Application-Specific Tailoring of Multi-Core SoCs for Real-Time Systems with Diverse Predictability Demands

Abstract

Embedded multi-core processors improve performance significantly and are desirable in many application-fields. This development, in particular, includes safety-critical real-time systems, which typically require a deterministic temporal behavior. However, even tasks without dependencies running on different cores can interfere due to, sometimes hidden, shared hardware resources, such as memory or communication buses. Consequently, only a pessimistic assumption of the worst-case execution time (WCET) that incorporates interference can be given. The desired performance gain therefore evaporates in the poor temporal analyzability. Safety-critical real-time systems are typically composed of multiple tasks with varying criticality levels and requirements on predictability and performance, respectively. In this paper, we present an approach that generates an application-specific, deterministic multi-core architecture for such mix-critical systems, thus eliminating the aforementioned hardware-induced interferences in the first place. Safety-critical tasks with stringent temporal requirements are mapped to dedicated Deterministic Execution Units (DEUs) while the remaining soft real-time tasks co-reside on a general purpose multi-core processor that offers performance over determinism. Just as well, predictable interconnections between DEUs are generated to satisfy dependencies and precedence constraints. Consequently, timing analysis for hard real-time tasks is significantly simplified, since interferences caused by shared resources and scheduling are finally eliminated. To show the benefits of our approach, an application-specific architecture for a flight controller was generated and compared to an ARM Cortex-A9 dual-core as a reference. Overall, we were able to significantly improve temporal properties of safety-critical tasks while preserving the overall performance for soft real-time tasks.