Minimizing Energy Consumption of Embedded Systems via Optimal Code Layout

Code repositioning is a well-known method of reducing inefficient off-chip memory accesses by streamlining cache behavior. Embedded systems with predetermined applications can achieve further improvement with the addition of fast and energy efficient scratchpad memory (SPM) on chip and moving frequent accesses code and/or data from main memory to SPM. While many researchers have attempted to either streamline cache accesses or improve the effectiveness of SPM, few studies focus on exploring their joint synergy. This study proposes integer linear programming (ILP) models that include both code repositioning and SPM code selection to identify the optimal code layout and reduce energy consumption in embedded systems with a cache and SPM. This study also proposes a two-stage metaheuristic algorithm. Experimental results reveal that 1) allocating a dedicated portion of the on-chip SRAM to the SPM is not always better than using a cache-only configuration and 2) it is not trivial to select code objects for the SPM. As much as 55 percent additional energy can be saved by applying both code repositioning and SPM code selection techniques.