RePage: A Novel Over-Air Reprogramming Approach Based on Paging Mechanism Applied in Fog Computing.

In fog computing, fog nodes running different tasks near the sources of data are required. Limited to on-board resource, fog node finds it hard to execute multiple tasks and needs over-air reprogramming to rearrange them. With respect to reprogramming, energy efficiency is one of the key issues for over-air reprogramming. Most of traditional reprogramming approaches focus on the energy efficiency during data transmission within network. However, program rebuilding on fog node is, as another significant energy cost, caused by writing/reading local high-power memory. We present a novel incremental reprogramming approach, RePage, in three stages. Firstly, we design a function paging mechanism that makes similar functions to one function page and caches them in low-power volatile memory to save energy. Secondly, we design new cache replacement algorithm for function page considering both modification times and range on the page. At last, further reducing writing/reading operations, we also redesign function invocation manner by centralized managing function addresses. Experiment results show that RePage reduces the sum of reading/writing operations on volatile memory by 89.1% and 92.5% compared to EasiCache and Tiny Module-link, and its hit rate is improved by 10.4% to Least Recently Used (LRU) algorithm.