对EAST PCS系统延迟的分析与改善

Analysis and Reduction of OS Latency in EAST PCS

在等离子体控制系统PCS中,操作系统噪声通常带来几微秒到几十微秒延迟,无法满足日益严格的控制要求.基于Linux内核机制,可推断延迟的产生主要由于调度和中断.为避免调度,对控制进程采用实时调度,并进行配套系统调整;为减少中断,进行中断迁移,并使用修改了内核滴答频率的Linux内核.最终延迟情况得到有效改善,从而为数据采集、计算和传输保留了充裕时间.

Inside the Plasma Control System（PCS）, Operating System（OS） noises usually bring latency measured in microseconds, which make the PCS hard to satisfy the increasing complexity of advanced plasma control requirements.Analysis shows that schedule and interrupts are the main cause of latency. In order to avoid scheduling, real-time priorities are applied in control processes, and related system adjustments are done. In order to decrease the frequency of interrupts, device interrupts are migrated and a revised kernel with fewer ticks is adopted. These work turn out to be efficient to reduce latency, and sufficient time is reserved for data acquisition, computation, and transmission.