WCET analysis in shared resources real-time systems with TDMA buses

Abstract

International audiencePredictability is an important aspect in real-time and safety-critical systems, where non-functional properties – such as the timing behavior – have high impact on the system cor-rectness. As many safety-critical systems have a growing performance demand, simple, but outdated architectures are not sufficient anymore. Instead, multi-core systems are more and more popular, even in the real-time domain. To combine the performance benefits of a multi-core architecture with the required predictability, Time Division Multiple Access (TDMA) buses are often advocated. In this paper, we are interested in accesses to shared resources in such environments. Our approach uses SMT (Satisfiability Modulo Theory) to encode the semantics and execution time of the analyzed program in an environment with shared resources. We use an SMT-solver to find a solution that corresponds to the execution path with correct semantics and maximal execution time. We propose to model a shared bus with TDMA arbitration policy. Using examples, we show how the WCET estimation is enhanced by combining the semantics and the shared bus analysis in SMT

Predictable Sharing of Last-level Cache Partitions for Multi-core Safety-critical Systems

“…Compared to [7], our analysis provides an exact (non-probabilistic) bound of a memory access in the LLC, and does not rely on MBPTA. Our work assumes that a TDM bus arbitration has one slot in each period, which is common in controlling access to resources in safety-critical systems [1,5]. We also identified the worst-case scenario for the LLC evictions, and that in the worst-case the latency can be unbounded if the arbitration has no constraint.…”

A Survey of Timing Verification Techniques for Multi-Core Real-Time Systems

“…In 2015, Rihani et al [103] used SAT Modulo Theory (SMT) to encode the whole execution of a task on a platform with TDMA bus arbitration. The novelty here is the encoding of the program semantics to gain precision in the WCET bound, taking infeasible execution paths into account.…”