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Date: Fri, 12 Dec 2003 03:05:49 +1100 (EST)
From: Bruce Evans <bde@zeta.org.au>
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To: Andy Farkas <andyf@speednet.com.au>
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cc: Jeff Roberson <jroberson@chesapeake.net>
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Subject: Re: ULE and current.
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On Fri, 12 Dec 2003, Andy Farkas wrote:

> Bruce Evans wrote:
> > [about systat and top]
> > Neither; they have different bugs :-).  top actually seems to be
> > bug-free here, except it intentionally displays percentages that add
> > up to a multiple of 100%.  This seems to be best.  You just have to
> > get used to the percentages in the CPU stat line being scaled and the
> > others not being scaled.
>
> So the almost-bug in top(1) is that some CPU percentages are scaled and
> some are not scaled?

Yes.  It's probably more of a documentation bug.

> ps. You mentioned "jitter". Thats why I 'sleep 120' in the above tests.
> It tends to take about that long for top(1) to settle down. Why is that
> so?

As all top watchers know, %WCPU and especially %CPU take a while to
ramp up with SCHED_4BSD.  That's just how the algorithm works.  I don't
really understand SCHED_ULE, but think it has more jitter in the
percentages because it fakes them based on what it is doing based on
much less history than SCHED_4BSD (so they are closer to the transient
%[W]CPU than the long-term averages).

Bruce