Achieving Stagnation-Free Intermittent Computation with Boundary-Free Adaptive Execution

This paper presents ELASTIN, a stagnation-free intermittent computing system for energy-harvesting devices that ensures forward progress in the presence of frequent power outages without partitioning program into recoverable regions or tasks. ELASTIN leverages both timer-based checkpointing of volatile registers and copy-on-write mappings of nonvolatile memory pages to restore them in the wake of power failure. During each checkpoint interval, ELASTIN tracks memory writes on a per-page basis and backs up the original page using custom software-controlled memory protection without MMU or TLB. When a new interval starts at each timer expiration, ELASTIN clears the write permission of all the pages written during the previous interval and checkpoints all registers including a program counter as a recovery point. In particular, ELASTIN dynamically reconfigures both the checkpoint interval and the page size to achieve stagnation-free intermittent computation and maximize forward progress across power outages. The experiments on TI's MSP430 board with energy harvesting traces show that ELASTIN outperforms the state-of-the-art scheme by 3.5X on average (up to orders of magnitude speedup) and guarantees forward progress.