firefox slowness with xorg 6.9.0

[Tommi Sakari Uimonen]

Hi.

Executive summary:
firefox rendering slow with xorg 6.9.0, fast with 6.8.x.
Has anyone experienced this?

Details:

Firefox about:config page scrolls (with mouse wheel) very slowly and xorg 
takes 99% cpu. Also some pages with lots of text (eg. 
http://www.fyslab.hut.fi/db/pub/publications.php ) and when some 
other window is on top of firefox. Even just moving mouse between these 
two windows is extremely slow, it takes seconds before focus changes 
(focus follows mouse)

I'm using debian unstable (also tried kanotix), both have xorg 6.9.0 and 
kde 3.5. Video card is ATI 7500. Firefox is 1.5

For reference, I have also oldish gentoo install with xorg 6.8.x and it's 
fast. top shows that X takes only about 30% and firefox 50% cpu while 
scrolling about:config page with mouse wheel while some other window is on 
top of firefox. Gentoo has firefox 1.0.4 and kde 3.4

I'm just compiling firefox 1.5 to gentoo to bring the two systems 
configurations closer to each other. Hopefully I accomplish a situation 
where only xorg version differs, and then I really can blame xorg for the 
slowness. It could be GTK slowness, because konqueror works fast with the 
same setup (same website and another window on top of konqueror)

Both systems use the same xorg.conf file.

It could be some of the extensions that cause the slowness, but I need to 
do some research first.

I'm just curious if someone has experienced the same and can give some 
hints what to do to make firefox rendering fast again.


Tommi Uimonen