Hi, Thomas Gleixner writes: > On Wed, 28 Feb 2018, Felipe Balbi wrote: >> Thomas Gleixner 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? 4 core Kabylake. >> 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. cool, thanks -- balbi