[SunHELP] actual, not average CPU load?

Valery Yankin sosiski at gmail.com
Tue Mar 7 07:29:39 CST 2006

Brigance, Leslie V, WCS wrote:
> U might get close to what you want by using just the sar cpu command at
> 5 sec intervals with a count of 20 or 30.
> CPU is the default.  Keep in mind that the 1st couple of lines are
> pretty much meaningless.
> By this I  mean just (on the command line as root, of course)
> #  sar 5 20
> Which will give you 20 reports at 5 second intervals. You get much more
> rapid rises and falls in CPU usage.
> If you decrease your interval much below 5, the sar command itself
> starts to really distort your data.
> LesB
Thank you for the hint. However, sar shows a lot of info, but I still 
cannot use it since I need a per-process CPU load statistics.

> -----Original Message-----
> From: sunhelp-bounces at sunhelp.org [mailto:sunhelp-bounces at sunhelp.org]
> On Behalf Of Valery Yankin
> Sent: Tuesday, March 07, 2006 1:22 AM
> To: The SunHELP List
> Subject: Re: [SunHELP] actual, not average CPU load?
>    James Fogg wrote:
> Speaking from my experience, you are asking for a miracle.
> There are good performance tools available, but anything
> which gave you the kind of accuracy and timing you are asking
> for would carry so much overhead that the tool itself would
> distort your information to the point of uselessness.
> Hopefully others have better options/opinions for you.
> I'd agree with this, and add the following -
> Average CPU is a fine measure unless you are working with a real-time
> system. Since Solaris/SPARC is stable up to 100% CPU load, if a
> momentary resource hog consumes the system it doesn't matter. The
> average system response time is going to be reflected by average CPU
> load. Human users aren't very sensitive to brief load spikes. If you
> *are* dealing with something that is very response-sensitive then Unix
> is probably not the OS you should be working with.
> Thanks, James. Your point is clear. I would like to explain why the need
> for such
> h precise measurements. My aim is to monitor a process that receives
> data every
>  15 minutes and processes it for some short time. I need then to draw a
> graph t
> hat would show how long the process is busy processing the data. On my
> present
> graphs based on the results from `ps` I have something that resembles a
> cardiog
> ram. So, people are asking me "Hey, why is that process so reluctant to
> free the
> e CPU after the processing is over? Because on the CPU load graph we see
> a peak
>  rise, then the line goes flat for some time (processing occurs) and
> then it sl
> owly goes down instead of dropping. Why?" So I guess I need to make it
> clear fo
> r the colleagues that this is the way `ps` measures the CPU load time.
> The problem is, I am using sort of a factory-tailored Solaris
> installation with
>  a fixed set of tools, and it is forbidden to install anything else. So,
> no pkg
> _add for me.
> Valery.
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