LACT: Liveness-Aware Checkpointing to reduce checkpoint overheads in intermittent systems

Intermittent computing supports execution of the systems experiencing frequent power failures, such as battery-less devices powered by energy-harvesting. In such systems, checkpoint and recovery is a commonly adopted technique, where volatile system states are regularly saved to Non-Volatile Memory (NVM), to preserve computing progress between power cycles. Since checkpoint involves a large number of NVM accesses, which is expensive in terms of both latency and energy, reducing its overhead has been a significant research challenge. In this paper, we present LACT (Liveness-Aware CheckpoinTing), a compiler optimization technique to minimize checkpoint overhead in intermittent systems. At the time of checkpoint execution, there exist dead values in general, which will not be used or overwritten in the future. LACT examines such liveness information, especially in arrays, based on compile-time analysis and excludes the dead values from the checkpoint to reduce required checkpoint data, which is a previously unexplored optimization opportunity. Our evaluation shows that LACT can reduce 46.4% of required checkpoint data without any runtime support, leading to reduction of 31.5% in execution time and a 5.2% decrease in power consumption on average. Our experiments in real energy-harvesting environment demonstrates that such improvement translates to a 31.6% improvement in end-to-end execution time.