Each poll of a host's overview graph held a worker for one second between
two CPU samples. The answer now carries its sample, signed with the time
and the compute; the next poll sends it back and the usage is taken since
then, so a point is the average since the previous one (normally 5 s, at
most 15 s). Without a sample, or with one that is altered, older or from
another host, or when the host restarted, it is measured over one second
as before.
A sample is one reading; the busy share was mixed from separate readings,
counted guest time twice (it is part of user) and added half a percent.
A host that cannot be read leaves a gap in both graphs instead of a zero
CPU point and a broken memory axis.
