基于双数据通路的快速上下文切换方法

Fast Context Switch Based on Dual Data Paths

嵌入式实时操作系统对时间性能有着严格的要求.上下文切换在实时操作系统中频繁发生,其时间开销直接影响整个系统的实时性能.针对一款拥有双数据通路、对存储系统具有并行访问能力的DSP系统,研究出一种快速上下文切换的方法.该方法将任务上下文相关的寄存器组分为两部分,分别保存在可以并行访问的内存中,通过DSP的双数据通路并行存取这两部分的内容.该方法在一款开放源代码的操作系统RTEMS中进行了验证,实验表明,在该DSP系统中,采用基于双数据通路的上下文切换方法能将上下文的保存和恢复时间降低为单数据通路的49.04%.

Time overhead is important in real-time operating system. Context switch is one major delay because it occurs frequently in a RTOS. The given DSP has features for having a dual data paths, providing multiple storage blocks can be accessed in parallel, general-purpose register banks can be accessed in parallel. To reduce the overhead of context switching, we proposed a solution based on the features of the given DSP. We split registers of context into two parts, and saved them in two memory parts which can be subjected to parallel access. When context switching, saving and restoring the registers of context via dual data paths is rather than one. This solution had been implemented in the RTEMS operating system. The experimental results show that saving and restoring the registers via dual data paths can reduce the processing time by 49.04% comparing to one data path.