945GM(E) screen rotation and slow GL.

Rob Kramer robk at starhub.net.sg
Tue Jan 13 17:51:40 PST 2009


I have an embedded board with 945GM chipset (1.8GHz Celeron M) connected via
DVI to a 1920x1200 screen. I'm trying to benchmark GL performance a bit
with glxgears, which should be good enough to give a rough estimate of the
device's capabilities. (Is there a better generic GL benchmark tool?)

When testing screen rotation to portrait mode, the glxgears framerate drops
from 51 fps (not too great to start with) to 1 fps. 

I remember in the past there were always dire performance warnings regarding
XAA and rotation; impact of shadow FBs and all that. Is that still a valid
concern for a modern setup, i.e. is GL expected to be sluggish/unusable in
rotated mode? Should I not use the 'rotate' feature at all, but rotate GL
geometries/textures myself, in my application? (that would be painful, I

Using kernel Xorg, drm, mesa are from Fedora rawhide. The intel
driver is git HEAD. For the driver, it doesn't seem to make a difference
whether I specify UXA or not.



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