Adaptation Strategies in Multiprocessors System on Chip

Multi-processor System-on-Chips (MPSoCs) have become increasingly popular over the past decade. They permit balancing performance and flexibility, the latter being a key feature that makes possible reusing the same silicon across several product lines or even generations. This popularity makes highlight on new challenges to deal with the increasing complexity of such systems. Programmability issues, for example, are considered with a lot of attention, as those architectures allow new dimensions in design exploration. In this context, the development of adaptable mechanisms permits the optimization of the system behavior. This chapter explors three different adaptable mechanisms, and shows their benefits : frequency scaling, task migration techniques and memory organization. The modification of the frequency of each processor of a multi-core system allows fine tuning of power consumption under a varying process workload. Task migration permits balancing load among the several processors the system is made of. Our long-term vision of future embedded devices lies in adaptive systems made of thousands of processors in which tasks frequently migrate in response to the system state that is continuously monitored. Memory organization is a crucial criterion in MPSoC performance optimization, as memory access latency of remote data increases exponentially with respect to the number of cores. The computation-based programming model commonly used in single-core or few-cores based systems are no more suitable, and a transaction-based model are necessary to reach performances needs of new multimedia application.