[ntp:questions] how to change the runtime priority - AND crazy psycho GPS
hart at ntp.org
Sun Feb 5 07:32:55 UTC 2012
On Sun, Feb 5, 2012 at 01:54, Ron Frazier (NTP)
<timekeepingntplist at c3energy.com> wrote:
> I thought there was a way to override the application's built in priority
> selection, other than using task manager.
You may be referring to a command-line option to raise the priority.
That option makes a difference for ntpd on most platforms, but on
Windows it always raises to realtime (or high if lacking privilege).
> I may have to try the method you
> mentioned if my testing indicates it's necessary. Here's why I think it may
> be a problem. Take a look at the following loopstats file:
> Note that is has a number of discrepancies and jaggedy areas and
> discontinuities along the time axis.. It also has a maximum excursion of
> around 30 ms offset.
> Now look at this file:
> This is representative of what I've been getting from my USB GlobalSat
> BU-353 when I have it set on Above Normal priority after switching it with
> the task manager away from real time priority. Note that the scales are
> different if you chart it. There are no significant discontinuities and
> maximum excursions are in the 15 ms range. For a USB only device with no
> PPS, I think this is a pretty good chart. It seems to me, this is
> performing better. I'll admit I have to do more testing to confirm any
Please post again when you feel you have enough data for a valid comparison.
> Actually, I've diverted my attention to troubleshooting a worse problem.
> Once I figure that out, I plan to get back to the priority issue. After
> about 3 days of rock solid operation similar to the above chart, my GPS
> suddenly goes phycho on me. Offsets go wild and get up into the 100 ms
> range. See the next file:
> As you can see, this continued for about 12 hours until I got tired of it.
> I stopped the ntpd service. Unplugged the GPS. Waited 30 seconds. Then
> plugged it in again and restarted the ntpd service. Now I'm back to a
> little over a full day of rock solid operation again. I'm waiting to see if
> it freaks out 2 days from now. If anyone can help me determine what's up
> with that, I'd be very grateful. I have verified that the TWO sets of
> firmware in the device (one for GlobalSat and one for the SIRF III chipset)
> are up to date as well as the USB - serial driver in my PC. I suspect a
> design flaw in the GPS firmware, perhaps a memory leak, or maybe a similar
> flaw in the Prolific USB - serial driver. However, I'm just speculating.
That's a bizarre loopstats alright. In two 8 second intervals you go
from < 5 msec offset to 80 msec and back to less than 5 msec,
suggesting a wayward system clock. I wish I had more feedback -- this
is unfamiliar territory for me, though A Carver's recent post
regarding ntpd on netbsd/sparc had similarly wild loopstats, I don't
really have any clue what might be causing either problem.
> Here's my ntp.conf file:
> By the way, can you do attachments on this NTP Questions list. I think I
> read somewhere that you cannot, which is why I'm using dropbox. However, I
> may have to delete these files after a while..
Attachments and HTML are stripped by the mailing list. If space
and/or clutter are a concern, you might consider using a pastebin
website. Those often permit indefinite-lifetime posts (good until the
site goes away or has trouble).
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