Online model swapping for architectural simulation

ABSTRACTAs systems and applications grow more complex, detailed computer architecture simulation takes an ever increasing amount of time. Longer simulation times result in slower design iterations which then force architects to use simpler models, such as spreadsheets, when they want to iterate quickly on a design. Simple models are not easy to work with though, as architects must rely on intuition to choose representative models, and the path from the simple models to a detailed hardware simulation is not always clear. In this work, we present a method of bridging the gap between simple and detailed simulation by monitoring simulation behavior online and automatically swapping out detailed models with simpler statistical approximations. We demonstrate the potential of our methodology by implementing it in the open-source simulator SVE-Cachesim to swap out the level one data cache (L1D) within a memory hierarchy. This proof of concept demonstrates that our technique can train simple models to match real program behavior in the L1D and can swap them in without destructive side-effects for the performance of downstream models. Our models introduce only 8% error in the overall cycle count, while being used for over 90% of the simulation and using models that require two to eight times less computation per cache access.