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

[Jens Rehsack]

Hi Anderson,

given the libstatgrab ist compiled on your own and is most recent version, I'd need to dig into it to see what's going on.
Does ./examples/cpu_usage proves saidar or sample code?

Maybe truss output of saidar helps out to see what's wrong ...

Cheers,
Jens

> Am 23.05.2016 um 18:54 schrieb Anderson Carlos Trindade <anderson.trindade at optimode.com.br>:
> 
> Hi Jens,
> 
> Thank you for reply!
> 
> As far as I know, topas seems to be an AIX utility (https://www.ibm.com/support/knowledgecenter/#!/ssw_aix_71/com.ibm.aix.cmds5/topas.htm), but I can’t tel you where the data displayed by topas is coming from.
> 
> But let’s forget topas for a moment.
> 
> I got a sample code from IBM site (https://www.ibm.com/support/knowledgecenter/#!/ssw_aix_53/com.ibm.aix.prftools/doc/prftools/prftools07.htm%23wq407), which uses perfstat to report cpu usage statistics.
> 
> Then, I compiled this sample code and run in parallel to saidar, each one in a separated SSH session. While saidar is reporting around 80% of Idle time and 10% of user time, the sample code above (based on perfstat) is reporting something around 35% of idle time and 60% of user mode usage. I recorded a screenshot and I can share with you If you prefer.
> 
> Considering that saidar and the sample code above are getting data from the same source, why are these statistics so different?
> 
> 
> 
> 
> 
> 
> 
>> Em 23 de mai de 2016, à(s) 13:02, Jens Rehsack <rehsack at gmail.com> escreveu:
>> 
>> Hi,
>> 
>>> 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
> 

--
Jens Rehsack - rehsack at gmail.com

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 842 bytes
Desc: Message signed with OpenPGP using GPGMail
URL: <http://lists.i-scream.org/pipermail/users/attachments/20160523/7e21b790/attachment.bin>