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Re: kern/56322: Excessive clock drift

Can you post

sysctl kern.timecounter

I assume the with the

ERROR: 2607 cycle TSC drift observed

TSC was not picked as timecounter on your system.

Can you try

sysctl -w kern.timecounter.hardware=i8254

and see whether that improves the situation.

I agree that ntpd is unlikely to curb that large drift.

ntpd will on correct a drift up to 43 seconds per day (500ppm).


On 07/22/21 02:15, wrote:
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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