xf86-video-ati has flawed drawing straight lines operation
Submitted by Zbigniew
Assigned to xf86-video-ati maintainers
I tried even newest 7.5.0 driver (with glamor module) - but it seems the problem still's here. At first I blamed Tk for the problem - but it turned out (after final comparison with NVidia), that the driver is flawed.
It seems, that (while using your radeon driver) Tk's canvas has about 5x more work with drawing "line" type objects than with drawing the same object (say: pentagram) as filled "polygon". The same can be noticed, when polygon is drawn with "-outline" option. It's easy to reproduce: just compare CPU load during execution of "Polyhedra" demo (from http://wiki.tcl.tk/14283 ), when drawing filled and wireframe corpses. Yes, I can see that wireframes are created there as polygons filled with black - but even when replacing relevant part of the code to create them as "line" objects - the huge difference in CPU load still remains (which can be seen especially on weaker machine, not strong modern multicore).
I don't use xorg.conf presently, just 2 lines in $HOME/.xinitrc
xrandr --output DVI-0 --mode 1280x800 --panning 1680x1050
(apart of a few keyboard-related ones)
When I ran the script on NVidia machine (with NVidia's proprietary drivers), the CPU load difference between the two "display modes" ("shaded" and "wireframe") was marginal, as expected.