Re: [chrony-users] Timeout for initstepslew?

On Tue, Sep 24, 2019 at 12:10 PM Bill Unruh <unruh@xxxxxxxxxxxxxx> wrote:

Actually setting a high poll rate does not necessarily get you a better sync.
It determines the offset more "accurately" but determines the rate worse. Ie,
if clock A gets its time from clock B, then the rate of A will jump around
much more if the poll interval is shorter. Now you may not care about the
clock rate, in which case short poll intervals are better, but that would also
mean that time differences would be much more random. Also if you lose clock
B, then clock A will drift away from the "correct" time much more rapidly.

Also, if in the short term, clock B say heats up (due to some program running
on B) A will try to follow that change in timing on the short term.

Ie, you need to think carefully about what you want from your clocks, before
you simply say "shorter poll intervals are better".

You could also set up a polling of the computer running B and only start
chronyon A when B actually comes up.

What do you use for timing clock B? If B uses A as its source and A uses B,
you can get problems with runaway behaviour. B tells A to speed up. A then
tells B to speed up, and way they go.

William G. Unruh __| Canadian Institute for|____ Tel: +1(604)822-3273
Physics&Astronomy _|___ Advanced Research _|____ Fax: +1(604)822-5324
UBC, Vancouver,BC _|_ Program in Cosmology |____ unruh@xxxxxxxxxxxxxx
Canada V6T 1Z1 ____|____ and Gravity ______|_ www.theory.physics.ubc.ca/

On Tue, 24 Sep 2019, Zack Shivers wrote:

> Good to know these are equivalent!
>
> If I used this config, it will permanently set the poll rates for this
> server, correct? Since this is a local setup, I'm using a high poll
> rate (-3) to get a better sync. Setting the timeout as a function of
> the poll rate is not ideal.
>
>
>
> On Tue, Sep 24, 2019 at 12:55 AM Miroslav Lichvar <mlichvar@xxxxxxxxxx> wrote:
>>
>> On Mon, Sep 23, 2019 at 05:20:12PM -0700, Zack Shivers wrote:
>>> I ask about the timeout on initstepslew is that the problem would be
>>> solved if I could set a much longer timeout than 10 seconds. The
>>> makestep option could work instead, but I've seen issues using this as
>>> well that I will post about later.
>>
>> initstepslew is basically the same as a "server ... iburst" and
>> "makestep" together. iburst in initstepslew will send up to 6 requests
>> in 2 second interval, which is about 10 second total. If you need to
>> send more requests and keep the short interval, you could use the minpoll
>> and maxpoll options instead of iburst. For example:
>>
>> server host1 minpoll 1 maxpoll 1
>> makestep 0.1 3
>>
>> Please let us know what are the issues with this approach.
>>
>> --
>> Miroslav Lichvar
>>
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>
>
> --
>
> Zack Shivers
> Electrical / Embedded Systems Engineer
>
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