On 2011-05-27 21:11, Gilles Chanteperdrix wrote: > On 05/27/2011 08:29 PM, Jonas Witt wrote: >> Sorry, I missed the NTP-part. I am not using NTP. Just plain timer >> queries on a single system. >> >> My clock source is tsc which is the same for Xenomai I suppose. >> >> I wonder how a Xenomai task, even if it occupies 50% or even 90% of a 4 >> milliseconds time slice can interfere with the tsc. The tsc is not >> incremented via an interrupt, is it? But I do not know much about the >> inner workings of these functions. > > The problem is not the clocksource, the problem is the timer interrupt. > The kernel expects 1 timer tick every millisecond.
Not on archs that are CONFIG_NO_HZ capable. > When you run a > real-time task during 2 milliseconds and prevent the kernel from > receiving the timer interrupts, you certainly disrupt its timekeeping. > If you want to do this, switch the Linux kernel frequency (CONFIG_HZ) to > 100. Time keeping can perfectly bridge a lot of missing ticks as far as the underlying clocksource allows. And that's quite a bit with the x86 TSC. I wonder if the TSC is sufficiently stable here. Forgot to disable CONFIG_CPU_FREQ? How does your .config look like? Jan
signature.asc
Description: OpenPGP digital signature
_______________________________________________ Xenomai-help mailing list [email protected] https://mail.gna.org/listinfo/xenomai-help
