New Insights Into the Real-Time Performance of a Multicore Processor
Raimarius Delgado, Byoung Wook Choi
Abstract
Multicore processors are gaining popularity in various domains because of their potential for maximizing system throughput of average-case tasks. In real-time systems, where processes and tasks are governed by stringent temporal constraints, the worst-case timings should be considered, and migration to multicore processors leads to additional difficulties. Resource sharing between the cores introduces timing overheads, which affect the worst-case timings and schedulability of the entire system. In this article, we provide new insights into the performance of the real-time extensions of Linux, namely, Xenomai and RT-Preempt, for a homogeneous multicore processor. First, complete details on leveraging both real-time extensions are presented. We identify various multicore deployments and discuss their trade-offs, as established through the experimental evaluation of the scheduling latency. Then, we propose a statistical method based on a variation of chi-square test to determine the best multicore deployment. The unexpected effects of interfering loads, such as CPU, memory, and network operations, on the real-time performance, are considered. Feasibility of the best multicore deployment is verified through the analysis of its periodicity and deterministic response times in a pre-emptive multitasking environment. This research is the first of its kind and will serve as a useful guideline for developing real-time applications on multicore processors.