Hi Adi,
Adi Sudewa wrote:
>
> Hi,
>
> Suppose I have this procedure :
>
> void do_it()
> {
> complex_calculation();
> other_complex_calculation();
> }
>
> and this highest priority rtl thread(ignore syntax errors):
>
> pthread_make_periodic(PERIOD);
> while (1) {
> do_it();
> pthread_wait();
> }
>
> And my questions :
> (1) I assume if execution time do_it() is greater than PERIOD,
> then all the CPU time will be used by this thread and no other
> task have chance to run. Is it correct ?
Correct, and if persistent will hang and reboot the system.
> (2) How to measure the worst-case execution time of do_it() ?
> Can I just run it 100 times, do measurement, and pick the greatest
> value ?
>
Set the period to be much longer than expected (so you won't lock-up).
Take the time before and after do_it() and then calculate the worst
case. This can then be output with printk (every once in a while). If
you then run it, you can load the system and observe the results. To
know whether you got the absolute worst case is difficult, but you
should get a close idea of it from this test.
There are examples similiar to this in the RT distributions.
Regards, Stuart
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