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 Scratchpad Memory Management for Multicore Real time Embedded Systems written by Saud Wasly and published by . This book was released on 2018 with total page 227 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multicore systems will continue to spread in the domain of real-time embedded systems due to the increasing need for high-performance applications. This research discusses some of the challenges associated with employing multicore systems for safety-critical real-time applications. Mainly, this work is concerned with providing: 1) efficient inter-core timing isolation for independent tasks, and 2) predictable task communication for communicating tasks. Principally, we introduce a new task execution model, based on the 3-phase execution model, that exploits the Direct Memory Access (DMA) controllers available in modern embedded platforms along with ScratchPad Memories (SPMs) to enforce strong timing isolation between tasks. The DMA and the SPMs are explicitly managed to pre-load tasks from main memory into the local (private) scratchpad memories. Tasks are then executed from the local SPMs without accessing main memory. This model allows CPU execution to be overlapped with DMA loading/unloading operations from and to main memory. We show that by co-scheduling task execution on CPUs and using DMA to access memory and I/O, we can efficiently hide access latency to physical resources. In turn, this leads to significant improvements in system schedulability, compared to both the case of unregulated contention for access to physical resources and to previous cache and SPM management techniques for real-time systems. The presented SPM-centric scheduling algorithms and analyses cover single-core, partitioned, and global real-time systems. The proposed scheme is also extended to support large tasks that do not fit entirely into the local SPM. Moreover, the schedulability analysis considers the case of recovering from transient soft errors (bit flips caused by a single event upset) in several levels of memories, that cannot be automatically corrected in hardware by the ECC unit. The proposed SPM-centric scheduling is integrated at the OS level; thus it is transparent to applications. The proposed scheme is implemented and evaluated on an FPGA platform and a Commercial-Off-The-Shelf (COTS) platform. In regards to real-time task communication, two types of communication are considered. 1) Asynchronous inter-task communication, between either sequential tasks (single-threaded) or parallel tasks (multi-threaded). 2) Intra-task communication, where parallel threads of the same application exchange data. A new task scheduling model for parallel tasks (Bundled Scheduling) is proposed to facilitate intra-task communication and reduce synchronization overheads. We show that the proposed bundled scheduling model can be applied to several parallel programming models, such as fork-join and DAG-based applications, leading to improved system schedulability. Finally, intra-task communication is governed by a predictable inter-core communication platform. Specifically, we propose HopliteRT, a lean and predictable Network-on-Chip that connects the private SPMs.

Download or read book Efficient Scheduling and Analysis Techniques for Supporting Real time Cyber physical Applications and Systems written by Zheng Dong and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: To guarantee predictable temporal correctness in multicore systems, a difficult problem is to analyze the execution behaviors of tasks that may access heterogeneous resources including both CPU cores and shared resources (e.g., memory or accelerators). A traditional approach is to analyze schedulability from a core-centric perspective. The core-centric perspective is sound for traditional embedded systems where computing resources may be insufficient while the contention on shared resources is often light. However, it is not applicable to many CPS supporting rather resource-demanding workloads. Due to the large number of physical components involved, the operations of CPS include sensing, processing and storage of massive big data. In most CPS, such as the autonomous driving system, shared resources such as memory may become the actual scheduling bottleneck, causing the worst-case latency bound on the shared resource to be rather pessimistic or even impossible to bound. Motivated by this observation, we argue that it may be much more viable to resolve this multi-resource scheduling problem from the counter-intuitive shared-resource centric perspective since tasks may experience much lighter contention on CPU cores. In my PhD dissertation, I resolve the above-discussed multi-resource scheduling problem from the shared-resource-centric perspective, which brings new challenges in analyzing real-time task systems. For instance, traditionally, each task executes sequentially on one processor, but on shared resources, the number of processors simultaneously used by a task can be greater than one (i.e., parallelism). Moreover, tasks can execute continuously and preemptively on CPUs, but on shared resources, a task may experience suspension delays on the CPU cores due to accessing shared resources and may need to execute in a non- or limited-preemptive manner. My research seeks to resolve these hard challenges. Specifically, my developed techniques focus on judiciously scheduling tasks that may exhibit parallel execution and self-suspension behaviors on the limited-preemptive shared resource. Our research methodology is counter-intuitive yet efficient: we treat the shared resource as the first-class units and bound the worst-case latency a task may experience on the CPU cores (i.e., treating CPU cores as “I/O”). Interestingly, some practical issues in CPS can be solved properly using real-time scheduling theory. In my PhD dissertation, I have developed several scheduling techniques to analyze CPS in different scenarios, providing predictable latency performance to end users.

