Study On The IEEE 1588 Based Time Synchronization Technology Of Multi-task In Virtual Clusters

With the continuous improvement of computer systems and rapid development of the big data and cloud computing technology,the virtualization technology of hardware resources are widely used in distributed systems.When the virtual cluster performs distributed realtime application tasks,it is difficult to provide high precision time base for the execution of multiple real-time tasks,for clock drifts and synchronization performance degradations are more likely to occur due to the complexity of the virtual environment.In order to improve the time synchronization accuracy of a virtual cluster and realize the multi-task synchronization in distributed systems,we propose a hardware-based synchronization scheme and a software-based improvement scheme for different deployment environments and application requirements,providing a good and diverse solution for multi-task synchronization in virtual clusters.This project is based on IEEE 1588v2 protocol and KVM virtualization platform,exploring the hardware-assisted solution and pure software solution.(1)On the basis of the theory of virtual machine communication mechanism,we propose and implement a hardware-based synchronization scheme with good synchronization performance,which is mainly composed of IEEE 1588v2 hardware synchronization module and shared access to hardware module.The hardware network device of the slave clock is synchronized to the hardware network device of the master clock in the IEEE 1588v2 hardware synchronization module.The module is to tackle the problem that the use of the original driver only allows the host operating system or a guest operating system to monopolize the hardware device of the slave clock.In the user space of the virtual machine,by modifying the KVM module code in the kernel of the host computer,the hardware sharedaccess module completes the operation of accessing the hardware network device of the slave clock,acquiring the timestamp information of the hardware device and synchronizing the time of the guest operating system.(2)On the basis of the network I/O technology of Linux,combined with the idea of E2 E TC(End to End Transparent Clock)in IEEE 1588v2 protocol,we propose and implement a software-based improvement scheme with improved synchronization performance.The improvement is made to tackle the problem of delay asymmetry in the network I/O path of the host kernel by modifying the network communication code of the host kernel,calculating the residence time of the PTPv2 event message and accumulating it into the correction field in the message,achieving E2 E TC function for the host kernel.The PTPv2 synchronization software running on the guest user space can correct the total delay by these event messages to improve the accuracy of time synchronization.We build an experiment and test system to have a long time test on the synchronization scheme and its performance.In general,the synchronization accuracy and stability of the hardware-based synchronization scheme is higher than that of using the PTPd software by one order of magnitude,reaching microsecond level.The synchronization accuracy and stability of the software-based improvement scheme is about 50% higher than before,showing a significantly better synchronization performance.