XOrg weirdness

Adam Jackson ajackson at redhat.com
Tue Feb 27 23:11:14 UTC 2007


On Tue, 2007-02-27 at 23:07 +0000, Richard Hughes wrote:
> On Tue, 2007-02-27 at 17:42 -0500, Adam Jackson wrote:
> > Would also like to know whether the same slowdown happens when using
> > Option "ShadowFB". 
> 
> Using this option returns the console output to blindingly fast.
> 
> Do you want me to file this in bugzilla, or continue to debug this with
> OProfile?

Still would like some oprofile with symbol names for the non-shadowfb
case (although I have a reasonable idea), but yes, bz would be
excellent.

Re reasonable idea: Software alpha-blending of text just sucks.  In
principle g-t is double-buffered, so the composition should be something
like CA blend to the backing pixmap followed by blit to the front
buffer, and therefore the backing pixmap could come out of card memory,
which would turn the blit into hostdata upload, which isn't _that_
painful.  You could even damage-track the blending if you wanted,
although that might not be a win.  Plus if you start evicting everything
you do text blends to, you might not have a lot left in card memory.

Tough to say.

Also it's not clear whether this is just latent sucking, or something
introduced between FC6 and now.  Swapping out the X server to test might
be an idea, it should be reasonably independent.

- ajax




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