[users at i-scream] libstatgrab on AIX: data mismatch between saidar and topas

Jens Rehsack rehsack at gmail.com
Mon May 23 17:02:49 BST 2016


> Am 23.05.2016 um 17:02 schrieb Anderson Carlos Trindade <anderson.trindade at optimode.com.br>:
> Hello List,
> I’m trying to understanding some differences between data reported by AIX utility topas and saidar.
> On a given moment (almost in the same second), saidar report the following CPU usage:
> CPU Idle: 88,28%
> CPU system: 4,72%
> CPU User: 7,00%
> but topas report the following usage:
> %Idle 35,8%
> %Kern 3,5%
> %User: 60,5%
> %Wait 0,2%
> It seems that both utilities are using different sources of data, since the usage reported is very different.
> Please, could you help me to understand where these differences are coming from?

Well, I don't know where topas is fetching it's data from - and where your topas comes from (AIX Linux Tools? 3rd party repo?) ....

As you can see here https://github.com/i-scream/libstatgrab/blob/master/src/libstatgrab/cpu_stats.c#L162, libstatgrab is using perfstat - the IBM recommendation and the same source used by nmon.
See https://www.ibm.com/support/knowledgecenter/ssw_aix_53/com.ibm.aix.prftools/doc/prftools/prftools07.htm%23wq407 for more details about libperfstat.

The reason for enhancing libstatgrab by a former customer was the poor data quality of GNU tools on Unices (HP-UX, AIX, Solaris).
When I'm in doubt, I trust libstatgrab more than all GNU tools together >:-)

> my apologies in advance, because I'm very new on AIX world
> This is a LPAR with 4 CPU’s

Best regards
Jens Rehsack - rehsack at gmail.com

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