Departamento de Informática de Sistemas y Computadores

Abstract: The unpredictable behavior of conventional caches presents several problems when used in real-time multitask systems. It is difficult to know its effects in the Worst Case Execution Time and it introduces additional delays when different tasks compete for cache contents in multitask systems. This complexity in the analysis may be reduced using alternative architectures to cache memories, that improves predictability but obtaining similar performance. This is the case of locking caches, that may preload and lock cache contents, precluding the replacement during system operation, thus making cache and system behavior more predictable by means of simple, well-known and easy-to-use algorithms. This work presents an analysis of worst-case performance obtained with the static use of locking caches versus worst-case performance obtained with conventional (non-locking) caches. Analysis results show that predictability can be reached with no loss of performance, and the scenarios where the locking cache provides similar performance to conventional caches may be estimated from system parameters like task size, cache size, level of locality and level of interference, without running any experiment. Key-words: real-time systems, cache memories, locking cache, schedulability analysis, performance.