Indeed, by following posted guide performance in KDE4 does improve. Try it.
Excellent performance with both GTK (redrawing windows is finally instantaneous) and Firefox 3 (no more slowdowns with images getting displayed or resized, digg.com bug gone, scrolling and animated scripts are smooth). That's with my 8600GT. Looks like they did their job well.
The only remaining issue I'm witnessing concerns urxvt with a background image. It still takes a couple seconds to appear or to be resized.
You might be interested in using real transparency in urxvt as well, which performs good here. An example configuration would be
urxvt --geometry 165x55 -ut -sr -ls +st -fg white -tint darkblue -sl 1000000 --scrollColor darkblue --troughColor darkblue --depth 32 -bg rgba:0000/0000/3900/cccc
which starts an urxvt with a blue tinted transparent background, so you get your desktop image as background.
The problem occurs with InitialPixmapPlacement=2 only indeed.
however, this requires, afair, a composited environment (as you get with xcompmgr or by using compiz.) Transset should not be needed.
Please look at
which clearly demonstrates it.
I did not use transset or any other tricks.
please make sure to inform nvidia about that by sending a nvidia-bug-report.log (created with nvidia-bug-report.sh) and a how to reproduce description to either the email@example.com address or post it on nvnews.net.The problem occurs with InitialPixmapPlacement=2 only indeed.
So nvidia engineers can try to fix it.
Update on my rxvt-unicode with fake transparency performance issue: I recompiled it with only the features I wanted, which does NOT include Xft/freetype. Now it's as fast with InitialPixmapPlacement=2 as with InitialPixmapPlacement=1. Not sure what caused the issue.