HarvOS: Efficient Code Instrumentation for Transiently-Powered Embedded Sensing

We present code instrumentation strategies to allow transientlypowered embedded sensing devices efficiently checkpoint the system's state before energy is exhausted. Our solution, called HARvOS, operates at compile-time with limited developer intervention based on the control-flow graph of a program, while adapting to varying levels of remaining energy and possible program executions at run-time. In addition, the underlying design rationale allows the system to spare the energy-intensive probing of the energy buffer whenever possible. Compared to existing approaches, our evaluation indicates that HARvOS allows transiently-powered devices to complete a given workload with 68% fewer checkpoints, on average. Moreover, our performance in the number of required checkpoints rests only 19% far from that of an “oracle” that represents an ideal solution, yet unfeasible in practice, that knows exactly the last point in time when to checkpoint.