Re: kern/56322: Excessive clock drift

[Frank Kardel <kardel%kardel.name@localhost>]

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).

Frank

On 07/22/21 02:15, dholland%NetBSD.org@localhost 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)
> > Organization:
> > Environment:
> 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
> > Description:
> 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
> anyway.
>
> > How-To-Repeat:
> > Fix: