Re: HRTimer causing rtctest to fail

[Thomas Gleixner]

On Wed, 28 Feb 2018, Felipe Balbi wrote:
> Thomas Gleixner <tglx@xxxxxxxxxxxxx> 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