Optimizing AUTOSAR multicore distributions: Practical considerations for automotive software

The shift to multicore in automotive

The automotive industry is rapidly embracing multicore architectures to meet the growing demands of advanced functionalities and centralized vehicle architectures. Similar to the desktop computing revolution of the early 2000s, today's software systems must evolve to leverage the full potential of multicore microcontrollers (MCUs) and Systems-on-Chip (SoCs). This transition presents significant challenges, requiring developers to rethink their approach to software design, configuration, and optimization. ETAS, a leader in automotive software solutions, has been at the forefront of this evolution, developing the world’s first multicore AUTOSAR stack for vehicle series production back in 2009. With over 4 billion ECUs worldwide relying on ETAS RTA-CAR (RTA-Classic AUTOSAR), the company has gained extensive experience in helping automotive customers navigate the complexities of multicore implementations.

The challenges of parallelization and deeply embedded systems

Simply adding more cores doesn't automatically translate to linear performance gains. Factors like synchronization overhead, context switching, resource contention, memory access times, and the inherent limitations of Amdahl's Law all contribute to the challenge of achieving optimal parallelization. The key lies in maximizing parallel operations, minimizing sequential tasks, and optimizing memory usage to avoid bottlenecks.

Deeply embedded systems in vehicles have stringent requirements for safety, reliability, and real-time behavior. Historically, these systems have been built on single-core architectures. Migrating existing single-core code to multicore environments is difficult. Migrating existing legacy systems to multicore is often preferred over designing a new system from scratch. ETAS was among the first to introduce multicore support to the AUTOSAR standard and simultaneously developed the ETAS RTA-CAR BSW Stack to make the functionality usable. The RTA-CAR BSW stack has gradually been developed into a comprehensive stack portfolio, offering various architectural options for BSW distribution, including the 'master/satellite' pattern, designed to optimize core utilization in partitioned systems.

Practical Implementations: Real-world examples

This white paper explores practical considerations for optimizing AUTOSAR multicore distributions through real-life automotive examples. It examines three distinct scenarios:

• Optimizing load distribution: An OEM faced runtime issues on one core of their multicore ECU. ETAS helped redistribute the load by moving the Com stack from the overloaded core to a less burdened one. This resulted in a better distribution of the workload. It is crucial to understand the specific optimization goals to determine the best configuration for the system.

• Reducing runtime spikes: A Tier 1 supplier encountered performance bottlenecks during runtime spikes in a brake ECU. ETAS optimized the Com stack by splitting the Com_MainFunctionRx into multiple functions with different periods, aligning with the timing requirements of the Application Software (ASW). The split was done from layers close to the bus communication towards the ASW. It is beneficial to process the trigger in the bus stack, and let the higher layers poll the messages that should be sent or received.
• Master/Satellite and multi-master approach to BSW module distribution: AUTOSAR addresses the distribution of BSW modules across cores using the master/satellite pattern. Where the ASW needs to access a function in a different partition, the master controls the lower layers, and the satellites provide access for the ASW on other cores. ETAS also provides the multi-master approach. Using this approach, projects can map complete buses to other cores.
• Setting up an innovative multicore project from scratch: A customer tasked ETAS with designing a new generation of gateway ECUs with bus mirroring and a highly distributed Com stack. This greenfield scenario allowed for a tailored distribution across five cores, optimizing performance and implementing novel requirements within a challenging timeline. ETAS took a different approach to ensure data integrity. The implementation of the PduR interface via the proprietary ETAS RTA-CAR BSW module XCoreCDD (Cross-Core Complex Device Driver) no longer requires locks and can further optimize the process.

ETAS RTA-CAR: Empowering multicore automotive software development

ETAS RTA-CAR is a cutting-edge, low-footprint software solution designed for series production in automotive applications. Used by hundreds of companies worldwide, RTA-CAR powers billions of automotive ECUs in millions of vehicles. It is suitable for single and multicore projects. RTA-CAR offers solutions that goe beyond the AUTOSAR requirements.

These include:

• Lock-free XCoreCDD: implementation of a lock-free pipe that connects the PduR instances.
• Com adapter: decouples ASW distribution from Com stack distribution.
• Multi-master for WdgM: in addition to regular master/satellite, WdgM supports multi-master.

Looking ahead

Efficient multicore distribution is critical for next-generation vehicle architectures. ETAS is continually expanding the multicore capabilities of RTA-CAR, including tools to understand and optimize multicore performance. Upcoming releases will introduce new features and optimizations to further empower OEMs and Tier 1 suppliers to maximize the potential of current and future vehicle architectures. The new exclusive area configuration editor uses static analysis help users optimize their project.