LiveSim: Going live with microarchitecture simulation

Computer architects rely heavily on software-based microarchitecture simulators, which typically take hours or days to produce results. We have developed LiveSim, a novel microarchitectural simulation methodology that provides simulation results within seconds, making it suitable for interactive use. LiveSim works by creating in-memory checkpoints of application state, and then executing randomly selected samples from these checkpoints in parallel to produce simulation results. The initial results, which we call LiveSample, are reported less than one second after starting the simulation. As more samples are simulated the results become more accurate and are updated in real-time. Once enough samples are gathered, LiveSim provides confidence intervals for the reported values and continues simulation until it reaches the target confidence level, which we call LiveCI. We evaluated LiveSim using SPEC CPU 2006 benchmarks and found that within 5 seconds after starting simulation, LiveSample results reached an average error of 3.51% compared to full simulation, and the LiveCI results were available within 41 seconds on average.