Composite really slow

[Alex Deucher]

On Tue, 16 Nov 2004 10:43:02 -0600, Evan K. Langlois
<evan at coolrunningconcepts.com> wrote:
> Hi Everyone,
> 
> It could be my imagination, but it seems that the Composite extension is
> much slower in Xorg than in the freedesktop.org/kdrive combination.
> Even with xcompmgr off, I have issues if Composite is in the config
> file.
> 
> I've tried lowering my screen resolution and reducing color depth, which
> helps minimally, and if lowered enough I can compare the freedesktop.org
> X server with Xorg, and while Xorg is more correct in its output, it
> should be MUCH faster than kdrive based servers.  Its not.  It performs
> as expected with Composite turned off, but the freedesktop.org X server
> is plenty fast with this feature, and xcompmgr can be run (normally off
> when I run Xorg) and even with shadows and fade effects its faster than
> Xorg without the features (and Composite turned on).
> 
> I'm using the Radeon driver that ships with Xorg (not the binary) with
> an ATI Radeon 9200SE with 128MB of RAM.  In my normal 1600x1200x24 bit
> its night and day.  I'm wondering if Xorg is using my slower desktop RAM
> (only 256MB and PC100 on a K6-2/550) for the off-screen bitmaps instead
> of the 128MB on the card.  With Composite enabled, X uses nearly all the
> CPU and apps suffer badly.  With it turned off, its quite snappy and
> very useable.
> 
> Ideas?  I can post my Xorg if someone wants it but until then, I won't
> waste the bandwidth as I have wacom drivers and all sorts of stuff in
> there, so its kinda long.
> 

Xorg is much slower than kdrive when it comes to composite and render
acceleration.  The problem is XAA (the acceleration architecture in
Xorg) does not lend it self as well to accelerating these extensions
as KAA (the acceleration architecture in kdrive).  Kdrive accelerates
more of what is needed for composite so composite is faster on Kdrive.

Alex