Freezer: A Specialized NVM Backup Controller for Intermittently-Powered Systems

TL;DR

This paper introduces Freezer, a specialized NVM backup controller for intermittently-powered IoT systems that efficiently saves and restores state during power failures, significantly reducing backup size and time with minimal overhead.

Contribution

The paper presents a novel backup controller that dynamically tracks memory accesses and commits changes to NVM, eliminating the need for complex hybrid memories and enabling efficient state preservation.

Findings

8x reduction in backup size on benchmarks

100x faster backup time compared to traditional methods

Minimal area and power overhead of 0.4% and 0.8%

Abstract

The explosion of IoT and wearable devices determined a rising attention towards energy harvesting as source for powering these systems. In this context, many applications cannot afford the presence of a battery because of size, weight and cost issues. Therefore, due to the intermittent nature of ambient energy sources, these systems must be able to save and restore their state, in order to guarantee progress across power interruptions. In this work, we propose a specialized backup/restore controller that dynamically tracks the memory accesses during the execution of the program. The controller then commits the changes to a snapshot in a Non-Volatile Memory (NVM) when a power failure is detected. Our approach does not require complex hybrid memories and can be implemented with standard components. % and integrated in any MCU with Results on a set of benchmarks show an average $8\times$ reduction in backup size. Thanks to our dedicated controller, the backup time is further reduced by more than $100\times$, with an area and power overhead of only 0.4\% and 0.8\%, respectively, w.r.t. a low-end IoT node.