Monitor Linux system CPU usage

[bbrendon]

Does anyone have a good way to monitor over-all CPU usage on a linux host?

I have been using:

system.run[sar -P ALL 1 2 | grep 'Average.*all' | awk -F" " '{ print  100.0 - $ NF }']

The problem with the above, is that on some hosts I get "Not Supported" intermittently even though running it from the command line works fine 100% of the time. I'll re-enable it and it'll work again for a day, and then stop working.

[sterno]

You have problems because "sar -P ALL 1 2" takes 2 seconds to complete, which is too long for a userparameter.

I use a script that looks at the performance counters under /proc/stat, calculates a percentage based on deltas from its last run, and stores the new numbers for the next run. I'm not sure how useful a measure that really is, though. It's easy enough to say that user/nice/system and interrupt handling are all "activity", but iowait is a bit of a gray area - the system isn't really doing anything, but it's not really idle either.

[bbrendon]

I make a pretty drastic effort to not use extra scripts because it means I have to make sure those scripts are on all the servers and are updated, which would be almost impossible.

It would be really nice if this was built into the agent!

[mikecrowe]

You can also adjust the Timeout variable in the zabbix_agentd.conf. I set mine at 15s, because I'm doing a lot like this.

[mikecrowe]

... I use a script that looks at the performance counters under /proc/stat, calculates a percentage based on deltas from its last run, and stores the new numbers for the next run.

Could you share that please?

[sterno]

It's not perfect, but it seems to provide a reasonable estimate of the non-idle CPU time. Should be easy enough to customize, just check the kernel docs for the format of /proc/stat.

#! /bin/bash

umask 022
PATH=/usr/bin:/bin
LD_LIBRARY_PATH=
export PATH LD_LIBRARY_PATH

if [[ ! -r /proc/stat ]] ; then
        echo '-1'
        exit 1
fi

file="$1"
cpu="$2"

# No CPU - default to total
if [[ -z "${cpu}" ]] ; then
        cpu=' '
fi

# No filename - default to /var/run/zabbix/cpucounter
if [[ -z "${file}" ]] ; then
        file='/var/run/zabbix/cpucounter'
fi

typeset T=0 R=0
if [[ -f "${file}" ]] ; then
        . "${file}"
fi
rm -f "${file}"

exec awk "/^cpu${cpu}/ {
        run = \$2 + \$3 + \$4;
        tot = run + \$5;
        printf(\"T=%f ; R=%f\\n\", tot, run) >\"${file}\";
        tot -= ${T};
        if (tot > 0)
                run -= ${R};
        printf(\"%u\\n\", int(run / tot * 100));
}" </proc/stat