Re: sudden appearance of timekeeping problems with netbsd-8 just after 8.1

[Greg Troxel <gdt%lexort.com@localhost>]

Greg Troxel <gdt%lexort.com@localhost> writes:

> I have a fairly normal amd64 computer that I've been using for several
> months without issues, tracking netbsd-8.  Until Sunday I was running
> 8.1_RC1 built on May 15.  I updated to 8.1_STABLE built from sources on
> June 3.
>
> Now, everything seems ok, except the system clock is losing massive
> amounts of time.  Over 31.25 minutes of real time, the system clock
> became behind 9 minutes.

I built daily kernels from source for May and most of June, and was
preparing to bisect, and then happened to reboot for some other reason.
This time, with the exact kernel that lost time, and without having
messed with the BIOS (but with the power having been off for a bit),
everything is fine with tsc.  relative  to the problem:

-timecounter: Timecounter "TSC" frequency 3920113160 Hz quality 3000
+timecounter: Timecounter "TSC" frequency 2800141480 Hz quality 3000

relative to the pre-8.1 kernel

-timecounter: Timecounter "ACPI-Safe" frequency 3579545 Hz quality 900
+timecounter: Timecounter "ACPI-Fast" frequency 3579545 Hz quality 1000

-timecounter: Timecounter "TSC" frequency 2800071320 Hz quality 3000
+timecounter: Timecounter "TSC" frequency 2800141480 Hz quality 3000

I still think something happened, as we have two reports but now I'm
thinking that the issue is sporadic miscalibration.  I will try to read
the ACPI-Fast code.

Thanks to everyone who sent hints.