[Glamor] Trapezoid performance regression with the shader enabled.

[Michel Dänzer]

On Mon, 2012-08-06 at 14:10 +0800, He Junyan wrote: 
> 
> The trapezoid generating speed of the shader is relatively slow when the 
> trapezoid area is big. We need to fallback to pixman
> when the trapezoid's width and height is bigger than 300 pixels to avoid 
> the regression of the benchmark you referred.

How did you determine the threshold of 300 pixels? It'll probably vary
depending on the relative performance of the CPU and GPU, right?


> I think the shader’s advantage is that it can calculate multi-pixels 
> concurrently and avoid uploading.
> Pixman’s manner is based on scan line, the edge of the trapezoid need to 
> consider anti-alias and pixman’s rasterization need to do
> some jobs here, but inside the trapezoid, it use memset to assign value 
> very effectively.

Might it be possible to optimize the shader based rendering similarly
for pixels inside the trapezoid?


-- 
Earthling Michel Dänzer           |                   http://www.amd.com
Libre software enthusiast         |          Debian, X and DRI developer