Re: [chrony-dev] PPSAPI: kernel consumer

[Alexander Gordeev <lasaine@xxxxxxxxxxxxx>]

В Thu, 18 Feb 2010 15:20:08 +0100
Miroslav Lichvar <mlichvar@xxxxxxxxxx> пишет:

> With the latest changes chrony using poll 2 is now able to correct a
> 0.5 second offset and get a 1us sync in less than 30 seconds.
> 
> This requires a good kernel though. Tickless kernels before 2.6.33
> accumulate tick/frequency adjustments only in half-second intervals
> which results in slewing errors up to 40 ms. There is also a strange
> bug causing frequency instability after changing tick value which
> persist for hours after the tick was changed. With 2.6.33-rc8 these
> problems seem to be resolved.

Cool! So chrony is "the other user" of adjtimex here:
http://git.kernel.org/?p=linux/kernel/git/x86/linux-2.6-tip.git;a=commitdiff;h=a092ff0f90cae22b2ac8028ecd2c6f6c1a9e4601

However this seems to be not very good for my kernel consumer that this
commit got merged into mainline. :(
I had issues with it in tickless mode. Without it the consumer is able
to achieve 1us sync in ~10 seconds. But with it something very bad
happened. I didn't know that it will reach mainline so soon so I just
reverted it. Now I have to deal with the issues.

Thanks for the info!

-- 
  Alexander

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