[Xymon] CPU USAGE DISPLAY (CPU Statistics)

[J.C. Cleaver]

On Tue, July 29, 2014 9:05 am, Schwab, Jos wrote:
> Mark,
>         Lastly, I also see in the man pages for TOP in the bugs section
> (again on CentOS) the TOP author speaks to this very topic. He
> calls the intervals samples.  Here is that except:
>
> 7. BUGS
>        Send bug reports to:
>           Albert D. Cahalan, <albert at users.sf.net>
>
>        The top command calculates Cpu(s) by looking at the change in CPU
> time values between  samples.  When
>        you  first  run it, it has no previous sample to compare to, so
> these initial values are the percent-
>        ages since boot. It means you need at least two loops or you have
> to ignore summary output  from  the
>        first loop.  This is problem for example for batch mode. There is a
> possible workaround if you define
>        the CPULOOP=1 environment variable. The top command will be run one
> extra hidden loop  for  CPU  data
>        before standard output.
>



> _____________________________________________
> From: Schwab, Jos
> Sent: Tuesday, July 29, 2014 10:56 AM
> To: 'Mark Felder'
> Cc: 'xymon at xymon.com'
> Subject: RE: [Xymon] CPU USAGE DISPLAY (CPU Statistics)
>
>
> Mark,
>         I failed to mention that in the man pages for TOP in CentOS 6.5,
> the -d command line option is called the interval which I had read
> somewhere is used to average statistics over. I hope that helps
> make it more clear and understandable.



Oof: https://bugzilla.redhat.com/show_bug.cgi?id=174619

Well, the system / idle / user etc percentages that end up getting graphed
in xymon are actually coming from the vmstat command, being run on
rotating 5 minute intervals, so the top output doesn't have an affect on
those graphs (or alerting, really). That being said, that's fairly
confusing, and it's a bit disappointing that procps doesn't call that out
a little bit better in its batch mode.

As a quick workaround, you can add CPULOOP=1 to the end of
/path/to/xymonclient.cfg and it should be in the environment for the $TOP
call in xymonclient-linux.sh. ($TOP gets a -x test against it, so the
command itself can't be modified to include env.)

That being said, this seems patch-worthy to at least give a more accurate
visual output. Wonder how non-Linux `top`'s deal with this...


HTH,
-jc