Time-sensitivity-aware shared cache architecture for multi-core embedded systems

Abstract

In embedded systems such as automotive systems, multi-core processors are expected to improve performance and reduce manufacturing cost by integrating multiple functions on a single chip. However, inter-core interference in shared last-level cache (LLC) results in increased and unpredictable execution times for time-sensitive tasks (TSTs), which have (soft) timing constraints, thereby increasing the deadline miss rates of such systems. In this paper, we propose a time-sensitivity-aware dead block-based shared LLC architecture to mitigate these problems. First, a time-sensitivity indication bit is added to each cache block, which allows the proposed LLC architecture to be aware of instructions/data belonging to TSTs. Second, portions of the LLC space are allocated to general tasks without interfering with TSTs by developing a time-sensitivity-aware dead block-based cache partitioning technique. Third, to reduce the deadline miss rate of TSTs further, we propose a task matching in shared caches and a cache partitioning scheme that considers the memory access characteristics and the time-sensitivity of tasks (TATS). The TATS is combined with our proposed dead block-based scheme. Our evaluation shows that the proposed schemes reduce deadline miss rates of TSTs compared to conventional shared caches. On a dual-core system, compared to a baseline, equal partitioning, and state-of-the-art quality-of-service-aware cache partitioning, our proposed dead block-based cache partitioning provides 9.3%, 30.5%, and 2.6% lower average deadline miss rates, respectively. On a quad-core system, compared to the baseline, equal partitioning, and state-of-the-art quality-of-service-aware cache partitioning, the combination of our proposed schemes provides 21.2%, 17.7%, and 4.1% lower average deadline miss rates, respectively.