This paper is a very basic introduction on real-time concepts and on the state of real-time patches in the Linux kernel project. We start off with definition of real-time systems and some of the important metrics (Interrupt Latency, Scheduling Latency and Worst-case Latency) and explain each one of them with an analogy.
We also address some of the differences between real-time and general purpose operating systems which include analysis of several common misconceptions including performance issues, latency, hard vs. soft real-time systems, programming APIs and the software kernel.
We then step into the Linux kernel land discussing the current state of PREEMPT_RT patch and some of the other soft real-time features that are available in Linux kernel. Lastly we talk about improvements in latency effects with respect to kernel device drivers and the corresponding framework stack.
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