Modeling Contention Interference in Crossbar-based Systems via Sequence-Aware Pairing (SeAP)

Jeremy Giesen, Pedro Benedicte, Enrico Mezzetti, Jaume Abella, Francisco J. Cazorla

Abstract: The Infineon AURIX TriCore family of microcontrollers has consolidated as the reference multicore computing platform for safety-critical systems in the automotive domain. As a distinctive trait, AURIX microcontrollers are designed to promote high timing predictability as witnessed by the presence of large scratchpad memories and a crossbar interconnect. The latter has been introduced to reduce inter-core interference in accessing the memory system and peripherals. Nonetheless, the crossbar does not prevent requests from different cores to the same target resource to suffer contention. Applications are, therefore, inherently exposed to inter-core timing interference, which needs to be taken into account in the determination of reliable execution time bounds. In this paper we propose a contention modeling technique for crossbar-based systems, and hence suitable for bounding contention effects in the AURIX family. Unlike state of the art techniques that build on total request counts, we exploit the sequence of requests to the different target resources produced by each core to produce tighter bounds by discarding contention scenarios that cannot occur in practice. To that end, we adapt existing techniques from the pattern matching domain to derive the worst-case contention effects from the sequences of requests each core sends over the crossbar. Results on a wide set of synthetic and real scenarios and benchmark on an AURIX TC297TX show that our technique outperforms other contention modeling approaches.