Puzzling clock offset spikes

Gary E. Miller gem at rellim.com
Thu Jul 5 17:13:15 UTC 2018

Yo Paul!

On Thu, 5 Jul 2018 09:53:05 -0700
Paul Theodoropoulos <paul at anastrophe.com> wrote:

> On 7/5/18 09:42, Gary E. Miller wrote:
> > Yo Paul!
> >
> > On Wed, 4 Jul 2018 18:37:46 -0700
> > Paul Theodoropoulos <paul at anastrophe.com> wrote:
> >  
> >> What changed: I'd poked around with assorted parameters of the
> >> "dwc" module, which apparently drives the USB subsystem. It got to
> >> where I'd added all of these dwc module options to
> >> the /boot/cmdline.txt:  
> > You are runnning USB on a timekeeping RasPi?  I stopped doing that
> > when I noticed it wrecked havok with my measurements.  Unplug!  
> I attach a microSD card in a USB adapter in order to perform backups, 
> but I do only intermittently - every few days to a week or so. I
> could probably leave it attached to the ntpVIZ Raspi 1 and rsync over
> the LAN though; I should probably do that, then I can back up on a
> more formal schedule.

That's unrelated to your issue, the timescale is very different.

> > Of course the ethernet goes through USB on the RasPi, so minimize
> > ethernet usage too.
> >  
> Latency, jitter, etc, are terrible over wifi, and I have pretty good 
> wifi.

Yup.  I avoid the WiFi on RasPis if at all possible.

> When I monitor the netdata graphs in realtime over the WAN, 
> there's no visible change to the metrics, and that generates a lot of 
> https traffic, so I don't think that's it.

Is your WAN on WiFi or Ethernet?

> That said, latency and jitter were terrible when I first got my raspi
> 1 a couple of years ago; I've never tried it on the 3, so perhaps
> wifi on the raspi 3 might not suffer those issues; I will have to
> look into that. It'd be nice to be able to untether the little devil
> anyway, so I could easily relocate it elsewhere in the house where
> ambient temps might be smoother. I will check it out!

WiFi ethernet extenders are now cheap.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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