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I have to set up RTLinux and run a real-time ST language interpreter. The official RTLinux has been abandoned and its official download site does not work. I decided to use community RT_PREEMPT patch. How to configure it to achieve the most accurate timing?

I'm currently using Debian Wheezy on NP-R540-JS01PL notebook. I downloaded 3.18.9 kernel and 3.18.9-rt5 patch. I copied /boot/.config to source directory as mentioned on Wiki and changed preemt mode to fully preemtive kernel. Which other options do I need to change?

Will I get accurate results when I just replace old Debian kernel with the patched kernel? Notice that I'm running full Debian Wheezy with XFCE desktop environment.

Another option is to create a separate Linux distro only with patched kernel and basic command-line tools. How about drivers and kernel modules? My CPU has virtualization support. If I set up RTLinux on VirtualBox on Win7 or Debian Squeezy, will virtualized RTLinux still behave realtime?

Note that ST language interpreter will communicate with another application or service that will load ST code into the machine, read/write memory, blink LEDs, set time, parameters, etc.

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I have compiled the preempt Linux kernel a number of times and IMHO, you are better off trying to compile an older version of the kernel like 3.4 than 3.18.

That being said, you are on the right track. You need to download the kernel and the patch. Patch the downloaded kernel, set the desired settings, compile and install. Detailed settings and howto are available on this page: http://www.osadl.org/Realtime-Preempt-Kernel.kernel-rt.0.html. You may then reboot into the real-time kernel if all goes well. You can not just replace your kernel with a real-time one manually.

Lastly, although I have not tried running preempt kernel in a virtual machine, IMHO it is not going to be a hard real-time system in the end then because if the communication to the external application is through the host OS then the host OS priorities would affect the performance of the overall system.

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