KWin (KDE4 from rawhide) using way too much CPU (nvidia driver problem)

Anne Wilson cannewilson at
Tue Jul 15 16:27:43 UTC 2008

On Tuesday 15 July 2008 16:11:55 Vini Engel wrote:
> > The proprietary nvidia driver is known to have absymal performance, and
> > we can't fix it because it's proprietary. Blame nVidia. There's nothing
> > we can do about it.
> Well, it may not be the best driver out there but before Fedora 9 it did
> work very well for me. The fact is that my problem is not really related
> to performance, the overall performance of my machine is pretty good.
> The problem is that xorg and kwin use too much CPU, it doesn't bother me
> much apart from using more battery. If it doesn't jump up to 80% my
> machine goes ok, I have disabled some of the desktop effects and it
> improved.
> I think we cannot blame nVidia for this because what is being used here
> is the CPU and not the GPU. Unless there is clear proof that their drive
> actually causes it to happen the problem to me will be related to the
> way KDE4 is handling OpenGL for its 'special' effects.

There has been a good deal of discussion of this on the kde-devel list.  The 
problems do affect only some cards, but excessive cpu usage is definitely a 
symptom.  The fact that kde and nvidia have discussed the problem and that 
nvidia acknowledge it does mean that nothing can be done until nvidia have 
sorted it at their end.

The problem apparently stems from some parts of the driver which have, in 
theory, supported certain requirements for some years, but because programs 
have not been written to use the facility there has been little opportunity 
to see what happens in real-life situations.  KDE's pushing of the boundaries 
with 4.x is opening that area up.  NVidia appear to be willing to work to 
sort this out, so we must wait for them.


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