Case study: Performance and WCET analysis for parallelised avionic applications with ODC2

In a hard Real-Time (HRT) domain such as avionics, the high application performance is as important as delivering a predictable execution time. More precisely, the performance is defined by the application Worst-Case Execution Time (WCET). A common practice to boost the application performance in general purpose computing is by parallelisation and parallel execution on a shared memory multicore processor. Hence, local caches, used for bridging the long memory latency, need to allow coherent accesses to shared data. Conventional cache coherence protocols impede a suitable timing analysis because of multiple reasons. In this paper, we introduce an avionics case study to analyse the applicability of the earlier proposed On-Demand Coherent Cache (ODC²). We experiment with a 3D Path Planning (3DPP) application executed on a multicore processor. By varying the number of cores and the level of application parallelism, we compare and analyse observed average case execution times (ACET) of the 3DPP application with ODC², Uncached (bypassing the cache for shared data), and Cache Flush (software-triggered cache invalidation) configurations. The ACET results of the 3DPP application suggest that ODC² significantly outperforms the Uncached configuration by 1.53 times and Cache Flush by 2.15 times. Furthermore, we study the WCET speedup of the 3DPP application by applying a static analysis OTAWA tool. In terms of worst-case performance, the ODC² achieves a speedup of 1.63 compared to Uncached and 3.17 compared to Cache Flush configurations.