Need help to diagnose slowdown problem

Clemens Eisserer linuxhippy at
Wed Dec 22 09:48:33 PST 2010

Hi Samuel,

Usually you won't find log entries about slowdown problems unless
something goes really terribly wrong.

Are you using the proprietary nvidia driver or nouveau?

If you are using the proprietary nvidia problem, could you switch to
nouveau to see if the problem persists?

To really get to the root of the problem, you will have to do some profiling:
- Install all debugging symbolds for the applications involved
(including libc, gcc, xorg, kde, ...)
- When your system runs slow, use a system-wide profiler like sysprof
to see where cpu cycles are spent.

Good luck, Clemens

2010/12/22 Samuel Gilbert <samuel.gilbert at>:
> 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
> connection.
> 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
> facing.
> Any help and suggestions on how to diagnose what's going on will be greatly
> appreciated!
> Cheers and happy holidays,
>  Samuel
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