Comment 6 for bug 562293

The issue is more general for me. After a while, and a few open windows (four virtual desktops), graphics performance turns sluggish with KMS. It doesn't just affect Firefox, but also other apps like Evince (looking through a PDF document becomes painful), Gnome-terminal and movie playback (Xv needs composite redirection disabled to avoid dropping frames in fullscreen). The slowness is much more prominent with larger/maximized/ fullscreen windows, rather than for smaller ones. I don't think I'm affected by a GEM memory leakage, as it looks like GEM objects are in fact cleaned up when closing X apps (allocation decreases).

My PCIE ATI X1400 graphics card has 128MB VRAM, system has 3GB. Right now, things are slow as molasses, and current GEM status is:
1699 objects
150470656 object bytes
0 pinned
0 pin bytes
0 gtt bytes
0 gtt total

I seem to be getting some messages about hpet timer in kernel log, together with sluggish graphics, but I don't know if it's related:
[...]
[19313.601918] CE: hpet increasing min_delta_ns to 113904 nsec
[19362.762508] CE: hpet increasing min_delta_ns to 170856 nsec
[20965.902711] CE: hpet increasing min_delta_ns to 256284 nsec

Running Compiz, Ubuntu 10.04 installed from RC, fully up to date as of now. I haven't tried living on the xorg edge, yet, but have tried a radeon driver git snapshot. It didn't really do anything for the performance problems I'm seeing with Lucid and radeon-KMS.