I am currently running Debian 9 stretch with a PREEMPT RT kernel patch on a beaglebone black. My kernel version is:
4.4.155-ti-rt-r155
I have performed a latency test by writing a kernel module that turn an LED on after an interrupt is triggered by a button push. The measured latency between the button push and the LED turning on is 330 microseconds. This is a bit strange since I expected a real time kernel to have a low latency (about 10-30 microseconds). Is there an extra step that I need to do to, perhaps in code, to get low latency?
Thank you.