Memory reference reuse latency: Accelerated warmup for sampled microarchitecture simulation

This paper proposes to speedup sampled microprocessor simulations by reducing warmup times without sacrificing simulation accuracy. It exploiting the observation that of the memory references that precede a sample cluster, references that occur nearest to the cluster are more likely to be germane to the execution of the cluster itself. Hence, while modeling all cache and branch predictor interactions that precede a sample cluster would reliably establish their state, this is overkill and leads to long-running simulations. Instead, accurately establishing simulated cache and branch predictor state can be accomplished quickly by only modeling a subset of the memory references and control-flow instructions immediately preceding a sample cluster. Our technique measures memory reference reuse latencies (MRRLs) - the number of completed instructions between consecutive references to each unique memory location - and uses these data to choose a point prior to each cluster to engage cache hierarchy and branch predictor modeling. By starting cache and branch predictor modeling late in the pre-cluster instruction stream, we were able to reduce overall simulation running times by an average of 90.62% of the maximum potential speedup (accomplished by performing no pre-cluster warmup at all), while generating an average error in IPC of less than 1%, both relative to the IPC generated by warming up all pre-cluster cache and branch predictor interactions.