Scheduling with accurate communication delay model and scheduler implementation for multiprocessor system-on-chip

Abstract

In multiprocessor system-on-chip, tasks and communications should be scheduled carefully since their execution order affects the performance of the entire system. When we implement an MPSoC according to the scheduling result, we may find that the scheduling result is not correct or timing constraints are not met unless it takes into account the delays of MPSoC architecture. The unexpected scheduling results are mainly caused from inaccurate communication delays and or runtime scheduler's overhead. Due to the big complexity of scheduling problem, most previous work neglects the inter-processor communication, or just assumes a fixed delay proportional to the communication volume, without taking into consideration subtle effects like the communication congestion and synchronization delay, which may change dynamically throughout tasks execution. In this paper, we propose an accurate scheduling model of hardware/software communication architecture to improve timing accuracy by taking into account the effects of dynamic software synchronization and detailed hardware resource constraints such as communication congestion and buffer sharing. We also propose a method for runtime scheduler implementation and consider its performance overhead in scheduling. In particular, we introduce efficient hardware and software scheduler architectures. Furthermore, we address the issue of centralized implementation versus distributed implementation of the schedulers. We investigate the pros and cons of the two different scheduler implementations. Through experiments with significant demonstration examples, we show the effectiveness of the proposed approach.