Horrible Xrender performance in Xorg 1.6.2

[Alex Deucher]

On Wed, Jul 1, 2009 at 2:11 PM, Michael<macallan at netbsd.org> wrote:
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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.
>

XAA offscreen pixmaps stopped working at some point and as such they
were disabled.  Not sure if that was pre or post 1.4.x however.  XAA
is getting pretty bit-rotten at this point I guess.  All recent accel
work as gone into EXA.

Alex

> have fun
> Michael
>
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