Linux real time performance

Hi, I’m testing the real-time performance of Linux. I have made an application with a thread. In the thread I wrote while(TRUE); and I have created a loop.

Playing with the priority I would have expected that when the thread is high priority the system frezee.
I run this command:
chrt -r -p 99 28803(pid my process)
With “top” I see my process It run with PR=rt and NI=-20.
I don’t understand why the system does not freeze.

I have done a other test with a GPIO and I see that when I move a window with the mouse the frequency of the GPIO changes. It seems like my task is not the highest priority. Why?

Thanks for the help.

I forgot in my linux image I have enabled rt extension.

You should definitely be able to starve user space when using the round robin (your case) or fifo scheduler. However, since you are using a dual core system (Colibri iMX6DL) I guess your system just uses the other CPU to run the rest of the tasks.

You’re right. I will do some tests using same applications on both cores.