Re: oS11.3/KDE4: X slows down after a few hours
Some hints about this.
1. Try to "Enable Direct Rendering" in KWin. You can do that easily right-clicking on any window titlebar and selecting Window Behaviour Setup | Desktop Effects | Advanced. If you haven't checked "Direct Rendering", check it.
2. How is it doing with InitialPixmapPlacement? Try 0 or 4.
For me, this is a memory leak, and it behaves a lot better with Direct Rendering than with Indirect Rendering. KDE 4.5 RC3 here.