Hypervisor-Based Multicore Feedback Control of Mixed-Criticality Systems.

One of the most promising approaches to mixed-criticality systems is the use of multi-core execution platforms based on a hypervisor. Several successful EU Projects are based on this approach and have overcome some of the difficulties that this approach introduces. However, interference in COTS systems due to the use of shared resources in a computer is one of the unsolved problems. In this paper, we attempt to provide realistic solutions to this problem. This paper proposes a feedback control scheme implemented at hypervisor level and transparent to partitions (critical and non-critical). The control scheme defines two controller types. One type of controller is oriented towards limiting the use of shared resources by limiting bus accesses for non-critical cores. A second type measures the activity of a critical core and acts on non-critical cores when performance decreases. The hypervisor uses a performance monitor unit that provides event counters configured and handled by the hypervisor. This paper proposes two control strategies at hypervisor level that can guarantee the execution of critical partitions. Advantages and drawbacks of both strategies are discussed. Control theory requires to identify the process to be controlled. In consequence, the activities of the critical partitions must be identified in order to tune the controller. A methodology to deal with controller tuning is proposed. A set of experiments will show the impact of the controller parameters.