UC Santa Cruz

Computer architects rely on simulators in order to explore their design space and evaluate innovations. However, the state-of-art cycle-accurate simulators are several orders of magnitude slower than the hardware they simulate. Long simulation times can result in a great decrease in productivity. We have developed LiveSim, a novel microarchitectural simulation methodology that provides simulation results within seconds, making it suitable for interactive use. LiveSim is able to report simulation results on the fly by incorporating a web interface. It is a scalable framework which efficiently takes advantage of resources to provide fast simulation results in an order of seconds.

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 random samples are gathered, LiveSim provides confidence intervals for the reported values and continues simulation until it reaches the target confidence level. We call simulation towards a target interval 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.