Hi, Im working on an iMX6 based board with NXP kernel 4.1.15. I would like to understand why latency max returned by cyclictest increases from 20µs to 100µs when dohell accesses to USB.
Since i-pipe tracer refuses to work, I used ftrace to record cobalt, scheduling and irq events. Here is what I see on kernelshark: As expected, cyclictest has 1 xenomai thread per core (I can see them on /proc/xenomai/sched/threads) that wakes up periodically after a 200µs nanosleep. Sometimes, the wake up seems to be delayed (400µs instead of 200µs) because of an USB irq treatment followed by a call to usb-storage. Other times, the wake up seems to be delayed (400µs instead of 200µs) by a Linux call to ktimersoft, rcu and cat (see https://drive.google.com/file/d/18-B3WO2QH7PvBzJrt9tK5-TXvAkDxTPn/view?usp =sharing) Is it normal to delay a xenomai task wake up because of a Linux interrupt (I expected ipipe to act as a shield) ? How a simple Linux "cat" can delay a xenomai wake up ? Regards, Cédric. _______________________________________________ Xenomai mailing list Xenomai@xenomai.org https://xenomai.org/mailman/listinfo/xenomai
