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Bug 692518 - processes can use more than 100% CPU
processes can use more than 100% CPU
Product: system-monitor
Classification: Core
Component: process list
Other Linux
: Normal normal
: ---
Assigned To: System-monitor maintainers
System-monitor maintainers
Depends on:
Reported: 2013-01-25 11:08 UTC by Alexander van Loon
Modified: 2013-02-09 19:56 UTC
See Also:
GNOME target: ---
GNOME version: ---

screenshot showing gnome-shell using 154% CPU (227.59 KB, image/jpeg)
2013-01-25 11:08 UTC, Alexander van Loon

Description Alexander van Loon 2013-01-25 11:08:57 UTC
Created attachment 234380 [details]
screenshot showing gnome-shell using 154% CPU

I started a Fedora 18 Live USB on my system. Because use LLVMpipe was used, the CPU was stressed quite heavily. So it happened that the gnome-shell process used more than 100% CPU. I could probably reproduce this on my system if I would start Fedora 18 from the Live USB again. Screenshot is attached.
Comment 1 André Klapper 2013-01-25 22:36:49 UTC
If you have more than one processor I don't see a bug here. :)
Comment 2 Alexander van Loon 2013-01-26 09:09:37 UTC
Yes, I do have a dual core CPU. I didn't expect this to be intended behavior, I would assume that all CPU's or CPU cores – whether just one or eight or even more – in a system would count for no more than 100%. Eventually you would start seeing numbers like over 1500% if you have two CPU's with eight cores in your system; I don't think that is supposed to be so?
Comment 3 Robert Roth 2013-02-04 22:16:52 UTC
In Preferences, on the Processes tab you can check the Divide CPU usage by CPU count checkbox, that will change the behaviour you expect. Some people do find it useful (as do I), but that is why we have the preferences there. 
The question here is what would we like to use here as a default setting? Maybe some users would agree that CPU usage above 100% is strange, and people who think that CPU usage above 100% is OK if you have more than one core, would not have any trouble finding this setting.
What do you think?
Comment 4 Alexander van Loon 2013-02-05 08:47:06 UTC
I didn't know about the existence of that preference. If you ask me it should be enabled by default so CPU use can never exceed 100%, otherwise many people will probably be confused.

My reasoning is that 100% is full use and that it can't be exceeded when applied to a CPU. What I object to most is that the current default (the setting disabled) assumes that the user knows how many CPU's/CPU cores are present in the system. Advanced users will know, but the average user does not. Therefore average users will be unable to interpret the meaning of the CPU usage.

What adds to the confusion is that in the "Resources" tab of System Monitor, the graph for CPU usage doesn't (can't?) exceed 100%.
Comment 5 Robert Roth 2013-02-09 19:56:08 UTC
I have set the default value to show the CPU usage divided by core count, thus I am marking this as fixed.

This problem has been fixed in the development version. The fix will be available in the next major software release. Thank you for your bug report.