RETHROTTLE : Execution Throttling In The REDEFINE SoC Architecture

Abstract

REDEFINE is a reconfigurable SoC architecture that provides a unique platform for high performance and low power computing by exploiting the synergistic interaction between coarse grain dynamic dataflow model of computation (to expose abundant parallelism in the applications) and runtime composition of efficient compute structures (on the reconfigurable computation resources). Computer architectures based on the dynamic dataflow model of computation have to be an infinite resource implementation to be able to exploit all available parallelism in all applications. It is not feasible for any real architectural implementation. When limited resource implementations are considered, there is a possibility of loss of performance (inability to efficiently exploit available parallelism). In this thesis, we study the throttling of execution in the REDEFINE architecture to maximize the architecture efficiency. We have formulated it as a design space exploration problem at two levels i.e. architectural configurations and throttling schemes. Reduced feature/high level simulation or feature specific analytical approaches are very useful for the selective study/exploration of early in design phase architectures/systems. Our approach is similar to that of SEASAME Framework which is used for the study of MPSoC (Multiprocessor SoC) architectures. We have used abstraction (feature reduction) at the levels of architecture and model of computation to make the problem approachable and practically feasible. A feature specific fast hybrid (mixed level) simulation framework for the early in design phase study is developed and implemented for the huge design space exploration (1284 throttling schemes, 128 architectural configurations and 10 applications i.e. 1.6 million executions). We have done performance modeling in terms of selection of important performance criteria, ranking of the explored throttling schemes and investigation of the effectiveness of the design space exploration using statistical hypothesis testing. We found some interesting obvious/intuitive and some non-obvious/counterintuitive results. The two performance criteria namely Exec.T and Avg.TU were found sufficient to represent the performance and the resource usage characteristics of the architecture independent of the throttling schemes, the architectural configurations and the applications. The ranking of the throttling schemes based on the selected performance criteria is found to be statistically very significant. The intuitive throttling schemes span the range of performance from the best to the worst. We found absence of trade-off amongst all of the performance criteria. The best throttling schemes give appreciable overall performance (25%) and resource usage (37%) gains in the throttling unit simultaneously. The design space exploration of the throttling schemes is found to be fine and uniform.