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 Post subject: Munin CPU
PostPosted: Wed Jan 21, 2009 7:31 pm 
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Joined: Wed Jan 21, 2009 7:13 pm
Posts: 126
Location: Portugal
Hi,

New costumer here.
I'm using my linode for a month and yesterday after full testing it went live :)

I have a question about munin if you can answer.
I'm using ubuntu 8.10 32 bits and munin stats for CPU are wrong:

Image

Anyone knows why?

Thanks


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 Post subject: Re: Munin CPU
PostPosted: Wed Jan 21, 2009 8:27 pm 
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Posts: 594
nfn wrote:
Anyone knows why?


What does top or htop show?

James


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 Post subject:
PostPosted: Wed Jan 21, 2009 11:29 pm 
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AOL: derole
i can't see the image you posted (it's just not loading) but i think i know what you mean, i have a similar "problem".

munin shows the CPU on a scale from zero to 400% making it hard to see anything meaningful.

Problem is that the linode runs with 4 processors so my guess is that munin simply adds up all the individual percentages (htop shows 4 individual processor indicators as well).


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 Post subject:
PostPosted: Wed Jan 21, 2009 11:43 pm 
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I don't see anything wrong either....

Your munin graph is showing 5-10% CPU utilization for the day, which is normal for websites that don't get hit too hard.

In fact, you should be alarmed if you see anything visually meaningful on that graph, because in that case something is probably consuming more CPU than it should.


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 Post subject:
PostPosted: Thu Jan 22, 2009 6:18 am 
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Hi, I can't paste top at this time because I'm on my mobile, but I think the problem can be the scale.


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 Post subject:
PostPosted: Thu Jan 22, 2009 7:01 am 
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nfn wrote:
... I think the problem can be the scale.


No problem, then. The peak CPU scale is correctly shown as 400%, since your Linode has 4 CPUs, and CPU usage that occasionally reaches - but does not stay - as high as 400% is generally OK at Linode. My CPU usage can sustain 100% or 200% for several hours if someone is surface fitting a large data set, although that does not happen very often.

Image

James
http;//zunzun.com


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 Post subject:
PostPosted: Thu Jan 22, 2009 11:51 am 
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Joined: Wed Mar 26, 2008 12:42 am
Posts: 6
Website: http://www.lafferty.ca/
Location: Toronto, Canada
No, that graph isn't right, because Munin graphs idle time too. Here's one:

Image

(not a linode, I wanted something with visible CPU usage!). As you can see, it's an area graph that fills the whole are up to 100*cpus % with system time stacked above idle time stacked above user time.

The "NaN" in the "Idle" line on nfn's graph above is the problem, but from here it's a matter of looking at the munin-node "cpu" plugin to see why it's failing. Here's the output of one of mine:

Code:
# /usr/share/munin/plugins/cpu 
user.value 32245294
nice.value 1187
system.value 13282284
idle.value 2151614388
iowait.value 2934277
irq.value 1153
softirq.value 1728224


What do you get when you run that command manually?


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 Post subject:
PostPosted: Thu Jan 22, 2009 1:16 pm 
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Here is the result of my linode:

Code:
user.value 240019
nice.value 151044
system.value 85593
idle.value 188229895
iowait.value 156121
irq.value 0
softirq.value 1083


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 Post subject:
PostPosted: Thu Jan 22, 2009 2:10 pm 
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mendel wrote:
No, that graph isn't right, because Munin graphs idle time too.


I also see the idle time is not graphed properly by munin 1.2.6 (Ubuntu 8.10 default version) on a Linode with the most recent kernel version, see:

http://www.linode.com/forums/viewtopic. ... n&start=15

The most recent development version of munin apparently works properly.

James


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 Post subject:
PostPosted: Thu Jan 22, 2009 2:42 pm 
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Hi,

I'm using 2.6.28-linode15 kernel and munin 1.2.6.
Should I downgrade to a lower kernel version? wich one?


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 Post subject:
PostPosted: Thu Jan 22, 2009 7:28 pm 
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nfn wrote:
Should I downgrade to a lower kernel version?


The problem is in the Ubuntu default version of munin, and only affects the display of idle time - it's not colored most of the time. Everything else is just fine. No need to change kernel versions.

James


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 Post subject:
PostPosted: Thu Jan 22, 2009 7:43 pm 
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Hi James,

But how am I able to get this to work?

Thanks
Nuno


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 Post subject:
PostPosted: Thu Jan 22, 2009 10:02 pm 
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nfn wrote:
But how am I able to get this to work?


It works now - any part of the graph that is not colored is idle time.

James


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 Post subject:
PostPosted: Thu May 28, 2009 2:44 pm 
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Joined: Thu May 28, 2009 2:37 pm
Posts: 7
This is still broken, the rrd file is showing NaN values for idle. I'm wondering if this is a Xen related bug.


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 Post subject:
PostPosted: Thu May 28, 2009 3:04 pm 
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Posts: 103
AOL: derole
not sure what you're talking about.
my munin graphs show up just fine with currently about 390 for idle (4 processors)


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