George Georgalis wrote:
> On Thu, Jan 11, 2007 at 06:46:30PM -0600, Jeremy C. Reed wrote:
> 
>>>I'm using a /bin/sh function to generate a the cpu utilization 
>>>
>>>util () { # CPU Utilization
>>> idle=$(echo "2 k $(top -b -d2 | grep '^CPU states' | awk '{print $11}' | sed 's/%//') 1 + p" | dc)
>>> echo "2 k 1 $idle / p"  | dc ;}
>>>
>>>That returns the inverse of the cpu idle % found in top.  I add
>>>1 to the value before I invert it to prevent divide by zero, so
>>>output is pretty much between 0 and 1.
>>>
>>>Running two top reports seems a pretty inefficient way to get the
>>>value.  I think I can tune top a bit, but is there a more direct
>>>way to get the measurement?
>>
>>Maybe "sysctl kern.cp_time" ?
> 
> hey that looks pretty good, but I cannot find any doc on it
> sysctl(8) mentions it; but no detail in (3) 
> 
> my best guess to the numbers is the number of 0.01 seconds elapsed
> per cpu, so idle athlon below increments idle time silghtly over
> 100 per second, while the idle 8 core opteron increments at a
> little more than 800 per second.
> 
> does that sound right?

Yes, but slightly wrong. Your one-cpu system will increment the counter 
according to the hz field in kern.clockrate. For your machine, that 
would be 100. The "slightly over" you are observing is because your 
sleep, followed by a command will not take exactly one second, but 
slightly more.
And your 8 cpu system also have a hz of 100, but since you have eight 
cpus, you'll have to multiply by that, which gives 100.

So the rate per second is (no_cpu * hz)
And to figure out the amount spent in different modes, just take the 
delta from the last sample of the specific, divided with the total delta 
of all the fields.

	Johnny