[svlug] CPU load and real world value

Michael Eager eager at eagercon.com
Sun Mar 20 12:05:12 PST 2016


On 03/18/2016 04:48 PM, Robert Freiberger wrote:
> Hello,
>
> I still consider myself pretty new to the world of UNIX/Linux, and find that when I investigate an
> issue with CPU load, it's very difficult to trace the issues. Unlike performance problems with
> network or NFS, where I can test latency with simple commands, load appears to be much harder to
> test in real time.

Are you familiar with "top" or the graphical variant "htop"?
Both will give a real-time display of current system load
and activity.  KDE and Gnome have graphical monitors for CPU
utilization and other activity, such as memory or network use.

Tecmint.com has an article about 20 different tools which can
be used to monitor Linux performance.

> Is there any recommendations how to really investigate this and how effective is CPU load to a
> systems health?

It's not clear what you are investigating.  Do you have a problem
or are you simply curious?

High or low CPU utilization is not a cause or solution to poor
performance.  If you are running at 80% CPU, that means that the
CPU is idle 20% of the time.  Any program which is ready to run
while the CPU is idle will be dispatched.  On most systems, reducing
CPU load to 60% will not make programs run faster, it will just increase
your idle time.  (This may not be true if you are running CPU-intensive
programs like transcoders or video editors.)

More interesting is load averages displayed by top/htop and
uptime.  This is the average number of runnable processes which
are waiting at any particular time.  High load averages result
in poor responsiveness.

-- 
Michael Eager	 eager at eagercon.com
1960 Park Blvd., Palo Alto, CA 94306  650-325-8077



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