Need help to diagnose slowdown problem

Samuel Gilbert samuel.gilbert at
Wed Dec 22 09:16:28 PST 2010

Hello everyone,

  Ever since I've started using KDE4 on 3 different systems, I'm having 
performance problems.  Here is what happens :

After working in a session for a while the Xorg process starts to take more 
and more CPU.  I will generally notice it when some actions such as scrolling 
in dolphin or typing in kmail are totally unresponsive.  The subjective effect 
is like running remote X applications through a slow 56.6Kbps modem 

I have found a 100% reproducible way to trigger the problem : All I have to do 
is to use digiKam's aspect crop tool on about 30 photographs.

When the problem occurs, the X server process will take around 10~15% CPU when 
there are absolutely no events going on.  Doing thing such as switching 
windows or scrolling in a existing window (Firefox, dolphin, ooffice, etc..) 
will cause the Xorg process to jump to 100% CPU usage.  Closing windows will 
help a little, but the only way to get Xorg to behave properly once again is 
to completely restart the session.

I have tried to disable composting both in KDE and directly in 
/etc/X11/Xorg.conf to no avail.  The problem occurs on 3 different systems 
that do not have the same versions of software components.  Here are the 
common factors :

Linux x86_64
Nvidia graphic cards (9400M, NVS 160M, 8300)
KDE >=4.4.2
Xorg >= 1.7.6

Two machines are laptops with Intel Core 2 CPUs and the other one is a desktop 
with an AMD CPU.  I also checked ~/.xsession-errors and /var/log/Xorg.0.log, 
but I didn't find anything that looked helpful to understand the issue I'm 

Any help and suggestions on how to diagnose what's going on will be greatly 

Cheers and happy holidays,

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