Re: What to do about "WARNING: negative runtime; monotonic clock has gone backwards"

[Brad Spencer <brad%anduin.eldar.org@localhost>]

Taylor R Campbell <riastradh%NetBSD.org@localhost> writes:

>> Date: Thu, 20 Jul 2023 21:50:26 -0400
>> From: Brad Spencer <brad%samwise.nat.eldar.org@localhost>
>> 
>> With a DOMU kernel compiled with KDTRACE_HOOKS I get the following with
>> either of those dtrace probes on the DOMU:
>> 
>> dtrace -n 'sdt:xen:clock:, sdt:xen:hardclock:, sdt:xen:timecounter: { printf("%d %d %d %d %d %d %d", arg0, arg1, arg2, arg3, arg4, arg5, arg6, arg7) }'
>> dtrace: invalid probe specifier sdt:xen:clock:, sdt:xen:hardclock:, sdt:xen:timecounter: { printf("%d %d %d %d %d %d %d", arg0, arg1, arg2, arg3, arg4, arg5, arg6, arg7) }: "/usr/lib/dtrace/psinfo.d", line 46: syntax error near "u_int"
>
> Can you please file a PR about that, and pass `-x nolibs' to dtrace in
> the mean time?
>
> dtrace -x nolibs -n 'sdt:xen:clock:...'


Back to the original problem....

I got this on the console:

[ 159564.607341] WARNING: lwp 105 (system pgdaemon) flags 0x20020020: timecounter went backwards from (159565 + 0x60917da1f41f3971/2^64) sec to (159564 + 0x9b7aac0ce33a822d/2^64) sec in netbsd:mi_switch+0x112


I assume that this indicates some or other is going off the rails.


$ vmstat -e | grep -e tsc -e systime -e hardclock
vcpu0 missed hardclock                                16031340   92 intr
vcpu1 missed hardclock                                   53462    0 intr


The dtrace probes produced some amount of timecounter:backwards and tons
of hardclock:missed events.

The system is mostly idle right now with out the only thing going on
being a cvs update.  Some some amount of disk activity.



-- 
Brad Spencer - brad%anduin.eldar.org@localhost - KC8VKS - http://anduin.eldar.org