Data Related Task Scheduling For Vehicular Ad Hoc Networks

The extensive application of multi-core system improves the parallelism of tasks,however,brings the extra cost of inter-core communication.There are a large number of tasks which are data related.For those tasks which are related to security,inter-core communication will significant affect the schedule length and real-time,and then threaten the safety of vehicles and people.Aiming at the problem of real-time task response in multi-core processor system,this paper proposes a data related task scheduling algorithm(DTSV)for Vehicular Ad Hoc Networks(VANETs),with considering the multi-task concurrency mechanism in VANETs.Firstly,based on the common data related task model and the task characteristics in vehicle networks,a related task model based on data correlation of vehicular networks applications is defined to describe the data relation of tasks in VANETs.Secondly,an evaluation function is proposed according to the related task model.The evaluation function is mainly constructed by the communicating tasks of computing task.And then a multidimensional vector is gotten from the evaluation function,to characterize the strong and weak correlation between tasks.Furthermore,a data related task scheduling algorithm based on the related task model and evaluation function is designed to reduce the inter-core communications during task execution by assigning tasks which have deep correlation in data into a same core.There are two phases for the algorithm,initialization phase and running phase.The initialization phase of the algorithm works at the start time of VANET system,to assign periodic tasks which generated at the start time.And the initialization phase can significantly reduce the schedule length of periodic tasks.The running phase of the algorithm can assign aperiodic tasks which generated at the running time.It can marginally improve the real-time of aperiodic tasks.The running time may cause the unbalanced load of the whole system,so a load balance strategy is proposed.The load balance strategy is base on data relation,which can reduce the increment of inter-core communication when a task is migrated.Finally,the experimental and simulation is conducted to compare DTSV with other multi-core task scheduling algorithm.According to the result of the experimental,DTSV can reduce the schedule length by 10.6%.It is a considerable optimization for tasks which are continuously executing.The response time of aperiodic tasks can be reduced by 33.5%averagely.The results of the experimental show that DTSV can effectively reduce the inter-core communication delay,shorten the task schedule length,reduce response time oftasks and improve the real-time of task response to data related periodic tasks and aperiodic tasks.Meanwhile,DTSV can maintain the load balance of the whole system when the load balance strategy is added.