Abstract-The current industry trend is towards using Commercially available Off-The-Shelf (COTS) based multicores for developing realtime embedded systems, as opposed to the usage of custom-made hardware. In typical implementation of such COTS-based multicores, multiple cores access the main memory via a shared bus. This often leads to contention on this shared channel, which results in an increase of the response time of the tasks. Analyzing this increased response time, considering the contention on the shared bus, is challenging on COTS-based systems mainly because bus arbitration protocols are often undocumented and the exact instants at which the shared bus is accessed by tasks are not explicitly controlled by the operating system scheduler; they are instead a result of cache misses. This paper makes three contributions towards analyzing tasks scheduled on COTS-based multicores. Firstly, we describe a method to model the memory access patterns of a task. Secondly, we apply this model to analyze the worstcase response time for a set of tasks. Although the required parameters to obtain the request profile can be obtained by static analysis, we provide an alternative method to experimentally obtain them by using performance monitoring counters (PMCs). We also compare our work against an existing approach and show that our approach outperforms it by providing tighter upper-bound on the number of bus requests generated by a task.
Shortcomings of this method, which lead to increased pessimism, are identified and addressed in the work of REF , which by following a similar approach, provides tighter bounds on the worst-case delays that a task may experience due to interference on the shared bus to the memory.
Response Time Analysis of COTS-Based Multicores Considering the Contention on the Shared Memory Bus
2011IEEE 10th International Conference on Trust, Security and Privacy in Computing and Communications
2011IEEE 10th International Conference on Trust, Security and Privacy in Computing and Communications
Computer Science