WCET-aware dynamic code management on scratchpads for Software-Managed Multicores

Software Managed Multicore (SMM) architectures have advantageous scalability, power efficiency, and predictability characteristics, making SMM particularly promising for real-time systems. In SMM architectures, each core can only access its scratchpad memory (SPM); any access to main memory is done explicitly by DMA instructions. As a consequence, dynamic code management techniques are essential for loading program code from the main memory to SPM. Current state-of-the-art dynamic code management techniques for SMM architectures are, however, optimized for average-case execution time, not worst-case execution time (WCET), which is vital for hard real-time systems. In this paper, we present two novel WCET-aware dynamic SPM code management techniques for SMM architectures. The first technique is optimal and based on integer linear programming (ILP), whereas the second technique is a heuristic that is suboptimal, but scalable. Experimental results with benchmarks from Mälardalen WCET suite and MiBench suite show that our ILP solution can reduce the WCET estimates up to 80% compared to previous techniques. Furthermore, our heuristic can, for most benchmarks, find the same optimal mappings within one second on a 2GHz dual core machine.