Re: PSA: Clock drift and pkgin

On 2023-12-17 20:58, Johnny Billquist wrote:
> On 2023-12-17 16:45, Paul Koning wrote:
>>
>>
>>> On Dec 16, 2023, at 9:16 PM, Johnny Billquist <[email protected]> wrote:
>>>
>>> For what it's worth, I think these lines also suggest something is 
>>> wrong with the clock (this run under simh, simulating a VAX8650):
>>>
>>> [  91.2854336] WARNING: lwp 854 (sh): negative runtime: (-1 + 
>>> 0xfee8c21d5277ae5a/2^64) sec
>>> [  91.2854336] WARNING: pid 854 (sh): negative runtime; monotonic 
>>> clock has gone backwards
>>
>> That would be a different issue, though.  If interrupts are lost or 
>> clock tick interrupt rates are not accurate, the system time will be 
>> wrong.  But that would not cause the "monotonic" clock to go 
>> backwards.  A supposed monotonic value going backwards is just a bug, 
>> no matter what the clock source is doing.
> 
> For sure. But at least in my mind, this is what seems to be a problem 
> more in general. The comments about the time moving all over the place, 
> ntp having issues syncinc, and eventually just loosing sync altogether. 
> That is more than lost interrupts. Time for processes reporting 106% is 
> not a lost interrupt thing either. Something is seriously broken with 
> time on VAX in general, I suspect. But as the above was observed running 
> under simh, at this time I should not exclude bugs in simh as well.

By the way - another comment/reflection on this. I don't really 
understand how a monotonic clock could ever go backwards. That in itself 
seems to be something that would be a real bug no matter anything else. 
Independent of wether I would run it on simh or a real machine. Such a 
clock should only ever be possibly moving forward. But I won't exclude 
that maybe some bug in simh could cause this effect. It certainly needs 
more looking into. But right now I'm busy trying to just do a build 
if/when that succeeds, I plan to start looking at this some more if 
noone beats me to it.

   Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
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