I'm doing a study to compare the linux default kernel with the kernel patched with preempt_rt. I used a lot of tools (stress-ng, T-Sui, CPU burn, cycletest) to check the effectiveness of the patch. But I can see that the default kernel does already provide a method to change the tasks priority to a "real-time-task". Therefore, all of the stress-tests show a similar result: my application is always performed as real-time task without any strong delays or something different surprising...
I know some differences that preempt_rt causes (like interrupts moved to thread context, less non-preemtive code in kernel) but how do I test them?? I've seen that the normal stress-tools show almost no impact on my real-time-application... Is there any tool to execute a kind of "high-non-preemtive-kernel-code" or that triggers a huge amount of interrupts?