[Intel-gfx] [RFC] Glamor : a 2D rendering engine based on OpenGL for xserver

[zhigang gong]

Here are some preliminary performance data I got by using cairo performance
trace and x11perf on three different machines. We can see on SNB GT1 glamor
can get identical performance with UXA, and on Ironlake machine, glamor get
identical performance with SNA.

But on SNB GT2 machine, glamor's performance is much slower than UXA and
SNA. Need further effort to understand and further tune glamor on SNB platform.

             rgb10text(max/min)         aa10text(max/min)
firefox-planet(xcb) - cairo-trace
             (higher is better)              (higher is better)
(lower is better)

CPU      : i5-2500K @ 3.30GHz
GPU:  ( SNB GT2)

glamor       1.16M                        1.37M                10s
sna          2.19M/1.95M            2.88M/2.41M        4.2s
uxa             2.49M                       3.11M                5.1s
cairo-image       N/A                       N/A                  9.5s


CPU: i7-2600 @3.4GHz
GPU:  (SNB GT1)

glamor             1.21M               1.42M               10.1s
sna               2.12M/1.74M    2.58M/2.26M       10.3s
uxa                  1.2M                 1.39M                11.3s
cairo-image      N/A                    N/A                   7.5s


CPU: i5-480 @2.2GHz
GPU: (Ironlake)
glamor          772K                     913K                18.7s
sna               780K/1.02M        1.19M/1.34M      18.7s
uxa               693K                     935K                 32.9s
cairo-image      N/A                    N/A                   15.3s

On Wed, Aug 17, 2011 at 8:18 PM, zhigang gong <zhigang.gong at gmail.com> wrote:
> Hi folks,
>
> Glamor project was initiated by Eric at last year which is to implement a new
> rendering acceleration engine by using OpenGL to handle all the 2D operations.
> It is somehow very similar with UXA. The major difference is that we use texture
>  to hold pixmap if possible, and then use shaders to fill/composite
> those pixmaps,
> but UXA is calling libdrm to do buffer allocation and prepare/submit batch
> buffer to GPU to start the rendering.
>
> Now I'm working on this project, and add one ddx driver based on MESA/EGL
> for the Xorg server. We have two experimental xservers currently, one is Xorg
> with glamor ddx driver and the other is Xephyr. KRH suggested me to add GLES2
> support, now it's almost done. Glamor xserver could run with GLES2 with major
> color format support. Now it’s ready to move to wayland.
>
> After some performance tuning, we now can avoid most of the fallback path
> for common desktop applications. On some old platforms we can get identical
> or even better performance with UXA/SNA, for example on a i5-480M machine
> with GMA graphic chip. But on the latest SNB platform, there is still a big
> performance gap. On latest SNB machine,glamor can only get about 1/2 –
> 1/3 performance compare to UXA/SNA. The glyph rendering is the bottle-neck
> will further tune this part’s performance.
>
> I want to get some comments here from who may be interested in glamor
> before I move forward. From my point of view, if we can continue to improve
> glamor's performance, and to achieve identical or even better :) performance
> with uxa/sna then glamor could be a good candidate of new device’s ddx driver
> and can save many effort of writing new 2D drivers for each new hardware.
> Key point here is the performance. I discussed with Eric and we just saw one
> big limitation is the texture size limitation. Is there any other
> serious resctriction
> here?
>
> Here is a draft TODO list for glamor.  Ask for comments here too.
> Actually, Eric already told me some things I need to do.  adjust the
> priority according
> to his suggestion. Thanks Eric.
>
> 0. Ongoing effort:
>    Enable glx/dri2 support. Need to handle the communication between dri2
>    buffer and textures. One possible solution is to create a EGLImage from
>    the dri2 buffer object's handle. And then bind the image to a texture.
>
> 1. Testing
>    Verify with X test suite and rendercheck and make sure no regression.
>
> 2. Submit patchset to Xorg.
>     Not sure how to do this, who should I contact first? The patchset has three
>     parts logically, one is a glamor directory holds the hardware independent
>     rendering code. The second part is a patch to Xephyr which is to enable the
>     xephyr to use glamor. The third part is a simple ddx driver for xorg.
>
> 3. Further performance tuning.
>    Optimize glyphs rendering.
>         Current glyphs rendering code is based on a very old uxa
> implementation,
>         we should have some chance to optimize this part.
>    Large pixmap support.
>          Mesa only support rendering 4096x4096 texture and some OpenGL/ES2
>          even only support 2048x2048. This will enforce us fallback to use CPU
>          memory which is very slow.  I'm planning to use multiple texture to
>          represent one single large pixmap.
>     Fully optimize the gradient filling by using shader.
>     Support all compositing OPs.
>     Move 1bpp to texture (currently fallback to cpu memory).
>     Support all color format for GLES2.
>