Bug#648222: Significant 2D performance regression with ColorTiling

[Michel Dänzer]

On Don, 2011-11-10 at 18:01 +0100, Michal Suchanek wrote: 
> On 10 November 2011 17:46, Alex Deucher <alexdeucher at gmail.com> wrote:
> > On Wed, Nov 9, 2011 at 12:36 PM, Iustin Pop <iustin at debian.org> wrote:
> >>
> >> The recent upgrade of xserver-xorg-video-radeon from 1:6.14.2-2 to
> >> 1:6.14.3-1 enabled ColorTiling for my card, which in turn caused a
> >> significant performance degradation in 2D (yes, I understand it should
> >> make 3D faster, but I didn't know it should slow down 2D applications).
> >>
> >> I'm using plain 2D environment (openbox, no compositing, anything) and
> >> plain xterm (bitmap fonts, no AA, etc.). The speed of display text has
> >> changed significantly enough that I can "see" my mutt refreshing the
> >> inbox and drawing the lines.
> >
> > Tiling will speed up all rendering (2D and 3D).  However, it sounds
> > like you are using an environment that is mostly software rendering.
> > As such in order for the CPU to access tiled buffers, the GPU has to
> > copy them to a linear buffer before CPU can access it properly.
> 
> FWIW I have color tiling enabled and have no speed issues in urxvt -
> TrueType fonts, AA enabled, etc.
> 
> Unlike xterm urxvt (rxvt-unicode) uses some special font-rendering
> libraries, however.
> 
> If I understand it correctly xterm would use the in-server bitmap font
> rendering which the X server can accelerate as much as it wants.

Core bitmap fonts are completely unaccelerated so far with EXA. xterm
can also use Xft for font rendering via the -fa option though, which is
well accelerated.


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