Ubuntu – SAR statistics on CPU usage

cpu-usagesarUbuntu

i have Ubuntu server with 2 processors.
top command show that mysql eats up to 195%.
sar shows the following:

08:30:59 AM     CPU     %user     %nice   %system   %iowait    %steal     %idle
08:31:00 AM     all     75.12      0.00      0.00      0.00     22.89      1.99

I the following questions:

Could please someone explain what does %steal means?

I found the following description in manual, but can hardly understand what does it means:

%steal 
Percentage of time spent in involuntary wait by the virtual CPU or CPUs while the hypervisor was servicing another virtual processor.

CPU usage of process computed as "%user" + "%steal"?

I understand that the following questions are general and answers can depends on many factors but i need just some guidelines: what to do, what to find out and so on. Any docs, links are appreciated ( I didn't find anything very useful. Just general information)

Is "%steal" value is fine?
What is the edge value for CPU usage when I should worry about it?

ps. not Linux DBA just dev.

Thanks!

Best Answer

Answering one of your question - Could please someone explain what does %steal means?

steal time is a metric that only has meaning in a virtualized computing environment. It represents the amount of CPU that is taken away from a virtual machine to serve other purposes.

BTW, are you running your Ubuntu server in a cloud/VMWare environment?

You may also find this presentation from IBM helpful, which explains what steal time is and why it exists.

Related Solutions

Linux – top command indicates a different cpu usage than sar command

Neither -- they're just giving a different idea of CPU usage.

Top's idea of CPU is "per-core" -- that is, "this program is using 100% of one core". A multithreaded program can, therefore, be using, say, "400% CPU" -- which makes the eyes water a little sometimes.

On the other hand, sar sees it as as a percentage of total CPU -- so on a 4 core system, one fully utilised CPU core will show as "25% CPU", and the 400%-using program will show as 100%.

There's also the issue of instantaneous vs long-term averages, but I'm going to assume that you've accounted for that.

CentOS – High CPU Usage at a particular time in the night

This is when the cron.daily scripts run... By default, it runs daily just after 4:00am.

From /etc/crontabs

SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=root
HOME=/

# run-parts
01 * * * * root run-parts /etc/cron.hourly
02 4 * * * root run-parts /etc/cron.daily <-- THIS ONE!!
22 4 * * 0 root run-parts /etc/cron.weekly
42 4 1 * * root run-parts /etc/cron.monthly

And in /etc/cron.daily.

The culprit is probably your mlocate.cron, which runs updatedb and can be quite intensive on some systems:

#!/bin/sh
nodevs=$(< /proc/filesystems awk '$1 == "nodev" { print $2 }')
renice +19 -p $$ >/dev/null 2>&1
/usr/bin/updatedb -f "$nodevs"

Best Answer

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Linux – top command indicates a different cpu usage than sar command

CentOS – High CPU Usage at a particular time in the night

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