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Re: problem with cpu user on linux, 4.8.2
From: |
Martin Pala |
Subject: |
Re: problem with cpu user on linux, 4.8.2 |
Date: |
Fri, 1 Dec 2006 18:41:11 +0100 |
I believe that monit shows correct information ;) It works this way:
1.) each monit cycle reads the average cpu usage from the /proc/stat
(total average across all cores as stated by linux kernel in the
first line of the input)
2.) counts the deltas of the user, system, wait and total cpu usage
between the current and last cycle and the appropriates percentage
monit is sampling according to the monit cycle length ... the value
provides the 'immediate' average for the last cycle.
The difference between 'top' and 'monit' could be in the sampling
method. i don't know the exact method which is used in 'top', but
some tools, like for example solaris vmstat use the progressive
increase to keep the trend and flatten the spikes ... it is based on
exponential decay, so even though the load may be at 100%, the tool
won't show the real usage immediately.
I'm running monit 4.8.2 on several DL380 with two dual core xeons and
don't see any problems regarding the CPU usage statistics.
Martin
On Dec 1, 2006, at 12:59 PM, Aleksander wrote:
Replying to myself, sorry.
I thought about this a bit and maybe the problem is, that monit
checks for cpu user usage on ANY of the cores, not the average that
top shows by default. "1" shows each core and one of the cores
might have really been at 90+, but that's OK by me, when the other
3 cores were mostly idle. The box was not overloaded.
So how does it behave exactly, I didn't find this in the manual.
Thanks,
Alex
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