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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