In Mixed-Criticality (MC) systems, although the high Worst-Case Execution Time (WCET) serves as a conservative upper bound representing the task's maximum execution time under all conditions, obtaining a low WCET is essential for representing realistic executions and improving utilization and Quality-of-Service (QoS). Nevertheless, determining appropriate low WCET(s) for lower-criticality (LO) modes poses a significant challenge. Opting for a very low value of this WCET enhances processor utilization by scheduling more tasks in LO mode. Conversely, employing a larger WCET ensures fewer mode switches, thereby enhancing QoS, albeit at the cost of processor utilization. This paper proposes an analytical approach, AnTi-MiCS, to determine the appropriate low WCET through design-time analysis of task executions. In some cases, a single low WCET may not be adequate to capture large variations in the execution time distribution, for example, in scenarios like bimodal distributions. Therefore, we further propose a scalable approach, MulTi-MiCS, to compute multiple appropriate low WCETs. This approach exploits the temporal correlation between subsequent inputs presented to the application. Experimental results, conducted on a real platform with embedded real-time benchmarks, demonstrate the efficacy of our proposed scheme, in which QoS is improved by 30.27% on average while reducing utilization waste by 35.89%, compared to existing approaches. Besides, MulTi-MiCS improves QoS by 6.41% compared to AnTi-MiCS while reducing utilization waste by 8.23%.

翻译：在混合关键系统中，尽管高最差执行时间（WCET）作为保守上界可表示任务在所有条件下的最大执行时间，但获取低WCET对于表征实际执行过程并提升系统利用率与服务质量（QoS）至关重要。然而，为低关键级（LO）模式确定合适的低WCET值仍面临重大挑战。若选择极低的WCET值，可通过在LO模式下调度更多任务来提升处理器利用率；反之，采用较大WCET值虽能减少模式切换次数以增强QoS，却会牺牲处理器利用率。本文提出分析框架AnTi-MiCS，通过对任务执行过程的设计时分析来确定合适的低WCET值。在某些场景（如双峰分布）中，单一低WCET值可能无法充分捕捉执行时间分布的剧烈变化，因此我们进一步提出可扩展方法MulTi-MiCS来计算多个合适的低WCET值。该方法利用应用连续输入之间的时间相关性。基于真实嵌入式实时基准测试平台的实验结果表明，与现有方法相比，所提方案平均可提升30.27%的QoS，同时降低35.89%的利用率浪费。此外，相较于AnTi-MiCS，MulTi-MiCS在降低8.23%利用率浪费的同时，进一步将QoS提升了6.41%。