Download or read book Real time Systems Scheduling 1 written by Maryline Chetto and published by John Wiley & Sons. This book was released on 2014-11-17 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: Real-time systems are used in a wide range of applications, including control, sensing, multimedia, etc. Scheduling is a central problem for these computing/communication systems since responsible of software execution in a timely manner. This book provides state of knowledge in this domain with special emphasis on the key results obtained within the last decade. This book addresses foundations as well as the latest advances and findings in Real-Time Scheduling, giving all references to important papers. But nevertheless the chapters will be short and not overloaded with confusing details. Coverage includes scheduling approaches for mono-core as well as multi-core platforms, dependent tasks, networks, and notably very tremendous recent advances in scheduling of energy constrained embedded systems. Other sophisticated issues such as feedback control scheduling and timing analysis of critical applications are also addressed. This volume can serve as a textbook for courses on the topic in bachelor and in more advanced master programs. It also provides a reference for computer scientists and engineers involved in the design or the development of Cyber-Physical Systems which require up-to-date real-time scheduling solutions.

Download or read book Robust Scheduling of Real time Applications on Efficient Embedded Multicore Systems written by Michael Deubzer and published by . This book was released on 2011 with total page 0 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 Systems Development with RTEMS and Multicore Processors written by Gedare Bloom and published by CRC Press. This book was released on 2020-11-22 with total page 535 pages. Available in PDF, EPUB and Kindle. Book excerpt: The proliferation of multicore processors in the embedded market for Internet-of-Things (IoT) and Cyber-Physical Systems (CPS) makes developing real-time embedded applications increasingly difficult. What is the underlying theory that makes multicore real-time possible? How does theory influence application design? When is a real-time operating system (RTOS) useful? What RTOS features do applications need? How does a mature RTOS help manage the complexity of multicore hardware? Real-Time Systems Development with RTEMS and Multicore Processors answers these questions and more with exemplar Real-Time Executive for Multiprocessor Systems (RTEMS) RTOS to provide concrete advice and examples for constructing useful, feature-rich applications. RTEMS is free, open-source software that supports multi-processor systems for over a dozen CPU architectures and over 150 specific system boards in applications spanning the range of IoT and CPS domains such as satellites, particle accelerators, robots, racing motorcycles, building controls, medical devices, and more. The focus of this book is on enabling real-time embedded software engineering while providing sufficient theoretical foundations and hardware background to understand the rationale for key decisions in RTOS and application design and implementation. The topics covered in this book include: Cross-compilation for embedded systems development Concurrent programming models used in real-time embedded software Real-time scheduling theory and algorithms used in wide practice Usage and comparison of two application programmer interfaces (APIs) in real-time embedded software: POSIX and the RTEMS Classic APIs Design and implementation in RTEMS of commonly found RTOS features for schedulers, task management, time-keeping, inter-task synchronization, inter-task communication, and networking The challenges introduced by multicore hardware, advances in multicore real-time theory, and software engineering multicore real-time systems with RTEMS All the authors of this book are experts in the academic field of real-time embedded systems. Two of the authors are primary open-source maintainers of the RTEMS software project.

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 Efficient Scheduling on Multiprogrammed Shared memory Multiprocessors written by Andrew Tucker and published by . This book was released on 1993 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis explores using more sophisticated scheduling systems to avoid these problems. Robust implementations of previously proposed approaches involving cache affinity scheduling and gang scheduling are developed and evaluated. It then presents the design, implementation, and performance of process control, a novel scheduling approach using explicit cooperation between the application and kernel to minimize context switching. Performance results from a suite of workloads containing both serial and parallel applications, run on a 4-processor Silicon Graphics workstation, confirm the effectiveness of the process control approach.

Download or read book Memory Controllers for Real Time Embedded Systems written by Benny Akesson and published by Springer Science & Business Media. This book was released on 2011-09-15 with total page 235 pages. Available in PDF, EPUB and Kindle. Book excerpt: Verification of real-time requirements in systems-on-chip becomes more complex as more applications are integrated. Predictable and composable systems can manage the increasing complexity using formal verification and simulation. This book explains the concepts of predictability and composability and shows how to apply them to the design and analysis of a memory controller, which is a key component in any real-time system.

Download or read book Self Organization in Embedded Real Time Systems written by M. Teresa Higuera-Toledano and published by Springer Science & Business Media. This book was released on 2012-11-09 with total page 215 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the emerging field of self-organizing, multicore, distributed and real-time embedded systems. Self ‐organization of both hardware and software can be a key technique to handle the growing complexity of modern computing systems. Distributed systems running hundreds of tasks on dozens of processors, each equipped with multiple cores, requires self‐organization principles to ensure efficient and reliable operation. This book addresses various, so-called Self‐X features such as self-configuration, self‐optimization, self‐adaptation, self‐healing and self‐protection.

