共查询到20条相似文献,搜索用时 21 毫秒
1.
嵌入式实时系统通常被实现为多任务系统,以满足多个外部输入的响应时间的最后期限约束。Linux内核中已经实现了基于EDF(Earliest Deadline First)调度算法的DL调度器,使得实时任务能在截止期限内运行完成。但对于多核处理器,由于实时任务在EDF算法下会出现Dhall效应,论文对 Linux内核中实时任务调度算法进行了改进。在EDF算法的基础上,实现LLF(Least Laxity First)调度算法并对其加以改进,通过降低任务上下文切换频率以及减少松弛度的计算来减小调度过程中的颠簸现象。实验证明该方法既避免了Dhall效应,又减少了任务上下文切换带来的系统开销,并使得任务能在截止期限内完成调度,取得了较好的调度性能。 相似文献
2.
针对当前嵌入式系统中时间触发与事件触发混合任务的特点,以μC/OS-II操作系统架构为基础,设计了一种能够同时支持时间触发与事件触发的混合操作系统内核架构。该架构符合OSEK/VDX标准,具有良好的可移植性。针对混合任务调度问题,提出了一种静态周期性可抢占式混合任务调度策略,该策略同时支持中断级与任务级的任务切换,并采用EDF(最早截止时间优先)算法对被抢占的时间触发任务进行恢复,相比OSEKtime OS只能在中断级进行任务切换以及FIFO(先进先出)恢复算法,能够提高系统资源利用率,并最大限度保证任务实时性。实验分析结果表明,所设计的混合操作系统架构移植方便,所提出的混合任务调度策略可行有效,调度过程具有良好的可预测性。 相似文献
3.
基于Linux内核的实时调度机制研究及实现 总被引:3,自引:0,他引:3
分析了Linux操作系统内核提供的软实时调度机制及其存在的问题,阐述了基于Linux内核构建实时Linux操作系统的技术方案。着重介绍了RTLinux实时内核的结构框架,并对RTLinux的中断处理机制与调度机制进行了设计与实现。 相似文献
4.
支持服务质量的Linux内核设计与实现 总被引:1,自引:0,他引:1
Linux操作系统对实时QoS支持较弱,但具有很好的实时应用前景。本文选择对Linux在内核级进行QoS扩展。利用Linux进程管理策略与机制分离的设计风格,设计了一个内核级的支持QoS的实时调度器。不需要修改应用,就能满足应用的QoS需求。选择EDF实时调度算法作为扩展目标,引入了“预留”对象这一数据结构,实现了进程间的共享QoS。该新的Linux内核能更好地支持QoS,满足了实时系统的QoS需求。 相似文献
5.
Exact quantification of the sub-optimality of uniprocessor fixed priority pre-emptive scheduling 总被引:1,自引:1,他引:0
This paper examines the relative effectiveness of fixed priority pre-emptive scheduling in a uniprocessor system, compared
to an optimal algorithm such as Earliest Deadline First (EDF).
The quantitative metric used in this comparison is the processor speedup factor, equivalent to the factor by which processor
speed needs to increase to ensure that any taskset that is schedulable according to an optimal scheduling algorithm can be
scheduled using fixed priority pre-emptive scheduling, assuming an optimal priority assignment policy. 相似文献
6.
Autonomous and semi-autonomous mobile robots have to perform a multiplicity of concurrent activities in order to carry out useful tasks in unstructured human-populated environments. Even if it is commonly accepted that a successful accomplishment of assigned tasks requires some sort of real time capability to quickly react and adapt to environmental changes, it is not clear which operating system support is best suited for the scheduling and synchronizing of concurrent activities with different timing requirements. This paper discusses this problem, comparing two different real time scheduling policies for autonomous robot applications: pre-emptive rate monotonic and non pre-emptive Earliest Deadline First (EDF). Experimental results are presented and evaluated. 相似文献
7.
在实时数据库及数据处理系统中,针对周期性实时事务,应用经典的EDF等调度算法对其可以得到可行的调度;而对于混合实时事务-事务的时间性质是混合的,经典EDF不太适用。文中扩展EDF为最早实时事务截止期优先-ERtTDF(EarliestReal-timeTransactionDeadlineFirst),它可以有效地调度混合事务。文中给出了其可调度条件和时间需求条件,并把时间需求条件扩展到时限小于周期以及引入资源共享控制等方面,最后给出了集成调度实时、非实时以及混合事务的系统框架。通过性能比较,可以得到ERtTDF算法处理上面事务模型时性能较经典EDF更优。 相似文献
8.
