| 摘要 | 为满足国内工控、嵌入式、多媒体等领域的需要,我们基于红旗Linux开发了RFRTOS实时操作系统.在该系统中,作者主要承担了如下三方面的工作：Linux的时钟粒度很粗糙（10ms）,难以满足实时应用的需求.RFRTOS改变了标准Linux时钟中断的固定频率模式,通过重新设定使得时钟得以微秒（μS）为单位在任何需要的时候产生中断,并提供了标准Linux核心时钟并行运行的一个细粒度的实时核心时钟处理系统.对于SMP的支持,我们设计并实现了由用户指定CPU的实时多处理器静态调度算法;CPU预留资源的主要变化是在系统初始化时,为每个CPU创建一个强制定时器.另外,在RFRTOS中,为了改进标准Linux核心不可抢占性和防止优先级反转,我们通过中断处理线程化、互斥锁机制的改进、每次中断返回都判断是否需要重新调度等方式实现了可抢占核心和对PIP协议的支持.目前,RFRTOS已经通过测试,并作为产品投入市场销售. |
| 其他摘要 | In real-time system, the correctness of the system depends not only on the logical result of the computation, but also on the time at which the results are produced. In hard real-time system, failure to meet deadline is considered to be a fatal fault. In soft real-time system, a few misses of soft deadlines do no serious harm, and only the system's overall performance becomes poorer and poorer when more and more jobs with soft deadlines complete late. Along with the development of compute sciences, embedded real-time system needs some services provided only in general OS. At the same time, some applications in the desktop environment also need real-time support. In order to support more sophisticated services in real-time OS, and satisfy the need of embedded system and processing control fields etc., we developed RFRTOS real-time OS based on Redflag Linux OS. In this system, I mainly undertake the following task: First, Linux's temporal granulariry is unacceptable for real-time system(lOms). Instead of using fixed rate timer interrupt, RFRTOS provides a microsecond resolution real-time timer queue running with standard Linux's timer queue concurrently. The test result shows that RFRTOS narrows timer deviation from 10ms to 30μ S (3/1000),while the overhead is less than 10μS. Second, although Linux supports SCHED_RR and SCHED_FIFO real-time scheduling policy according to POSIX standard, all these are insufficient for real-time system. In order to provide timely, guaranteed and enforced access to system resource, resouce reservation and other improved features are added in RFRTOS. As real-time scheduling test shows, a process always consumes CPU time as much as possible(C/T>>l) under stardard Linux. But in RFRTOS, the deviation of process run time is under 23 μS(include timer responsing and processing time, scheduling time etc.). Finally, RFRTOS supports static multiprocessor scheduling algorithm by which users specify a processor to execute their task. The main change in resource reservation is that an enforce-timer is created for every CPU. In addition, in order to resolve the non-preemptibility of Linux kernel and support PIP, we implement the IRQ thread, improve the spinlocks to mutex, and check for reschedule on return from every interrupt. Now, RFRTOS has passed the testing, and it has been put into market as a product. |
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