I'm using Ubuntu 15.10 on my HP ProBook 6470b laptop. When I lock it and walk away from my desk it often gets very hot, very quickly.

Here's a screenshot of Psensor graph which shows the problem, the temperature started to raise just after I locked the device.

Sensor graph

Answer: Yeah, it was compiz. No, I don't yet know how to fix it

I was trying to find the root cause of this, but I'm running out of the ideas. More details about my setup:

  • This is my work computer, it runs in Windows-based corporate environment.
  • The computer is usually docked into station, but the problem also appears when its undocked.
  • The computer starts to cool down when I unlock it, without any additional actions.
  • No external devices (except Logitech mouse) are connected.
  • I'm using Compiz with Unity, pretty much default setup (I enabled some compiz plugins though, I love them).

So far I tried:

None of that helped.

Next, I started a tiny command logging CPU usage every 3 seconds, to identify the processes responsible for the problem: while true; do date >> logfile.txt; ps -eo pcpu,pid,comm | sort -k 1 -r | head -10 >> logfile.txt; echo -e '\n-----------------------\n' >> logfile.txt; sleep 3; done

Do not use ps for this. Use top: top -b >> logfile.txt

When I came back to my desk and heard the laptop's fans running at full speed, I checked the logfile immiediately - it turned out, that... nothing actually eats the whole CPU. The most CPU-intensive application was indeed compiz, but it used 3.2% of the CPU at most. during the whole time, there was no indication of any process going mad. Here's a sample log frame:

 3.1  2732 compiz
 2.1  3510 chrome
 1.8  1141 Xorg
 1.4  3566 chrome
 1.4 24014 evolution
 0.9  3733 chrome
 0.9 21418 firefox
 0.8  3489 psensor
 0.4  4164 abiword
 0.3 20256 chrome

Do you have any idea what I could do next to fix the issue, or at least find the cause?

  • I am afraid I am not familiar enough with ps to understand what is going wrong but ps is clearly not capturing all the processes running, or whatever is going on stops whenever you run your script. PSensor can see the high CPU utilisation. If you can run this and get the output why dont you do the same with top? – Steve Roome May 29 '16 at 19:20
  • @SteveRoome head -10 limits the output to 10 lines and processes are sorted by CPU usage. Anyway, I can drop this out and check (well, maybe there's a thousand of 0,1% processes?) – user1234567 May 30 '16 at 6:20
  • 1
    I just cant see this as a likely scenario. It's not the display and sorting I can't understand. It's the section in the ps man page on the selection of processes to display. Default is processes owned by the current user and tied to the current display. – Steve Roome May 30 '16 at 8:13
  • Before you lock the screen, run System Monitor (command: gnome-system-monitor), keep it running, lock screen, wait, unlock and check the CPU History graph. – user423626 Jun 3 '16 at 12:58
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    Sounds like Compiz bug 1322751 to me. Add yourself to the "I have this bug" list. – Steve Roome Jul 9 '16 at 9:40

I noticed some heat issues with Ubuntu as well, that is to say I really noticed the heat after picking up a very hot idle laptop.

Ultimately for me the solution was as simple as a can of well applied air duster to make sure the cooling system could function more efficiently.


compiz is a windowing manager. This may be common knowledge. But some comments hint it is not. Some (many?) HP laptops are designed such that the CPU and Graphics Processor share the same heat management resources. If we assume the CPU is cool and the Graphics Processor is over loaded, this explains how Psensor can report hight temperatures and low CPU usage. And, assuming speed mitigation utilities only work on the CPU, this also explains why such utilities are ineffective in managing this over heating problem.

I have observed episodes where "top" ranks compiz at 120% CPU usage and Psensor reporting centigrade temperatures in the 80s.

Also of concern. HP has a history of badly managing Graphic Processor head mitigation.

This article contains many good ideas worth exploring. However, the best solution may be to consider a different graphics driver or a simpler desktop. Look for "D. Try a lighter desktop environment" in the above link / article.

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