I have an applet in my Gnome Panel which shows me the current load of my CPU. This is important on my laptop because it's a slightly older machine, and so knowing when I should let it finish one task before starting another stops me from getting frustrated with it.

However, sometimes when the CPU is maxing out at 100%, and stays there for a while, it can be an indication that something has gone wrong and maybe I should kill the process.

However, I've noticed over years of using Ubuntu that the System Monitor never really informs me what's going on.

Take for example, this screenshot (the interface is in Japanese, but that shouldn't change the problem):

CPU Load

Just above the System Monitor itself is my panel applet, where the box filled with green just to the right of the battery indicator is also indicating 100% CPU usage.

Now look at this image:

enter image description here

Nothing is using any more than 7% of the CPU.

This seems to be very frequently the case - I dare say almost always - that when the CPU is maxing out, I can never see what is actually using those CPU cycles.

I have tried using HTOP at the command line as well, but the results are the same.

Why does the System Monitor always show me 100% CPU use in general, but never more than a few % when I look at the total of specific processes?

What am I supposed to do when I want to figure out what is using so much CPU time, should I want to to kill runaway processes, or at the very least know what the process is?

  • 1
    did you activate the view of "all processes" in the menu ? – Cédric Julien Jan 3 '12 at 11:02
  • @CédricJulien: Wow! No... I hadn't enabled that option... because I never looked for it... because I always assumed that was the point of the System Monitor, so I never imagined it was an option I should look for. Huh. Well... let me give that a whirl for a while and see if it helps. If it turns out that's the issue, then you should put it as an answer. – Questioner Jan 3 '12 at 11:12
  • alternatively you can use the console command top – Michael K Jan 3 '12 at 11:48
  • @MichaelK: As I mentioned in the question, I tried HTOP, which is the same thing so far as I know, but it also doesn't show me all the processes. However, maybe that's because I'm not selecting all the right options there, either. – Questioner Jan 3 '12 at 12:52
  • Did activating "all processes" solve this question? – coversnail May 24 '12 at 7:30

As suggested by Cedric Julien in the comments,

To view all the processes that are using CPU, when using System Monitor, go to the View menu and select All Processes

enter image description here

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