high resolution timing in kernel?

Question

I'm writing a kernel module that requires function called in 0.1ms intervals measured with at least 0.01ms precision. 250MHz ARM CPU, the HZ variable (jiffies per second) is 100 so anything jiffies-based is a no-go unless I can increase jiffies granularity.

Any suggestions where/how to look?

Answer 1

Assuming the kernel you are running has the Hi-Res timer support turned on (it is a build time config option) and that you have a proper timer hardware which can provide the needed support to raise an interrupt in such granularity, you can use the in kernel hrtimer API to register a timer with your requirement.

Here is the hrtimer documentation: http://www.mjmwired.net/kernel/Documentation/timers/hrtimers.txt

Bare in mind though, that for truly getting uninterrupted responses on such a scale you most probably also need to apply and configure the Linux RT (aka PREEMPT_RT) patches.

You can read more here: http://elinux.org/Real_Time