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When I'm in the room and leave my laptop sitting for a period of time, the screen goes black (powersave mode) and then almost immediately I hear the fan go into overdrive and the laptop and air blowing out the vent gets hot.

I was concerned what was causing this. If I move my mouse, the screen returns (lock screen) and the behavior continues. I type my password in and unlock and return to my desktop, and almost immediately things return to normal.

I was frustrated at not being able to diagnose what might be causing it (relatively new Ubuntu user) so I left sudo top running so I could see immediately the values upon unlocking the system.

While compiz is usually under 4% CPU usage while I'm logged in and using the system, when returning from idle I found that it is around 100%!

How on earth could it be using vastly more resources when I'm not using the system than when I am using it?!

I found this related question...
Compiz consuming lot of cpu when display is off in 12.04

I also found what appears to be this specific bug registered on LP...
https://bugs.launchpad.net/ubuntu/+source/compiz/+bug/1322751

This one seems almost related (the fixes didn't work however)
https://bugs.launchpad.net/ubuntu/+source/compiz/+bug/969860

I've tried the linked fixes (aside from the cpulimit one, that seems like it will obviously affect the problem, but far from a "fix".)

I see that the devs closed the LP bug, I'm willing to debug/investigate if someone can point me in the right direction!

EDIT: Additional verification, WIN+L (locks screen), CTRL+ALT+F1, sudo top, and you can see it is only compiz at 100% (+/-4%)

Community
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t.j.
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1 Answers1

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I developed health-check to help identify the kinds of activity of rogue CPU eating processes such as this. This will at least give some idea of what is going on as the first triaging step.

Install:

sudo apt-get install health-check

Monitor compiz for 60 seconds:

sudo health-check -r -f -d 60 -p compiz

..and that way we get to see if it is polling on zero timeout waits.

If you want to read more about what health-check can diagnose before you commit to using it, please refer to the project page.

Colin Ian King
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