Scheduling aperiodic tasks in dynamic priority systems 总被引:18,自引:2,他引:16
In this paper we present five new on-line algorithms for servicing soft aperiodic requests in realtime systems, where a set of hard periodic tasks is scheduled using the Earliest Deadline First (EDF) algorithm. All the proposed solutions can achieve full processor utilization and enhance aperiodic responsiveness, still guaranteeing the execution of the periodic tasks. Operation of the algorithms, performance, schedulability analysis, and implementation complexity are discussed and compared with classical alternative solutions, such as background and polling service. Extensive simulations show that algorithms with contained run-time overhead present nearly optimal responsiveness.A valuable contribution of this work is to provide the real-time system designer with a wide range of practical solutions which allow to balance efficiency against implementation complexity. 相似文献
9.
基于 Linux的实时控制系统的调度算法研究 总被引:1,自引:0,他引:1
在实时系统中,实时调度算法是影响实时性能的关键因素。本文首先分析了当前基于Linux的内核实时支持的相关主流技术,说明了Linux在实时性支持上的现状和弱点,综合比较了各种解决方案的优缺点。以往对实时调度算法的研究着重于硬实时性的满足,本文基于具体应用的特殊性以及当前对实时调度研究的发展趋势,对共存于同一系统中的
的周期性实时任务和非周期性任务的混合调度问题做进一步的探讨,提出一种实时任务的层次调度算法,保证了带宽的利用,克服了传统混合调度算法处理器利用率受限制、系统开销较大和非周期部分响应时间长的问题。基于这些研究成果,提出了改造方案,并在Linux操作系统中予以了实现。 相似文献
的周期性实时任务和非周期性任务的混合调度问题做进一步的探讨,提出一种实时任务的层次调度算法,保证了带宽的利用,克服了传统混合调度算法处理器利用率受限制、系统开销较大和非周期部分响应时间长的问题。基于这些研究成果,提出了改造方案,并在Linux操作系统中予以了实现。 相似文献
10.
Improved multiprocessor global schedulability analysis 总被引:1,自引:0,他引:1
Sanjoy Baruah Vincenzo Bonifaci Alberto Marchetti-Spaccamela Sebastian Stiller 《Real-Time Systems》2010,46(1):3-24
A new technique was recently introduced by Bonifaci et al. for the analysis of real-time systems scheduled on multiprocessor
platforms by the global Earliest Deadline First (EDF) scheduling algorithm. In this paper, this technique is generalized so
that it is applicable to the schedulability analysis of real-time systems scheduled on multiprocessor platforms by any work-conserving
algorithm. The resulting analysis technique is applied to obtain a new sufficient global Deadline Monotonic (DM) schedulability
test. It is shown that this new test is quantitatively superior to pre-existing DM schedulability analysis tests; in addition,
the degree of its deviation from any hypothetical optimal scheduler (that may be clairvoyant) is quantitatively bounded. A new
global EDF schedulability test is also proposed here that builds on the results of Bonifaci et al. This new test is shown
to be less pessimistic and more widely applicable than the earlier result was, while retaining the strong theoretical properties
of the earlier result. 相似文献
11.
The purpose of this paper is to define a series of requirements and associated experiments called the Hartstone Uniprocessor Benchmark (HUB), to be used in testing the ability of a uniprocessor system to handle certain types of hard real-time applications. The benchmark model considers the real-time system as a set of periodic, aperiodic (sporadic), and synchronization (server) tasks. The tasks are characterized by their execution times (workloads), and deadlines. There are five series of experiments defined. They are, in order of increasing complexity, PH (Periodic Tasks, Harmonic Frequencies), PN (Periodic Tasks, Nonharmonic Frequencies), AH (Periodic Tasks with Aperiodic Processing), SH (Periodic Tasks with Synchronization), and SA (Periodic Tasks with Aperiodic Processing and Synchronization). The general stopping criteria of the experiments is defined as follows: Change one of the following four task set parameters: number of tasks, execution time(s), blocking time(s), or deadline(s) until a given task set is no longer schedulable, i.e., a deadline is missed. The derivation of the Hartstone experiments from one static scheduling algorithm (Rate Monotonic) and one dynamic scheduling algorithm (Earliest Deadline First) is presented. Because of its high-level application view of the underlying hardware and real-time system software the Hartstone experiments can be used for fast prototyping of real-time applications. Implementation of such benchmarks is useful in evaluating scheduling algorithms, scheduling protocols, and design paradigms, as well as evaluating real-time languages, the tasking system of compilers, real-time operating systems, and hardware configurations. 相似文献
12.
13.
