Research On Scheduling Algorithm Of Mixed Critical System Based On Virtual Computer

With the increasing complexity of embedded system functions and the improvement of computing performance,in order to break through the limitations of system hardware size,weight and power consumption,embedded system integrates subsystems of different critical levels on the same hardware platform.Due to the different importance of subsystems with different criticality levels to the whole system,the system running time robustness can't be guaranteed and the worst execution time estimation of different criticality levels tasks between the authenticator and the designer in the static authentication is contradictory.The research of mixed-critical system scheduling algorithm is mainly to solve the above problems.At present,the research of mixed-critical system scheduling algorithm on multiprocessor platform focuses on global scheduling algorithm and partition scheduling algorithm,but these two algorithms have some defects.In the final emulation stage,most of researches adopt the method of algorithm emulation,without considering the extra cost in the real operating system scheduling process.According to the research of existing mixed-critical system scheduling algorithm,this study designs a mixed-critical system semi-partition scheduling algorithm based on EDF-VD algorithm,which is suitable for multiprocessor platform.and proposes a division method of fixed tasks and migration tasks.Ignoring the scheduling overhead,using the algorithm emulation method,the designed semi-partition scheduling algorithm is compared with the global scheduling algorithm and partition scheduling algorithm of the mixed-critical system based on EDF-VD algorithm.Considering the scheduling overhead in the operating system,a semi-partition scheduling algorithm is implemented in the operating system by adding a new scheduler class to the Linux real-time kernel.Furthermore,based on QEMU,the virtual computer is set up,and on different virtual hardware platforms,the Linux real-time kernel which realizes the mixed-critical system semi-partition scheduling algorithm is loaded,and the verification platform of the mixed-critical system scheduling algorithm in the real environment is built.Finally,the mixed-critical task set is scheduled on the verification platform,and its task attributes and time parameters under different system criticality levels are tracked and recorded.Through the schedulability verification of the actual operating system,the difference ofthe schedulability of the designed semi-partition scheduling algorithm between different virtual hardware platforms is compared,and the comparison between the real operating system and the simulated scheduling results of the algorithm is given,and the scheduling cost of the semi-partition scheduling algorithm of the mixed-critical system in this study is calculated.The emulation results show that the semi-partition algorithm designed in this study has higher algorithm schedulability than the global scheduling algorithm and partition scheduling algorithm based on EDF-VD algorithm.The experimental results on the virtual computer verification platform show that the semi-partition scheduling algorithm is schedulable on different virtual hardware platforms after considering the scheduling overhead,and it is feasible to implement in the real operating system environment.