openGL in xfwm4
lunarc.lists at gmail.com
Thu Feb 28 17:18:40 CET 2008
On 27/02/2008, Brian J. Tarricone <bjt23 at cornell.edu> wrote:
> Has anyone actually done any reasonable benchmarking of opengl-based vs.
> xrender-based compositing/rendering, and run it on a variety of cards
> with different drivers? I hear a lot of people throwing around "opengl
> is faster than xrender," but I see no proof of this. I occasionally see
> some similar benchmarks on planet.freedesktop.org, but nothing
> comprehensive, and nothing that tests more than a particular (usually
> experimental) driver version on a particular card.
> Even if opengl is shown to be faster, is this because using the card's
> 3D engine is actually faster than the 2D engine, or is is it because the
> drivers don't accelerate 2D as well as they could? Let's fix things
> where they need to be fixed; randomly picking things to change because
> "omg lulz opengl for teh win!" is never the way to go.
One reason it feels faster in compiz is that it keeps all of the
window pixmaps in memory so that the program doesn't have to redraw
when it is exposed. This eliminates the fraction of a second when you
uncover a bit of window that garbage is displayed. I suspect this
doesn't even rely on OpenGL, it just takes gobs of memory.
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