Improving the accuracy vs. speed tradeoff for simulating shared-memory multiprocessors with ILP processors

Previous simulators for shared-memory architectures have imposed a large tradeoff between simulation accuracy and speed. Most such simulators model simple processors that do not exploit common instruction-level parallelism (ILP) features, consequently exhibiting large errors when used to model current systems. A few newer simulators model current ILP processors in detail, but we find them to be about ten times slower. We propose a new simulation technique, based on a novel adaptation of direct execution, that alleviates this accuracy vs. speed tradeoff. We compare the speed and accuracy of our new simulator, DirectRSIM, with three other simulators - RSIM (a detailed simulator for multiprocessors with ILP processors) and two representative simple-processor based simulators. Compared to RSIM, on average, DirectRSIM is 3.6 times faster and exhibits a relative error of only 1.3% in total execution time. Compared to the simple-processor based simulators, DirectRSIM is far superior in accuracy, and yet is only 2.7 times slower.