Increasing resource utilization in mixed-criticality systems using a polymorphic VLIW processor

Mixed-criticality systems need to provide strict guarantees to hard real-time tasks and simultaneously, deliver high throughput for non-critical tasks. However, techniques to enhance performance more often than not affect the analyzability, e.g., caches, branch prediction, out-of-order (OoO) execution superscalar processing, and simultaneous multithreading (SMT). In this paper, we propose the use of a polymorphic VLIW processor to increase performance for non-critical tasks while maintaining analyzability. The processor achieves these goals by dynamically distributing computing resources (in the form of datapaths) to one or multiple threads. A static schedule guarantees the minimum amount of cycles to meet the deadlines for critical tasks. Datapaths that are not used by critical tasks can be assigned to non-critical tasks in a highly flexible way, thereby increasing resource utilization resulting in higher throughput. Our experiments show that our approach can exploit its dynamic properties to improve schedulability and assign up to 50% and on average 25% more resources to lower-priority threads during the execution of a static real-time schedule.