IRQ Coloring and the Subtle Art of Mitigating Interrupt-Generated Interference

Integrating workloads with differing criticality levels presents a formidable challenge in achieving the stringent spatial and temporal isolation requirements imposed by safety-critical standards such as ISO26262. The shift towards high-performance multicore platforms has been posing increasing issues to the so-called mixed-criticality systems (MCS) due to the reciprocal interference created by consolidated subsystems vying for access to shared (microarchitectural) resources (e.g., caches, bus interconnect, memory controller). The research community has acknowledged all these challenges. Thus, several techniques, such as cache partitioning and memory throttling, have been proposed to mitigate such interference; however, these techniques have some drawbacks and limitations that impact performance, memory footprint, and availability. In this work, we look from a different perspective. Departing from the observation that safety-critical workloads are typically event- and thus interrupt-driven, we mask “colored” interrupts based on the Quality of Service (QoS) assessment, providing fine-grain control to mitigate interference on critical workloads without entirely suspending non-critical workloads. We propose the so-called IRQ coloring technique. We implement and evaluate the IRQ Coloring on a reference high-performance multicore platform, i.e., Xilinx ZCU102. Results demonstrate negligible performance overhead, i.e., < 1% for a 100 microseconds period, and reasonable throughput guarantees for medium-critical workloads. We argue that the IRQ coloring technique presents predictability and intermediate guarantees advantages compared to state-of-art mechanisms.