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Rate-Monotonic Schedulability of Implicit-Deadline Tasks is NP-hard Beyond Liu and Layland’s Bound

机译:隐式截止日期任务的速率单调调度性是刘和莱德的束缚

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We study the computational complexity of the Fixed-Priority (FP) schedulability problem for sporadic or synchronous periodic tasks with implicit deadlines on a single preemptive processor. This problem is known to be (weakly) NP-complete in the general case, but Liu and Layland’s classic utilization bound trivially provides a polynomial-time solution for task sets with Rate-Monotonic (RM) priorities and utilization bounded from above by ln(2), or approximately 69%. Here we show that ln(2) is in fact the sharp boundary between computationally easy and hard schedulability testing: The FP-schedulability problem is NP-complete even if restricted to task sets with RM priorities and utilization bounded from above by any constant c > ln(2). This disproves a conjecture by Rothvoß. Further, we show that if a non-RM priority ordering can be specified, then the FP-schedulability problem is NP-complete already when utilization is bounded by any constant c> 0.
机译:我们研究了零星或同步周期性任务的固定优先级(FP)调度问题的计算复杂性,并在单个抢先处理器上具有隐式截止日期。已知这个问题是(弱)NP-TEMENT在一般情况下,但LIU和LATLAND的经典利用率介绍了速率 - 单调(RM)优先级的任务集的多项式解决方案,并且从LN界定的利用率( 2),或约69%。在这里,我们显示LN(2)实际上是计算简单和硬调度测试之间的尖锐边界:即使仅限于具有RM优先级的任务集和由上述任何常数C>限制的任务集,也是NP-Tressify的锐利边界。 ln(2)。这使Rothvoß掩盖了猜想。此外,我们表明,如果可以指定非RM优先级排序,则在使用任何常量C> 0时,FP-调度性问题已经是NP-Create。

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