[Bug 173541] High (0.60+, 1.00) idle load averages

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=173541

--- Comment #50 from Mark Millard <marklmi26-fbsd@yahoo.com> ---
(In reply to Alexander Motin from comment #46)

Quoting your #9 :

. . . if system is idle, its CPU may wakeup as low as two times per second.

But, the load average code is based on fixed 5 second sampling and
then a small variability is tolerated/introduced to avoid matching
a (nearly) fixed frequency activity accidentally matching. The
"fixed" turns into a fixed number of adjustments, such as 12, 60,
or 180.

Having anything like 30sec between steppings of the load average
adjustment, spreads the 12 steps case (60 sec @5 sec each intended)
out to something like 360 sec total for the 12 steps. (Also has
implications for widely variable time interval sizes.)

If that is really the case, not much else can matter as long as
the 5 sec interval is not well approximated and calling the
average a "1 minute" average can be highly misleading.
Descriptions that would be accurate are "12 step load figure",
"60 step load figure", and "180 step load figure". No fixed
conversion to time intervals available --and not really
arithmetic means.

Sound right?

Note:
For what I use the "load averages" for, the "N step load figure"
interpretation works fine without knowing specific times.
Inaccuracies in small figures (relative to the hardware
thread count involved) make no noticeable difference. Nor do
small percentage errors in the larger figures: Rule of thumb
material for making some judgments that are not highly sensitive
to the details.

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