Re: Incorrect CPU process accounting using CONFIG_HZ=100

[Al Boldi <a1426z@gawab.com>]

Pavel Machek wrote:
> On Thu 2006-06-22 20:36:39, Al Boldi wrote:
> > Jan Engelhardt wrote:
> > > >Setting CONFIG_HZ=100 results in incorrect CPU process accounting.
> > > >
> > > >This can be seen running top d.1, that shows top, itself, consuming
> > > > 0ms CPUtime.
> > > >
> > > >Will this bug have consequences for sched.c?
> > >
> > > Works for me, somewhat.
> > > TIME+ says 0:00.02 after 70 secs. (Ergo: top is not expensive on this
> > > CPU.)
> >
> > That's what I thought for a long time.  But at closer inspection, top
> > d.1 slows down other apps by about the same amount of time at 1000Hz and
> > 100Hz, only at 1000Hz it is accounted for whereas at 100Hz it is not.
>
> It is not a bug... it is design decision. If you eat "too little" cpu
> time, you'll be accouted 0 msec. That's what happens at 100Hz...

Bummer!

Meanwhile, can't "too little" cpu time be made relative to CONFIG_HZ?

Thanks!

--
Al


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