Horrible Xrender performance in Xorg 1.6.2
Michael
macallan at netbsd.org
Wed Jul 1 11:11:25 PDT 2009
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Hello,
we ( that's NetBSD ) are in the process of updating our in-tree
Xserver from Xorg 1.4.2 to 1.6.* - I noticed some problems when
porting my driver for the SGI O2's rendering engine:
- - anti-aliased font rendering performance went down the drain. In
1.4.2 I got >160000 characters per second in x11perf -aa10text, now
it's down to a mere 8000, just about what I'd expect with pure
software rendering. It still goes through the hardware-accelerated
composite functions though. What changed here? Also, drawing non-anti-
aliased text is not affected, it's still going at about 400000/s.
- - horizontal and vertical lines all of sudden fall back to software
instead of using the hardware-accelerated functions. I have no idea
why, other lines and other rectangle fills work just as before.
The driver uses XAA and we don't have a linear framebuffer which is
why falling back to software rendering isn't only slow, it gives
completely wrong results. The driver uses its own Composite() handler
instead of XAA's in order to catch all whatever-to-vram composite
operations - CRIME can accelerate them all and fallback to software
has to be prevented. Going through the changes in XAA didn't yield
anything that looks related.
Any ideas? Somehow I don't think any of this has much to do with the
driver or the underlying hardware.
have fun
Michael
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