Automatic workload synthesis for early design studies and performance model validation
Bell, Robert Henry
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Computer designers rely on simulation systems to assess the performance of their designs before the design is transferred to silicon and manufactured. Simulators are used in early design studies to obtain projections of performance and power over a large space of potential designs. Modern simulation systems can be four orders of magnitude slower than native hardware execution. At the same time, the numbers of applications and their dynamic instruction counts have expanded dramatically. In addition, simulation systems need to be validated against cycle-accurate models to ensure accurate performance projections. In prior work, long running applications are used for early design studies while hand-coded microbenchmarks are used for performance model validation. One proposed solution for early design studies is statistical simulation, in which statistics from the workload characterization of an executing application are used to create a synthetic instruction trace that is executed on a fast performance simulator. In prior work, workload statistics are collected as average behaviors based on instruction types. In the present research, statistics are collected at the granularity of the basic block. This improves the simulation accuracy of individual instructions. The basic block statistics form a statistical flow graph that provides a reduced representation of the application. The synthetic trace generated from a traversal of the flow graph is combined with memory access models, branching models and novel program synthesis techniques to automatically create executable code that is useful for performance model validation. Runtimes for the synthetic versions of the SPEC CPU, STREAM, TPC-C and Java applications are orders of magnitude faster than the runtimes of the original applications with performance and power dissipation correlating to within 2.4% and 6.4%, respectively, on average. The synthetic codes are portable to a variety of platforms, permitting validations between diverse models and hardware. Synthetic workload characteristics can easily be modified to model different or future workloads. The use of statistics abstracts proprietary code, encouraging code sharing between industry and academia. The significantly reduced execution times consolidate the traditionally disparate workloads used for early design studies and model validation.