Multiple PRM-Based Lockstep/Performance Mode Switches for Critical/Non-Critical Real-Time Tasks

Due to the complex computation requirements of autonomous car functions, high-performance ECUs are inevitable for the future automotive system architecture. However, it has been reported that high-performance ECUs are usually more susceptible to the soft-error due to the technology scaling. One of the key methods to tolerate these soft errors (i.e. transient faults) is the lockstep mechanism based on the hardware redundancy. However, since this uses multiple redundant cores to execute a single program, it is very inefficient in terms of resource usage. To cope with this drawback, a new feature, `Lockstep/Performance mode switch' was introduced. It aims to guarantee safety for safety-critical tasks using the lockstep and maximize throughput for non-critical tasks using different cores for different tasks. This paper proposes a real-time scheduling method in order to efficiently use this new feature following the previous work. We first propose a condition of Periodic Resource Model(PRM) that avoids pessimism while we construct a PRM with the harmonic task set. Then, we partition the given input set into multiple PRMs where each PRM possesses a harmonic task set and has the optimal PRM period and budget. Consequently, The proposed method achieves optimal maximum schedulable utilization, which is more resource-efficient than the previous work.