In one example, a system includes a flash memory, a Random-Access Memory (RAM), and a controller. The flash memory stores first and second initial overlays, where the first initial overlay includes a first overlay function and the second initial overlay includes a second overlay function. The controller copies the first initial overlay into the RAM based on the first overlay function being called, swaps the first initial overlay with the second initial overlay based on the second overlay function being called, and monitors functions calls between the first and second overlay functions over a monitoring period. The controller determines whether a number of the function calls is greater than a threshold value, and based at least in part on the number of function calls being greater than the threshold value, re-groups the first and second overlay functions into a new overlay, and stores the new overlay in the flash memory.