MEDIATOR - A Mixed Criticality Deadline Honored Arbiter for Multi-core Real-time Systems

Abstract

Multi-core systems are the potential enablers of the overwhelming growth of mixed criticality systems. There exist challenges to the widespread usage of multi-core in mixed criticality systems due to the non-predictive resource access timings. In this work, we present a Last Level Cache (LLC) access control mechanism, MEDIATOR that guarantees high criticality job executions without deadline misses for multi-core mixed-criticality systems. In MEDIATOR, the LLC access requests of lower criticality jobs are honored, if and only if there exists adequate slack for higher criticality jobs. The legacy First-In, First-Out (FIFO) arbiter has high deadline miss probability for high criticality jobs. The MEDIATOR behaves differently from legacy arbiter only when slack of higher criticality jobs is less. It guarantees successful execution of higher criticality jobs by blocking low criticality jobs. The experimental evaluation with software simulation and hardware implementation confirms the successful completion of high criticality jobs with LLC contention by honoring low criticality jobs whenever possible. Simulation results with the help of synthetic benchmark suites show successful completion of high criticality jobs at a high workload where legacy arbiter fails. The hardware design synthesized in Cadence using Genus Synthesis Solution 17.21 shows that MEDIATOR takes negligibly small time and energy overhead to achieve the same.