Abstract -Cache memories have been introduced into embedded systems to prevent memory access times from becoming an unacceptable performance bottleneck. Memory and cache are split into blocks containing instructions and data. During a pre-emption, blocks from the pre-empting task can evict those of the pre-empted task. When the pre-empted task is resumed, if it then has to re-load the evicited blocks, cache related pre-emption delays (CRPD) are introduced which then affect schedulability of the task. In this paper, we show how existing approaches for calculating CRPD for FP scheduling can be adapted and integrated into schedulability analysis for EDF. We then compare the performance of the different approaches against an existing approach for calculating CRPD for EDF. Using a case study and empirical evaluation, we show the benefits of our CRPD analysis. Over the past 20 years, processor speeds have increased dramatically leaving memory access times as a major performance bottle-neck. To bridge this ever increasing gap, caches have been introduced between the processor and memory; however, they introduce significant complexity when trying to verify the timing properties of the system. Real-time systems, especially hard real-time systems, have very stringent timing requirements and the schedulability of each task must be known. The schedulability of a taskset is determined using information about the scheduling algorithm, the arrival pattern of tasks and the tasks' worst-case execution time. Worst-case execution times are typically obtained assuming no pre-emption. However, in pre-emptive multitasking systems, caches introduce additional cache related pre-emption delays (CRPD) caused by the need to re-fetch blocks belonging to the pre-empted task which were evicted from cache by the pre-empting task. These CRPD effectively increase the worst-case execution time of the tasks. It is therefore important to be able to calculate, and therefore account for, CRPD when determining if a system is schedulable or not. The motivation for this work comes from the need to provide accurate schedulability analysis for applications running on processors with cache, scheduled under EDF.
REF adapted a number of approaches for calculating CRPD for FP to work with EDF.
Integrating cache related pre-emption delay analysis into EDF scheduling
2013 IEEE 19th Real-Time and Embedded Technology and Applications Symposium (RTAS)
2013 IEEE 19th Real-Time and Embedded Technology and Applications Symposium (RTAS)
Computer Science