Download or read book Power Efficient Scheduling for Hard Real time Systems on a Multiprocessor Platform written by Peter Joseph Nistler and published by . This book was released on 2009 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Static and Dynamic Scheduling for Effective Use of Multicore Systems written by Fengguang Song and published by . This book was released on 2009 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multicore systems have increasingly gained importance in high performance computers. Compared to the traditional microarchitectures, multicore architectures have a simpler design, higher performance-to-area ratio, and improved power efficiency. Although the multicore architecture has various advantages, traditional parallel programming techniques do not apply to the new architecture efficiently. This dissertation addresses how to determine optimized thread schedules to improve data reuse on shared-memory multicore systems and how to seek a scalable solution to designing parallel software on both shared-memory and distributed-memory multicore systems. We propose an analytical cache model to predict the number of cache misses on the time-sharing L2 cache on a multicore processor. The model provides an insight into the impact of cache sharing and cache contention between threads. Inspired by the model, we build the framework of affinity based thread scheduling to determine optimized thread schedules to improve data reuse on all the levels in a complex memory hierarchy. The affinity based thread scheduling framework includes a model to estimate the cost of a thread schedule, which consists of three submodels: an affinity graph submodel, a memory hierarchy submodel, and a cost submodel. Based on the model, we design a hierarchical graph partitioning algorithm to determine near-optimal solutions. We have also extended the algorithm to support threads with data dependences. The algorithms are implemented and incorporated into a feedback directed optimization prototype system. The prototype system builds upon a binary instrumentation tool and can improve program performance greatly on shared-memory multicore architectures. We also study the dynamic data-availability driven scheduling approach to designing new parallel software on distributed-memory multicore architectures. We have implemented a decentralized dynamic runtime system. The design of the runtime system is focused on the scalability metric. At any time only a small portion of a task graph exists in memory. We propose an algorithm to solve data dependences without process cooperation in a distributed manner. Our experimental results demonstrate the scalability and practicality of the approach for both shared-memory and distributed-memory multicore systems. Finally, we present a scalable nonblocking topology-aware multicast scheme for distributed DAG scheduling applications.

Download or read book Task Scheduling for Multi core and Parallel Architectures written by Quan Chen and published by Springer. This book was released on 2017-11-23 with total page 251 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents task-scheduling techniques for emerging complex parallel architectures including heterogeneous multi-core architectures, warehouse-scale datacenters, and distributed big data processing systems. The demand for high computational capacity has led to the growing popularity of multicore processors, which have become the mainstream in both the research and real-world settings. Yet to date, there is no book exploring the current task-scheduling techniques for the emerging complex parallel architectures. Addressing this gap, the book discusses state-of-the-art task-scheduling techniques that are optimized for different architectures, and which can be directly applied in real parallel systems. Further, the book provides an overview of the latest advances in task-scheduling policies in parallel architectures, and will help readers understand and overcome current and emerging issues in this field.

Download or read book Job Scheduling Strategies for Parallel Processing written by Dalibor Klusáček and published by Springer Nature. This book was released on 2020-11-16 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the thoroughly refereed post-conference proceedings of the 23rd International Workshop on Job Scheduling Strategies for Parallel Processing, JSSPP 2020, held in New Orleans, LA, USA, in May 2020.* The 6 revised full papers presented were carefully reviewed and selected from 8 submissions. In addition to this, one invited paper and one keynote pare were included in the workshop. The papers cover topics within the fields of resource management and scheduling. They focus on several interesting problems such as resource contention and workload interference, new scheduling policy, scheduling ultrasound simulation workflows, and walltime prediction. * The conference was held virtually due to the COVID-19 pandemic.

Download or read book Fuzzy Logic Based Power Efficient Real Time Multi Core System written by Jameel Ahmed and published by Springer. This book was released on 2016-11-15 with total page 69 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on identifying the performance challenges involved in computer architectures, optimal configuration settings and analysing their impact on the performance of multi-core architectures. Proposing a power and throughput-aware fuzzy-logic-based reconfiguration for Multi-Processor Systems on Chip (MPSoCs) in both simulation and real-time environments, it is divided into two major parts. The first part deals with the simulation-based power and throughput-aware fuzzy logic reconfiguration for multi-core architectures, presenting the results of a detailed analysis on the factors impacting the power consumption and performance of MPSoCs. In turn, the second part highlights the real-time implementation of fuzzy-logic-based power-efficient reconfigurable multi-core architectures for Intel and Leone3 processors.