System interconnect extensions for fully transparent demand paging in low-cost MMU-less embedded systems

MMU-less embedded systems are the state of the art solution for deeply embedded computing environments. Thanks to the rapid evolution of such devices, nowadays applications that run on top of them are evolving from simple control tasks to more complex applications that involve an Operating System (OS). At the same time, cost budget remains unchanged in spite of the growing performance requirements. For this reason, traditional code loading and execution techniques like full code shadowing or execute-in-place may lead to a performance bottleneck. Even demand paging strategies lack consensus due to the customization and the complexity of the software infrastructure dealing with the memory management. The objective of this work is to implement a transparent hardware-based demand paging strategy for code loading and execution, targeting MMU-less embedded systems. This approach consists of making the system interconnect aware of the memory map, without burdening on the legacy OS code, application code and on the compilation framework. This approach materializes lower boot-up latency and shorter application execution time with respect to traditional loading and executing schemes.