Re: [chrony-users] Fwd: Chrony malfunctioning at beaglebones

[Nuno Gonçalves <nunojpg@xxxxxxxxx>]

On Fri, Nov 20, 2015 at 6:54 AM, Miroslav Lichvar <mlichvar@xxxxxxxxxx> wrote:
> Does the recompiled kernel have the same CONFIG_HZ as the one you
> tried before?

Yes.

I'm still collecting data to be more sure. But it looks for now:

1 - nohz=off does not have any effect.

2 - With a kernel without Dynamic ticks enabled the latencies are
actually always greater, and they increase with system load! They
still decrease if I have a periodic thread waking very frequently.

That is: Threads waking regularly and for short intervals decrease
latency. Threads waking infrequently but doing a log of work increase
latency.

So with this my conclusions for now are:

1 - Linux command line option nohz is broken.

2 - There is something else on the beaglebone happening beside (1)
nohz, (2) cpuidle, (3) cpufreq, that is affected by a thread waking
very frequently.

I will share some annotated plots in a few days to make this very
clear. Anyway do you have any idea what can be happening here? Maybe
some cpuidle states are being entered despite being disabled?

Thanks,
Nuno

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