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SubjectRe: HRTimer causing rtctest to fail
On Wed, 28 Feb 2018, Felipe Balbi wrote:
> Thomas Gleixner <tglx@linutronix.de> writes:
> > All numbers in micro seconds! What happens if you load the system or
> > restrict C-States?
>
> added intel_idle.max_cstate=0 to cmdline. Still see some failures,
> albeit a lot more rare, for example, caught one on iteration 8 of
> 8192Hz:
>
> 8192Hz: 1 2 3 4 5 6 7
> PIE delta error: 0.000135 should be close to 0.000122
>
> That is, however, only 13 uS late. Is that within the limits of "we
> don't quite care"?

I think so. 13us (depending on the machine) can easily happen if multiple
interrupts/timers happen at the same time or if something keeps interrupts
disabled for a few microseconds which is certainly possible.

What kind of system is this?

> BTW, it took some effort to get that one failure. I'll leave rtctest
> running in a long loop and try to figure out approximately how frequently
> it fails, but it seems like it's within the realm of "don't care", would
> you agree?

Yes.

Thanks,

tglx

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