The National Science Foundation awarded Pennsylvania State University, University of Pittsburgh, and the University of Virginia (CACAO—Consortium for Adaptive CMP Compilation and Optimization) to investigate advanced runtime systems necessary to support multicore architectures. With the emergence of the multicore architecture comes the promise of integrating enormous computing power in a single chip, thereby enabling parallel computing in all types of platforms including handheld computers and desktop machines. Providing proper software support for applications is critical to harness the true power of this architecture. An inherent characteristic of multicores that presents a significant obstacle is runtime variation: reliability, energy/thermal behavior and process variation will vary across identically designed components of a multicore, producing a negative impact on application power consumption and performance. Runtime variation has been identified as one of the key problems that could block further scaling of circuits if not properly addressed.

As one focus of their efforts, the CACAO team is developing a system that dynamically mediates, controls and adapts an application’s execution to the runtime resource landscape originating from runtime variations. The system, called REEact (Robust Execution Environment) employs a combination of techniques in adapting both the hardware resources and the application software code to overcome the impact of runtime variations. At the hardware level, REEact adapts the resources, such as setting the speed/voltage of a node on the multicore. At the software level, it dynamically optimizes code, taking into account performance and power consumption due to runtime variations. It elicits the help of the OS in determining what resources to use in running the application. REEact informs the OS about information it dynamically discovers about latency, power, and application behavior. REEact is built as multi-layer hierarchical runtime system that interacts with the parallel application, the OS, and the underlying multicore architecture to ensure that maximum performance is achieved.