Beaglebone RT test


I use beaglebone black and install Linux Debian (Linux beaglebone 4.4.6-bone-rt-r6 #1 PREEMPT RT Thu Mar 17 04:47:32 UTC 2016 armv7l GNU/Linux), I want to test the characteristic of Real Time, so I use cyclictest:

After “cyclictest -p 90 - m -c 0 -i 200 -n -h 100 -q -l 10000”, I got:

# Total: 000010000
# Min Latencies: 00012
# Avg Latencies: 00032
# Max Latencies: 00053
# Histogram Overflows: 00000
# Histogram Overflow at cycle number:
# Thread 0:

The result means the average latencies is 32 us.

I wonder if it is normal or not? (In my opinion, it is a little wired, because with the RT-preempt patch, it should be better than it.)

And if there is something wrong in the process, please tell me .

Thanks so much.

I would say that avg latency of 32uS is very good and I would be skeptical of this result. I don’t know what cyclictest does, but I’m wondering what the CPU load is during this test. My guess is the CPU load is low and that is why you are getting 32uS. If the CPU load was high, I would expect the number to increase to 100uS or more. Even Xenomai, which has a dual kernel is only able to achieve 40uS under load.


Hi John,

Thanks so much for your response, as you said, it is true that there is no load for the CPU. It is well of getting this result, thanks again.



在 2016年3月31日星期四 UTC+8下午2:49:24,john3909写道:

u want real time behaviour use the pru !