共查询到19条相似文献,搜索用时 187 毫秒
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一种面向数控系统的动态反馈调度模型 总被引:1,自引:0,他引:1
由于数控系统的动态特性,其运行过程中可能会发生处理器过载现象.开环的调度算法无法在处理器过载时仍然保持系统的稳定,从而对加工精度造成影响.为了提高数控系统的稳定性,本文针对数控系统的混合任务集提出一个闭环的反馈调度模型.并通过实验对模型的有效性进行了验证.实验结果表明,该调度模型能够提高数控系统的稳定性. 相似文献
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通过对单调速率任务分配算法调度策略和可调度条件的分析,在多处理器周期任务抢占调度模型基础上,细致刻画了任务分配算法如何分配任务的行为。依据Liu和Layland定理,给出多处理器下任务分配算法的最小RM利用率界的定理。仿真结果表明,分配算法的利用率界是不同特征任务集选择不同分配算法进行任务划分的关键,通过对任务集总利用率与算法利用率界的比较,判断使用该算法对任务集是否可以产生可行分配。 相似文献
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分析了常见调度算法的特点,提出一种基于嵌入式实时操作系统的闭环反馈控制调度策略。针对任务的特点,从任务的周期与非周期性、I/O消耗和处理器消耗型两个方面对任务进行相应的反馈控制,使调度器具有一定程度上的自适应功能。并对实时操作系统μC/OS-II的内核调度算法进行改进,同时与EDF算法进行对比测试,可以看出改进后的调度算法在系统负载较重或系统过载的情况下表现良好。 相似文献
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在嵌入式实时操作系统中,由单个特征参数作为实时任务优先级的调度依据,并不能较好地描述系统中任务的关键性和紧迫性.提出一种基于组合优先级的自适应实时调度算法(SREDF),综合任务的截止期和CPU运行期设计任务的优先级,使截止期越早且CPU运行期越短的任务拥有最高优先级.处理器能有效地调度相同截止期的实时任务,并提前分析和预测任务能否完成.实验表明,该算法降低了任务调度的截止期错失率(MDP),并提高了任务调度的速度和效率. 相似文献
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分布式主动实时数据库基于多优先级队列的优先级分派 总被引:1,自引:0,他引:1
事务的分布性和事务触发的不可预测性使得分布式主动实时数据库系统中的事务调度变得较为复杂.该文给出了立即和推迟两种模式下执行的被触发事务的截止期确定方法和事务紧急度计算方法,并结合事务的应用语又提出了一种基于多优先级队列的优先级分派策略,有利于主动事务和被触发事务的顺利提交. 相似文献
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This paper discusses the stability of a feasible pre-run-time schedule for a transient overload introduced by processes re-execution during an error recovery action. It shows that the stability of a schedule strictly tuned to meet hard deadlines is very small, invalidating thus backward error recovery. However, the stability of the schedule always increases when a real-time process is considered as having a nominal and a hard deadline separated by a non-zero grace time. This is true for sets of processes having arbitrary precedence and exclusion constraints, and executed on a single or multiprocessor based architecture. Grace time is not just the key element for the realistic estimation of the timing constraints of real-time error processing techniques. It also allows backward error recovery to be included in very efficient pre-run-time scheduled systems when the conditions stated in this paper are satisfied. This is a very important conclusion, as it shows that fault-tolerant hard real-time systems do not have to be extremely expensive and complex. 相似文献
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M. G. Furugyan 《Programming and Computer Software》2014,40(1):21-27
The problem of preemptive scheduling in a real-time multiprocessor computing system with release time/deadline intervals is investigated. Approximate algorithms based on the generalization of a single-processor algorithm of relative priority are developed and compared to the exact maximum flow algorithm. An algorithm has been developed for the case where requests for the tasks occur periodically with given periods. An algorithm for determining the values of the processor performance for which there exists an admissible schedule for a given assembly of tasks with release time/deadline intervals has been developed. 相似文献
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考虑到生产力波动、现场条件改变等不确定性因素的影响,工程项目的进度管理一般采用计划评审技术(program evaluation and review technique,PERT)网络模型,并以未按期完工概率作为重要的进度风险分析指标.针对工程项目的未按期完工概率估算,基于区域分解法,提出一种新型的数值模拟算法.针对PERT网络中的任一路径,将该路径的工期超出目标工期的事件定义为基本事件,从而将项目的未按期完工事件表示为所有基本事件的并集.所提出算法通过估计基本事件间的交集程度,对基本事件的概率求和进行折减,从而估算项目的未按期完工概率.通过算例验证,所提出模拟算法具有较好的估算准确度,且与蒙特卡罗方法相比有明显的计算效率提升. 相似文献
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In a real-time system with both hard real-time periodic jobs and soft real-time aperiodic jobs, it is important to guarantee that the deadline of each periodic job is met, as well as to provide a fast response time for each aperiodic job. We propose an algorithm, called Proportional Slack Reserve (PSR), that produces an efficient schedule for such an environment. For every execution unit of a periodic job, the PSR algorithm reserves time which can be used for execution of aperiodic jobs. If reserved time is not available, the algorithm assigns a deadline to an aperiodic job for achieving better responsiveness of aperiodic jobs. The proposed algorithm can fully utilize processing power while meeting all deadlines of periodic jobs. It can also easily reclaim the time unused by the periodic job. We analytically show that for each aperiodic job, the response time in a PSR schedule is no longer than that in a TBS schedule, which is known to be efficient for servicing aperiodic jobs. We also present simulation results in which the response time of PSR is significantly improved over that of TBS, and moreover the performance of PSR compares favorably with TB(N) considering scheduling overhead. 相似文献