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I have both the system monitors of KDE and GNOME. When I compare the CPU usage of a CPU intensive program, that of KDE reports a 30% usage and 3GB of memory while that of GNOME reports 300% of CPU and same -3Gbs - of memory!

So, my questions:

  1. Why they reported different CPU usage for the same program while they reported the same memory usage?
  2. What is the meaning of 300% CPU usage that GNOME system monitor reports?!

System Info: Redhat 6.6 (Santiago) - Kernel: (Linux 2.6.32-504.30.3.el6.x86_64) - GNOME: 2.28.2 - KDE: 4.3.4

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  • When a process is using more than a core you can have value like that. (100%*3=300%). It's strange however even for different ways to report it. Did you check it with top? ps> Welcome (out) on SuperUser. Is the test made with the same program doing the same things and with the same nice? Moreover, are the monitors showing the same quantity?
    – Hastur
    Commented Jul 25, 2016 at 14:18
  • I guess you are right, maybe KDE shows CPU usage out of all available cores. top produces same result as GNOME monitor. yes I run the program and have both monitors running at the same time.
    – Mohamed Moanis
    Commented Jul 25, 2016 at 14:23
  • There are many different applets that will work as system monitors. If you refer to some of them, maybe you should add a link to their homepage. BTW check for what they are showing. (Maybe there is the possibility to select overall CPU usage or something else...). PS> with top you can press 1 and open the single core usage...
    – Hastur
    Commented Jul 25, 2016 at 14:28

1 Answer 1

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CPU usage: cumulative vs average value.

A modern CPU has multiple cores.
If you have a process that is using intensively 3 cores it can be reported to use "300% of CPU usage", its cumulative value, as well as that value divided by the number of cores.

Sometimes it is more useful the first, some other the second. Often it is possible to choose as option.

Under KDE, when you press Ctrl-Esc, it starts the System Activity [1]

that is akin to the Microsoft Windows' Task Manager, Apple's Mac OS X's Activity Monitor and Gnome's System Monitor.

Stopping the cursor over one of the CPU values shown, you will see a mask with some information more.

enter image description here

If you right click on the bar were is written USERNAME, CPU... over CPU it will be open a pull-down menu with the possibility to divide the CPU Value shown (cpu usage) for the number of CPUs (core), or to show the full value.

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  • and actually if you press right click over CPU tab, you can choose to show the average or the cumulative.
    – Mohamed Moanis
    Commented Jul 25, 2016 at 15:18
  • :-) Ok, it's better to specify. On memory it gives even more options. For each column there are (or not) specific options.
    – Hastur
    Commented Jul 25, 2016 at 15:22

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