Utkarsh as preparing a fix and asked me about reproducing it.
But it seems usual use cases like this won't show the problem:

# Track
sudo /usr/lib/sysstat/sa1 -C checknotick 2 /tmp/samine
# print
sar -u ALL -P ALL -f /tmp/samine


It might be that this is due to Ubuntu not having a fully tickless kernel
=> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1587265

Even with modern "leave the cpu alone" things that issue isn't exposed.
Like:
  CONFIG_NO_HZ_IDLE=y (which we have)
  pluse:
  GRUB_CMDLINE_LINUX_DEFAULT="isolcpus=2"


@Thorsten - is there a reasonable way to trigger the issue, because if there 
isn't (e.g. only with self built kernel and further steps) I'm considering this 
to be great to be fixed in recent versions, but not easily  qualifying for the 
SRU [1] policy.
There is always a tradeoff between potential regressions (low in this case) and 
the gain. But there is also the tradeoff between forcing everyone to download a 
new sysstat and the gain - and if the gain in this case is a super rare edge 
case setup with custom kernels - then I'm leaning to say that in that case one 
can PPA build a sysstat as well (or as always upgrade).
Hence I'm interested in learning about the ways you used to trigger this as it 
might be way more common than I think atm - please let us know.

[1]: https://wiki.ubuntu.com/StableReleaseUpdates

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https://bugs.launchpad.net/bugs/1921747

Title:
  Backport missing %gnice CPU value for tickless CPU in sysstat.

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