Independence Thresholds: Balancing Tractability and Practicality in Soft Real-Time Stochastic Analysis
Independence Thresholds: Balancing Tractability and Practicality in Soft Real-Time Stochastic Analysis
复制标题
独立阈值：软实时随机分析中的易处理性和实用性之间的平衡
DOI：
10.1109/rtss.2014.38
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
James H. Anderson
中科院分区：
文献类型：
--
作者：
R. Liu;A. Mills;James H. Anderson
随机响应时间分析的问题被认为是在软实时多处理器并行处理器的背景下。为了使这种分析产生易处理的、封闭形式的结果，不可避免地需要假设执行时间是概率独立的。然而，在实际系统中，任务之间的随机依赖性往往是常见的。为了使封闭形式的分析结果被应用到这样的系统，独立阈值的概念被引入。这样的阈值是“可调的”每任务参数，其可以被调整以控制如在分析中假设的任务执行时间中的依赖性的程度，这样的阈值甚至可以应用于通过资源共享在任务之间存在显式依赖性的设置中。提出了一种用于设置独立阈值的方法，其中测量的任务执行时间进行已知的统计独立性测试。该方法被应用在一个案例研究涉及MPEG解码。在本案例研究中，与最坏情况下的配置相比，使用独立阈值可以将配置任务的执行时间减少3.5倍，而不会影响分析假设。
The issue of stochastic response-time analysis is considered in the context of soft real-time multiprocessor schedulers. For such analysis to yield tractable, closed-form results, it is inevitably necessary to assume that execution times are probabilistically independent. However, stochastic dependencies among tasks are often common in actual systems. To enable closed-form analysis results to be applied to such systems, the concept of an independence threshold is introduced. Such a threshold is a "tunable" per-task parameter that can be adjusted to control the extent of dependency in task execution times as assumed in analysis, such thresholds can even be applied in settings where explicit dependencies exist among tasks through resource sharing. A method is presented for setting independence thresholds in which measured task execution times are subjected to known statistical independence tests. This method is applied in a case study involving MPEG decoding. In this case study, the usage of independence thresholds enabled up to a 3.5-fold reduction in provisioned task execution times compared to a worst-case provisioning without compromising analysis assumptions.