Clock fuzzing bugs

Achim Gratz Stromeko at nexgo.de
Sun Nov 24 16:07:14 UTC 2019


Eric S. Raymond via devel writes:
> If we don't see any evidence of beat-induced quantization, I'm willing
> to say we drop this code.

Please don't invent gobbledeegok terminology.  "Beat-induced
quantization" is completely devoid of meaning.  Again, what we're
talking about is dithering and it is used to mask the error spurs from
quantization.  The reason for needing it is that the resolution of our
measurement is in nanoseconds, while the actual granularity of the clock
is larger than that.

You will see it if you either use an original rasPi 1 (which only has
microsecond clock resolution) or switch back to one of the old clock
sources with coarse granularity on other architectures.

Again, the first question is what these messages really mean.  I don't
remember seeing them on the rasPi at all, but I don't restart the
daemons very often there.  On my Intel machines I only see them just
after having started the daemon and only one to three times.  Which
makes sense, since that's when the daemon needs to determine the clock
granularity.  It also converges to a system fuzz that conforms to my
expectations about the clock used.  So there's nothing wrong about that
in this case.


Regards,
Achim.
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