A kernel-based solution for overload in mixed criticality multicore systems

Abstract

Mixing tasks of different criticality levels on the same processor has become common in modern embedded systems. Scheduling these complex systems on multicore processors is difficult, especially when targeting high utilization. The overload in mixed criticality systems is one of the important problems that faces system designers and may force them to lower the cores utilization to avoid this risky problem. If a fully utilized system is overloaded and no solution is applied, many of coming jobs will miss their deadlines and the system may stay overloaded all the time and never return back to its normal behavior. So, the overload must be transient and the system should guarantee that it can return back its normal behavior shortly after overload happens. In this paper, we present a kernel-based solution for the overload in mixed criticality systems using virtual time. A virtual timer delays the release time and deadlines of tasks in an overload state for a short time to guarantee that it can return back as quickly as possible to its normal behavior. The proposed solution avoids using any user space invocation, as it detects the overload and recovers from it completely inside the kernel space. Our experiments show that the time to recover from overload once it happens is decreased using our proposed technique.