Re: [chrony-dev] PPSAPI: kernel consumer

[Alexander Gordeev <lasaine@xxxxxxxxxxxxx>]

В Mon, 8 Feb 2010 13:45:11 -0800 (PST)
Bill Unruh <unruh@xxxxxxxxxxxxxx> пишет:

> On Tue, 9 Feb 2010, Alexander Gordeev wrote:
> 
> > ÿÿ Mon, 8 Feb 2010 09:16:48 -0800 (PST)
> > Bill Unruh <unruh@xxxxxxxxxxxxxx> ÿÿÿÿÿÿÿÿÿÿ:
> >
> > very simple and thus predictable. We need code to be predictable
> > because we run a hard real-time environment for distributed
> > simulation. chrony is surely more complex. Also my code outperforms
> > chronyd in
> 
> Then run your code. Adding your code to chrony will make chrony even
> more complex.

I still don't get the philosophy/complexity problems. BTW I don't have
any code to add to chrony.

I hope other chrony developers will still consider adding kernel
consumer support a valuable feature or maybe just add it to allow the
user to choose the possibilities.

> > convergence speed at least. But please do not think that I want to
> > lower value of chrony.
> 
> Lower the poll interval. It looks to me like your code is
> effectively using a poll level  of 1 ( ie testing every second)
> instead of the usual refclock poll level of 4. Just run chrony with a
> lower poll interval and see how it responds.
> 
> Doing this you decrease the response time, but also increase the
> random error ( a shorter effective interval over which chrony can
> average the rate to knock down the rate error-- you will effectively
> double the rate error.) It is a tradeoff. Now, chrony usually does
> not have a chance to hold 64 prior measurements because temp changes
> cause the rate to change deterministically before 64 intervals have
> been collected. Running at a shorter poll interval may make chrony
> more responsive and not decrease the accuracy. Try it.

I'll try it, thanks.

-- 
  Alexander

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