Comment 15 for bug 562802

Since this problem affects me, too, I did some test. Maybe the results can help to track down the problem.

I am running Ubuntu Lucid Lynx (32 Bit) on an AMD 64x2 4800 CPU with an NVidia 8800 GTS GPU on a 1920x1080 display. I am currently using the 195.xxx drivers from the repos but I also tested with vesa, nouveau and even the new nvidia-256.xxx -- only to realize that the selected driver doesn't seem to have an effect on this specific bug.

The problem is that Firefox makes Xorg use 100% CPU when initially displaying or when scrolling certain pages. On some pages this leads to heavy delays and scrolling turns out to be very jumpy. The effect is most noticable when grabbing the vertical scrollbar and quickly dragging it up and down.

It's not clear what exactly triggers the problem. There are long pages that scroll smoothly and short pages that stutter (even this one). But I found one page that reliably stutters on my configuration so I used that one for my following tests:

http://blog.thesilentnumber.me/2010/04/ubuntu-1004-post-install-guide-what-to.html

Before Lucid, I was using Interpid which came with Firefox 3.0.x (IIRC) where I didn't have the problem. So I downloaded Firefox 3.0.19 from mozilla.org and gave it a try on Lucid. When fully loaded, the above page "flies" with Firefox 3.0.19. Though it's quite long and contains many images, scrolling is fast and smooth.

Next, I tried with Firefox 3.5.19. Here the problem began: Scrolling stutters on the above page and makes Xorg take 100% CPU.

For fun, I also tried the current snapshot of Firefox 3.7 aka Minefield and amazingly: The problem has gone again! Minefield does not fly as fast as 3.0.19 but it did not stutter as 3.5.19 and 3.6.3 did.

BTW: I had no console outputs while running my tests.