Efficient realization of logical execution times in legacy embedded software

Abstract

The Logical Execution Time (LET) programming model has been recently employed as a parallel programming paradigm for multi-core platforms, in particular for porting large single-core applications to multi-core versions, which is a serious challenge faced in major industries, such as the automotive one. In this paper, we consider a transformation process from legacy single-core software to LET-based versions that are ready for multi-core, and focus on the problem of minimizing computational costs rooted in the additional buffering that is required to achieve the LET communication semantics, especially for parallel executions and in the presence of legacy event-driven functions that remain outside of the LET specifications. We propose a static analysis that proceeds top-down through successive layers of abstraction, where an optimal solution at a certain layer represents a minimal upper bound on the set of buffers determined in the next layer. We present a solution for the top layer, which is platform-independent and has no restrictions on executions of event-driven software. Furthermore, we derive optimal buffering for a second layer with a minimal platform configuration. We refer here to a three-layer implementation, which has been successfully applied to industrial automotive software, where further savings are achieved in the mapping from second layer buffers to memory locations. We also point to evaluation results, demonstrating the applicability of the approach in industrial settings.