Improving the performance and power efficiency of shared helpers in CMPs

Abstract

Technology scaling trends have forced designers to consider alternatives to deeply pipelining aggressive cores with large amounts of performance accelerating hardware. One alternative is a small, simple core that can be augmented with latency tolerant helpers. As the demands placed on the processor core varies between applications, and even between phases of an application, the benefit seen from any set of helpers will vary tremendously. If there is a single core, these auxiliary structures can be turned on and off dynamically to tune the energy/performance of the machine to the needs of the running application.As more of the processor is broken down into helpers, and additional cores are added to a single chip that can potentially share helpers, the decisions that are made about these structures become increasingly important. In this paper we describe the need for methods that effectively manage these helpers. Our counter-based approach can dynamically turn off three helpers on average while staying within 2% of the performance when running with all helpers. In a multicore environment, our intelligent and flexible sharing of helper provides an average 24% speedup compared to static sharing in conjoined cores. Furthermore we show a benefit from constructively sharing helpers among multiple cores running the same application.