Re: PSA: Clock drift and pkgin

How well can we trust your emulator to be fielding the correct number of 
interrupts? Because that is a non-trivial thing to handle in emulators.

40s in 1 hour is a horrible drift, and for a system not doing anything 
that seems extreme. I don't have the feeling that a real system have 
that much drift, which makes me wonder about the emulator...

   Johnny

On 2023-12-14 05:19, Mouse wrote:
> Okay, data point.
> 
> I brought up my KA630 emulator, running my 1.4T derivative.
> Single-user.
> 
> I then ntpdate-synced to my house chime (which is stratum 2 at the
> moment), slept for one hour, and re-ntpdated.  There was drift, and it
> was in the missed-interrupt direction.  There was nothing at all
> running to compete with anything.
> 
> # ps ax
>    PID TT  STAT      TIME COMMAND
>      0 ??  DLs    0:00.01 (swapper)
>      1 ??  Is     0:00.17 init -s
>      2 ??  DL     0:00.02 (pagedaemon)
>      3 ??  DL     0:00.28 (reaper)
>      4 ??  DL     0:00.20 (ioflush)
>      5 g0  Ss     0:03.46 -sh
>     25 g0  R+     0:02.40 ps -ax
> # ntpdate 10.0.1.1; sleep 3600; ntpdate 10.0.1.1
> 13 Dec 20:23:18 ntpdate[22]: signal_no_reset: signal 14 had flags 2
> 13 Dec 20:23:20 ntpdate[22]: step time server 10.0.1.1 offset 1.151316 sec
> 13 Dec 21:23:35 ntpdate[24]: signal_no_reset: signal 14 had flags 2
> 13 Dec 21:24:15 ntpdate[24]: step time server 10.0.1.1 offset 40.470697 sec
> #
> 
> It does take human-perceptible time to run something like ntpdate or
> ps (note that the delay between the second timestamp and the third is
> more than one hour).  But 40 seconds?  That's more than I can ascribe
> to command start delay, especially since I did another ntpdate while
> composing this mail and
> 
> # ntpdate 10.0.1.1
> 13 Dec 23:01:14 ntpdate[26]: signal_no_reset: signal 14 had flags 2
> 13 Dec 23:02:11 ntpdate[26]: step time server 10.0.1.1 offset 57.165556 sec
> #
> 
> both the amount of drift and the time it had to drift over were larger.
> That's 40.47 seconds in 1:00:15, 57.17 seconds in 1:36:59; solving
> 
> 40.47 = 3615 a + b
> 57.17 = 5819 a + b
> 
> gives me a=.007577132486... and b=13.0786660617....
> 
> I find it interesting that b is so large.  Perhaps I should take more
> measurements.  But I'm more interested in eliminating the drift than in
> figuring out its details.
> 
> I'll have to investigate more.
> 
> In my Copious Spare Time, of course. :-/
> 
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-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: [email protected]             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol