Re: CPU load

[malc]

On Mon, 12 Feb 2007, Pavel Machek wrote:

> Hi!
>
> > The kernel looks at what is using cpu _only_ during the
> > timer
> > interrupt. Which means if your HZ is 1000 it looks at
> > what is running
> > at precisely the moment those 1000 timer ticks occur. It
> > is
> > theoretically possible using this measurement system to
> > use >99% cpu
> > and record 0 usage if you time your cpu usage properly.
> > It gets even
> > more inaccurate at lower HZ values for the same reason.
>
> I have (had?) code that 'exploits' this. I believe I could eat 90% of cpu
> without being noticed.

Slightly changed version of hog(around 3 lines in total changed) does that
easily on 2.6.18.3 on PPC.

http://www.boblycat.org/~malc/apc/load-hog-ppc.png

--
vale
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