On Tue, 29 Dec 2015, Helge Deller wrote:
> No, the patch below doesn't help.
>
> I still see:
> [ 644.916000] timerfd_settime: interval (sec=0, nsec=100000000) it_value
> (sec=0, nsec=100000000)
> [ 645.024000] timerfd_gettime: interval (sec=0, nsec=100000000) it_value
> (sec=0, nsec=103029949)
>
Right. It can't help. Sorry for the distraction.
Looking deeper I found the issue. It's caused by CONFIG_TIME_LOW_RES. See the
comment in hrtimer_start_range_ns(). We round the expiry time to the next
jiffies period to avoid short timeouts. Assuming you are running with HZ=250
this is exactly 4ms. So that's where your extra time comes from.
Not sure what to do about that.
Thanks,
tglx
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