to adapt to dynamic situations. They are built under pessimistic assumptions to cope with worst-case scenarios, so they often waste resources. Soft real-time systems are built to reduce resource consumption, tolerate overloads and adapt to system changes. They are also more suited to novel applications of real-time technology, such as multimedia systems, monitoring apparatuses, telecommunication networks, mobile robotics, virtual reality, and interactive computer games. This unique monograph provides concrete methods for building flexible, predictable soft real-time systems, in order to optimize resources and reduce costs. It is an invaluable reference for developers, as well as researchers and students in Computer Science.

Download or read book High Performance Computing HiPC 2007 written by Srinivas Aluru and published by Springer. This book was released on 2008-01-22 with total page 687 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the refereed proceedings of the 14th International Conference on High-Performance Computing, HiPC 2007, held in Goa, India, in December 2007. The 53 revised full papers presented together with the abstracts of five keynote talks were carefully reviewed and selected from 253 submissions. The papers are organized in topical sections on a broad range of applications including I/O and FPGAs, and microarchitecture and multiprocessor architecture.

Download or read book Embedded System Design written by Peter Marwedel and published by Springer Science & Business Media. This book was released on 2010-11-16 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: Until the late 1980s, information processing was associated with large mainframe computers and huge tape drives. During the 1990s, this trend shifted toward information processing with personal computers, or PCs. The trend toward miniaturization continues and in the future the majority of information processing systems will be small mobile computers, many of which will be embedded into larger products and interfaced to the physical environment. Hence, these kinds of systems are called embedded systems. Embedded systems together with their physical environment are called cyber-physical systems. Examples include systems such as transportation and fabrication equipment. It is expected that the total market volume of embedded systems will be significantly larger than that of traditional information processing systems such as PCs and mainframes. Embedded systems share a number of common characteristics. For example, they must be dependable, efficient, meet real-time constraints and require customized user interfaces (instead of generic keyboard and mouse interfaces). Therefore, it makes sense to consider common principles of embedded system design. Embedded System Design starts with an introduction into the area and a survey of specification models and languages for embedded and cyber-physical systems. It provides a brief overview of hardware devices used for such systems and presents the essentials of system software for embedded systems, like real-time operating systems. The book also discusses evaluation and validation techniques for embedded systems. Furthermore, the book presents an overview of techniques for mapping applications to execution platforms. Due to the importance of resource efficiency, the book also contains a selected set of optimization techniques for embedded systems, including special compilation techniques. The book closes with a brief survey on testing. Embedded System Design can be used as a text book for courses on embedded systems and as a source which provides pointers to relevant material in the area for PhD students and teachers. It assumes a basic knowledge of information processing hardware and software. Courseware related to this book is available at http://ls12-www.cs.tu-dortmund.de/~marwedel.

Download or read book Silicon Photonics for High Performance Computing and Beyond written by Mahdi Nikdast and published by CRC Press. This book was released on 2021-11-16 with total page 391 pages. Available in PDF, EPUB and Kindle. Book excerpt: Silicon photonics is beginning to play an important role in driving innovations in communication and computation for an increasing number of applications, from health care and biomedical sensors to autonomous driving, datacenter networking, and security. In recent years, there has been a significant amount of effort in industry and academia to innovate, design, develop, analyze, optimize, and fabricate systems employing silicon photonics, shaping the future of not only Datacom and telecom technology but also high-performance computing and emerging computing paradigms, such as optical computing and artificial intelligence. Different from existing books in this area, Silicon Photonics for High-Performance Computing and Beyond presents a comprehensive overview of the current state-of-the-art technology and research achievements in applying silicon photonics for communication and computation. It focuses on various design, development, and integration challenges, reviews the latest advances spanning materials, devices, circuits, systems, and applications. Technical topics discussed in the book include: • Requirements and the latest advances in high-performance computing systems • Device- and system-level challenges and latest improvements to deploy silicon photonics in computing systems • Novel design solutions and design automation techniques for silicon photonic integrated circuits • Novel materials, devices, and photonic integrated circuits on silicon • Emerging computing technologies and applications based on silicon photonics Silicon Photonics for High-Performance Computing and Beyond presents a compilation of 19 outstanding contributions from academic and industry pioneers in the field. The selected contributions present insightful discussions and innovative approaches to understand current and future bottlenecks in high-performance computing systems and traditional computing platforms, and the promise of silicon photonics to address those challenges. It is ideal for researchers and engineers working in the photonics, electrical, and computer engineering industries as well as academic researchers and graduate students (M.S. and Ph.D.) in computer science and engineering, electronic and electrical engineering, applied physics, photonics, and optics.

Download or read book Fault tolerant Computer System Design written by Dhiraj K. Pradhan and published by Prentice Hall. This book was released on 1996 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the ten years since the publication of the first edition of this book, the field of fault-tolerant design has broadened in appeal, particularly with its emerging application in distributed computing. This new edition specifically deals with this dynamically changing computing environment, incorporating new topics such as fault-tolerance in multiprocessor and distributed systems.

Download or read book The Cross Entropy Method written by Reuven Y. Rubinstein and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rubinstein is the pioneer of the well-known score function and cross-entropy methods. Accessible to a broad audience of engineers, computer scientists, mathematicians, statisticians and in general anyone, theorist and practitioner, who is interested in smart simulation, fast optimization, learning algorithms, and image processing.