composite performance

[thomas klein]

I'm running xorg 6.8.1-RC2
X Window System Version 6.8.1.99
Release Date: 2 October 2004 + cvs

I'm using composite extension with the last xcompmgr on kde.

I'm on a shuttle with a geforce4mx embeded gfx card, an athlon2200, 
kernel 2.6.10, nvidia driver 6629.

I got Option "RenderAccel" "true".

mode 1280x1024 24bpp.

When I use kwrite / kate / kdevelop in full screen mode, scrolling 
text lags a lot.

If I resize the window to less than 50% of the visible screen, text 
scrolling become usable.

One very weird stuff is : 

resize => text scrolling become usable
switch to a desktop with an open window then back => same scroll speed
switch to an empty desktop then back => scroll speed > 2x (very 
usable).

It's hard to explain but reproducable

Is this normal (due to the actual state of composite extension) or 
does I got some configuration issue ?

thanks in advance,

t.
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