A heuristic mixed real-time task allocation of virtual utilization in multi-core processor

Abstract

Multi-core processor is widely used as the running platform for safety-critical real-time systems such as spacecraft, and various types of real-time tasks are dynamically added at runtime. In order to improve the utilization of multi-core processors and ensure the real-time performance of the system, it is necessary to adopt a reasonable real-time task allocation method, but the existing methods are only for single-core processors or the performance is too low to be applicable. Aiming at the task allocation problem when mixed real-time tasks are dynamically added, we propose a heuristic mixed real-time task allocation algorithm of virtual utilization VU-WF (Virtual Utilization Worst Fit) in multi-core processor. First, a 4-tuple task model is established to describe the fixed-point task and the sporadic task in a unified manner. Then, a VDS (Virtual Deferral Server) for serving execution requests of fixed-point task is constructed and a schedulability test of the mixed task set is derived. Finally, combined with the analysis of VDS's capacity, VU-WF is proposed, which selects cores in ascending order of virtual utilization for the schedulability test. Experiments show that the overall performance of VU-WF is better than available algorithms, not only has a good schedulable ratio and load balancing but also has the lowest runtime overhead. In a 4-core processor, compared with available algorithms of the same schedulability ratio, the load balancing is improved by 73.9%, and the runtime overhead is reduced by 38.3%. In addition, we also develop a visual multi-core mixed task scheduling simulator RT-MCSS (open source) to facilitate the design and verification of multi-core scheduling for users. As the high performance, VU-WF can be widely used in resource-constrained and safety-critical real-time systems, such as spacecraft, self-driving cars, industrial robots, etc.