J. Delacroix 《Real-Time Systems》1996,10(3):263-291
Earliest Deadline algorithm is today the most attractive real-time scheduling theory. However, should the processor experience a transient overload, Earliest Deadline scheduling can not directly ensure that almost the most important tasks of the application are guaranteed. Schedulability condition should be employed to detect transient overloads before they occur, so that these transient overloads can be handle in an appropriate way. We say that Earliest Deadline scheduling is then unstable. The Regisseur is a real-time scheduling controller which provides the stability property to the Earliest Deadline scheduler by the mean of an importance criterion and by the mean of such schedulability condition. In this paper, we first describe the Regisseur principles and the way it works. Then an example is given to point out its performances. 相似文献
14.
《Journal of Systems Architecture》2015,61(9):398-409
Dynamic scheduling techniques, and EDF (Earliest Deadline First) in particular, have demonstrated their ability to increase the schedulability of real time systems compared to fixed-priority scheduling. In distributed systems, the scheduling policies of the processing nodes tend to be the same as in stand-alone systems and, although few EDF networks exist, it is foreseen that dynamic scheduling will gradually develop into real-time networks. There are some response time analysis techniques for EDF scheduled distributed systems, mostly derived from the holistic analysis developed by Spuri. A major factor influencing the response time is the release jitter of each task, which is the maximum variation suffered by the release time of the task jobs. The convergence of the holistic analysis in the context of EDF distributed systems with shared resources had not been studied until now. There is a circular dependency between the task release jitter values, response times and the preemption level ceilings of shared resources. In this paper we present an extension of Spuri’s algorithm and we demonstrate that its iterative formulas are non-decreasing, even in the presence of shared resources. This result enables us to assert that the new algorithm converges towards a solution for the response times of the tasks and messages in a distributed system.1 相似文献
15.
目前的嵌入式实时操作系统存在着内核结构较为复杂、臃肿、稳定性不高、对硬实时应用支持不足等问题.针对这些问题,结合现有的操作系统内核理论及嵌入式实时系统的特殊需求,通过组件化的设计,将内核划分为核心态基本模块及用户态扩展模块,提供多种进程间通讯(IPC)方式,并引入独特的硬实时抢占式调度机制,设计出一种精炼、稳定的硬实时微内核.通过这种设计思路成功开发出了昊鹏(Hopen)操作系统新版内核,应用于最新的3G手机产品上,取得了非常好的效果. 相似文献
16.
17.
强实时环境下调度非周期任务的时限寻优方法 总被引:1,自引:0,他引:1
文章提出了强实时环境下调度弱时限非周期任务的时限寻优方法(DOA),该方法在保证周期任务和偶发性任务满足时限要求的前提下,使非周期任务的响应时间达到最优。它还可根据实时应用的需要对算法的执行性能和计算复杂度进行折衷调整。仿真实验表明,DOA与现有的动态调度算法相比,使非周期任务响应时间更短,同时它收敛快,额外开销小,计算复杂度低,实现方便,因此是强实时环境下对周期任务与非周期任务进行混合调度的一种较好的方法。 相似文献
18.
一种机载DSP系统主控机的实时计算模型 总被引:1,自引:0,他引:1
现代机载数字信号处理(DSP)系统中的主控机是具有严格实时需求的计算环境,负责实时存储,显示和控制等重要功能,针对机载DSP系统的特殊性及其对实时计算的具体需求,提出了一种基于实时Linux技术的实时计算模型,它通过与操作系统层的实时支持相结合,实现了包括多任务并发的实时调度方法,硬实时和软实时任务协同工作机制以及实时事件驱动机制在内的完整运行环境,相对于现有的基于分时操作系统的方案,实时性能更为可靠,计算资源利用率高,相对于使用受严格许可证限制的商业实时操作系统的技术,应用开发灵活易行,软件成本更低。 相似文献
19.
标准Linux对实时应用提供了有限的支持。为了改进Linux的实时性能,详细分析了目前Linux实时化的主要技术方法和研究进展,通过从内核抢占机制、中断控制、细化时钟粒度及实时调度策略几方面深入研究,实现了一种Linux内核实时方案。实验结果显示,所做改进以不大的代价有效地提高了Linux的实时性能。同时指出了方案的不足和今后的研究方向。 相似文献
20.
In this paper, we are concerned with the problem of serving soft aperiodic tasks on a uniprocessor system where periodic tasks are scheduled on a dynamic-priority, preemptive basis and exclusively access to critical sections. Scheduling of tasks is handled by the Dynamic Priority Ceiling Protocol working with an Earliest Deadline scheduler. Our analysis determines the maximum processing time which may be stolen from periodic tasks without jeopardizing both their timing constraints and resource consistency. It provides the basis for an on-line scheduling algorithm, the EDL Server, to deal with the minimization of response times for soft aperiodic tasks. 相似文献