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kern/56322: Excessive clock drift

>Number:         56322
>Category:       kern
>Synopsis:       Excessive clock drift
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Jul 22 00:15:00 +0000 2021
>Originator:     David A. Holland
>Release:        NetBSD 9.99.85 (20210623)
System: NetBSD valkyrie 9.99.85 NetBSD 9.99.85 (VALKYRIE) #7: Wed Jun 23 18:32:25 EDT 2021  dholland@valkyrie:/usr/src/sys/arch/amd64/compile/VALKYRIE amd64
Architecture: x86_64
Machine: amd64

Four days ago (and a couple hours) I noticed the clock was badly
behind, and synced it with ntpdate.

It is now on the order of 1:30 (that's one and a half minutes) behind,
by comparison to another machine that runs ntpd. This machine does
not, for no particular reason.

This is a regression - prior to updating to 9.99.85 the clock lagged
but nowhere near so much.

This is the relevant material I see in dmesg, which isn't much use.

[     1.000000] timecounter: Timecounters tick every 10.000 msec
[     1.000000] timecounter: Timecounter "i8254" frequency 1193182 Hz quality 100
[     1.000003] timecounter: Timecounter "clockinterrupt" frequency 100 Hz quality 0
[     1.051023] timecounter: Timecounter "TSC" frequency 3517182870 Hz quality 3000

Before this update I used to get messages of the form
   autoconfiguration error: ERROR: 2607 cycle TSC drift observed

These have gone away, but I suspect the underlying problem is that the
TSC is bad and this is no longer being detected.

Machine is a 6-way AMD Family 15h.

I don't want to be fixing the time regularly because I'm sure it will
regularly remind me of PR 56097. I could turn on ntpd, but that's at
best a bandaid, and with this much drift it might just lose sync



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