Research And Implement Of Multi-Core Real-time Scheduling Algorithm For Mixed-Criticality System

With the continuous development of computer software and hardware technology,multi-core embedded real-time system is more and more widely used in all aspects of industry and life.In consideration of space,power and weight,the current mainstream trend is to integrate multiple tasks with different criticality levels which originally deployed in independent subsystems into a shared platform.This requires the real-time system to correctly schedule different criticality level tasks on the same platform,but the traditional real-time task scheduler can't meet this requirement.Driven by the actual demand,mixed-criticality system has increasingly become a research hotspot in the realtime field.The important goal of mixed-criticality system task scheduling algorithm is to ensure the time limit constraints of high-level critical tasks while improving the utilization of system resources.At present,the research on mixed-criticality system mainly focuses on theoretical simulation,and there is a little implementation in engineering field.Based on the mginkgo micro-kernel OS developed by UESTC,the thesis deeply analyzes the key technologies of real-time system,mixed-criticality system and multi-core processor,then designs and implements a multi-core real-time scheduler for mixed-criticality system.In this thesis,the hierarchical architecture is used to design the scheduler.The top layer is the global scheduling subsystem,which reasonably allocates the CPU core for tasks;The bottom layer is the local scheduling subsystem,which determines the execution order of tasks.This thesis generally includes the following functional modules:1.Task acceptance test module.The module is used to detect whether the task assigned to the core by the global scheduling subsystem can be scheduled with the tasks which accepted by the core.2.Slack stealer and temporal isolation mechanism.This mechanism is the key mechanism of the local scheduling subsystem,which realizes the temporal isolation between high-level critical tasks and low-level critical tasks and between the same critical tasks,so as to ensure that high-level critical tasks are not disturbed by low-level critical tasks.3.Task partition module.This module is the key function of the global scheduling subsystem.It focuses on the criticality levels of each task,assigns tasks to the CPU core which can be scheduled,and takes into account the needs of inter-CPU message optimization and load balancing.Besides,the original IPC communication mechanism of micro-kernel is optimized to meet the requirements of mixed-criticality system.It's mainly improved from 3 aspects:criticality level inversion avoidance,control flow switching acceleration and inter-CPU message optimization.Finally,the system is measured from the perspective of function and performance on the ARM-v7 a multi-core processor platform.The experimental results show that the scheduler designed in this thesis has good performance and meets the design expectation.