The Research On Real-time Customization And Improvement Of Operating System For EAST PCS

The Plasma Control System(PCS)is based on x86 Linux servers,and its operating system's real-time performance has significant influence upon plasma control.The PCS has been updated from cluster version to single-node version,the Myrinet network between nodes is replaced by faster shared memory,so that the control cycle is possible to be shortened to 50?s.With the update of the PCS,kernel verison has to be updated to 2.6.32 or newer,this means the former real-time improvement method of masking interrupts has a limited effect on the new kernel.Besides,a shortened cycle of 50?s make it hard for the control processes to finish their job within the cycle when the system has an insufficient performance of real-time.So,it is necessary to customize the OS for a better real-time performance.Because the control processes run in polling loop mode,OS noise is the main cause of a bad real-time performance of the control processes.OS noise often comes from scheduling and interrupts,and it brings latency to the control processes.So,the PCS chooses 3.10 kernel in which LOC interrupts happen in lower frequency.The sources of OS noise are complicated,but there is no efficient analysis tool.So,an OS noise profiler is developed to do the analysis work,it is able to help user obtain the source and the influence of major OS noise.It is common to do some simple adjustments for the OS,and to set RT priority for processes to obtain better real-time performance.But those simple adjustments are not enough to ensure the real-time performance the PCS need.Besides,RT priority will cause the control processes blocked.With the help of the OS noise profiler,this paper gives a more comprehensive list of OS adjustments,and a configuration tool is developed.Besides,a kernel module is developed to solve the problem of multiple RT polling processes cannot run at the same time.Finally,by modifying the kernel code,a kernel parameter is offered to set the LOC interrupt frequency to a lower level.A split test is conducted,after testing for 1000s,there are just 2 delays above 1?s in a single process,and the worst delay is 2?s.The result proves that the customization methods for the OS are able to ensure PCS with sufficient real-time performance.