OPTIMIZING TIMED COSIMULATION BY HYBRID SYNCHRONIZATION

Abstract

In this paper, we present an approach to improving the performance of timed cosimulation. Our approach applies optimistic simulation concept to timed cosimulation for the reduction of synchronization overhead. It consists of (1) a predictive method for the synchronization between optimistic and synchronous simulators and (2) a method for the reduction of the state saving overhead inherent in optimistic simulation. To reduce the synchronization overhead, the predictive synchronization method predicts the time point when the next event is transferred between hardware and software. They the optimistic simulator runs optimistically until the predicted time point. Because of prediction and optimistic simulation, it is possible for the optimistic simulator to roll back and re-execute. To support rollbacks during optimistic simulation, states of the simulator are stored at checkpoints. In optimistic simulation, state saving can cause significant overhead in run-time and memory usage. For the reduction of state saving overhead, we perform state saving on a task basis, which enables saving only the state of currently running task without saving the whole state of the simulator at each checkpoint. Especially, single checkpoint property for hardware tasks enables minimizing the number of state savings in hardware simulation. We demonstrate the efficiency of the presented approach through cosimulation of two embedded system design examples.