RE: onstat & vmstat CPU measurements
If you are using Sun kit these number aren't accurate due to the kernel not
monitoring usage correctly. Also ps, mpstat and vmstat calculate CPU usage
differently
Paul Watson
-----Original Message-----
From: John Shepherd [mailto:johnshepherd@iname.com]
Sent: 08 March 1999 21:00
To: informix-list@iiug.org
Subject: onstat & vmstat CPU measurements
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Greetings,
I'm trying to calibrate CPU utilisation on our system using onstat, "ps
-el" (both updated before and after a test job) and vmstat (updated
every second).
onstat's view of CPU utilisation appears to be pretty much consistent
with that reported by "ps -el", but these are reporting higher values
than those reported by vmstat.
I have taken into account that we are executing on a 6-way box and that
the vmstat averages across all 6 engines.
Any clues ?
Regards,
j
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Paul.
Thanks for your note. After a bit more digging, I found that the rounding
errors - due to the way that vmstat presents its results as integers - were
responsible for the discrepancies.
CPU utilisation as reported in "iostat" is shown to one decimal place. Using
these values, I get a much better correlation between the measurements.
Regards,
John
"Watson, Paul" wrote:
> If you are using Sun kit these number aren't accurate due to the kernel not
> monitoring usage correctly. Also ps, mpstat and vmstat calculate CPU usage
> differently
>
> Paul Watson
>
> -----Original Message-----
> From: John Shepherd [mailto:johnshepherd@iname.com]
> Sent: 08 March 1999 21:00
> To: informix-list@iiug.org
> Subject: onstat & vmstat CPU measurements
>
> This is a multi-part message in MIME format.
> --------------E764093C8005A6497F585126
> Content-Type: text/plain; charset=us-ascii
> Content-Transfer-Encoding: 7bit
>
> Greetings,
> I'm trying to calibrate CPU utilisation on our system using onstat, "ps
> -el" (both updated before and after a test job) and vmstat (updated
> every second).
>
> onstat's view of CPU utilisation appears to be pretty much consistent
> with that reported by "ps -el", but these are reporting higher values
> than those reported by vmstat.
>
> I have taken into account that we are executing on a 6-way box and that
> the vmstat averages across all 6 engines.
>
> Any clues ?
>
> Regards,
> j
>
> --------------E764093C8005A6497F585126
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>
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