Summary
The term real-time is meaningless unless you qualify it with a deadline and an acceptable miss rate. When you have these two pieces of information, you can determine whether or not Linux is a suitable candidate for the operating system and, if so, begin to tune your system to meet the requirements. Tuning Linux and your application to handle real-time events means making it more deterministic so that the real-time threads can meet their deadlines reliably. Determinism usually comes at the price of total throughput, so a real-time system is not going to be able to process as much data as a non-real-time system.
It is not possible to provide mathematical proof that a complex operating system such as Linux will always meet a given deadline, so the only approach is through extensive testing using tools such as cyclictest and Ftrace and, more importantly, using your own benchmarks for your own application.
To improve determinism, you need to consider both the application and...
