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.
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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