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Date: Mon, 21 Nov 2011 09:30:03 +0100
From: Luigi Rizzo <rizzo@iet.unipi.it>
To: Eugene Grosbein <eugen@grosbein.pp.ru>
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Cc: hackers@freebsd.org
Subject: Re: dummynet(4) kernel process CPU usage monitoring
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On Mon, Nov 21, 2011 at 01:23:22PM +0700, Eugene Grosbein wrote:
> Hi!
> 
> I need to draw graph of dummynet's CPU usage.
> "procstat -t 0" shows me TID (thread id) of dummynet kernel thread.
> "ps -Hxo time,lwp" shows me total CPU time consumed by this thread.
> 
> Now I see this time has 9 seconds increase during 60 seconds of real time.
> This should be 9/60=15% CPU usage, but "top -SHP" shows me 0.00% meantime.

apart from the scaling on number of cores (e.g. if you have 8 cores
the 15% becomes a bare 2%) remember that percentages are computed
with some kind of filtering (EWMA ?) so if the load of dummynet threads
is bursty, the filter might eat most of it.

not completely sure this explains a steady 0.00%, if that's is
what you are seeing

cheers
luigi

> Where is my error?
> 
> Eugene Grosbein
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