C3: cooperative code positioning and cache locking for WCET minimization

Abstract

Worst-case execution time (WCET) is an important metric for designing real-time systems. Previous work such as code positioning and cache locking has been proposed for WCET reduction. Traditionally, these two techniques have been applied independently, which cannot derive desirably tight WCET. In this paper, a cooperative code positioning and static instruction cache locking (C3) framework is proposed to minimize WCET for real-time systems. We first propose the locking-basic-blocks selection heuristic to choose the most beneficial basic blocks on the longest path to improve WCET with locking. Then the code positioning technique is proposed to generate the memory layouts to reduce cache conflicts that influence WCET among these selected basic blocks or their functions. Based on the cache-locking-aware memory layouts, static cache locking is implemented to identify the most appropriate memory layout and also minimize WCET. The experiments show that compared to previous work, C3 reduces WCET significantly.