Redundant Execution on Heterogeneous Multi-cores Utilizing Transactional Memory

Cycle-by-cycle lockstep execution as implemented by current embedded processors is unsuitable for energy-efficient heterogeneous multi-cores, because the different cores are not cycle synchronous. Furthermore, current and future safety-critical applications demand fail-operational execution, which requires mechanisms for error recovery. In this paper, we propose a loosely-coupled redundancy approach which combines an in-order with an out-of-order core and utilizes transactional memory for error recovery. The critical program is run in dual-modular redundancy on the out-of-order and the in-order core. The memory accesses of the out-of-order core are used to prefetch for the in-order core. The transactional memory system's checkpointing mechanism is leveraged to recover from errors. The resulting system runs up to 2.9 times faster than a lockstep system consisting of two in-order cores and consumes up to 35% less energy at the same performance than a lockstep system consisting of two out-of-order cores.