[PATCH] Ensure blitter quiescience before reading pixels from the framebuffer

[Daniel Kasak]

On Mon, 2007-07-30 at 19:02 +0200, Michel Dänzer wrote:

> Not sure there's still anyone around who cares about XAA...

As others have noted, XAA is all we've got at present. Having said that,
I appreciate that work is going on with EXA. In particular the zero-copy
GLX_EXT_texture_from_pixmap stuff for my r300 does wonders for beryl /
compiz, and I'm certainly grateful for this and any other work done, but
in all honesty, this is a corner case ( albeit a very nice looking
one ). While it makes compiz smoother, it ( EXA ) also slows down actual
rendering of apps by an order of magnitude. Sure, a compositing manager
on top of this largely hides this fact, but compiz is still
experimental, and I'm certainly not rolling it out as the standard
desktop any time soon.

> > On xf86-video-intel 2.1.0 with Beryl / Emerald drawing everying, XAA is still way
> > faster then EXA. Noticable - like 5x faster w/ EXA on a Core 2 Duo MacBook.

I've found this too, and not just with a composited desktop. Running
Enlightenment with the XRENDER backend and EXA gives me about 1 fps with
100% CPU load with relatively mildly animated backgrounds ( I845G
video ) - which run effortlessly at 30fps and low CPU load otherwise.
Unfortunately the fastest method with E17 is still the software
renderer, which seems quite counter-intuitive. Also tested with r300
( but of course the r300 driver notes that it doesn't accelerate XRENDER
to start with ).

> > On my girl's Sony Vaio with just a Core Duo @ 1.66 GHz the same Intel driver
> > (just built for 32bit of course) is so slow, that it just draws 1fps with EXA when
> > you scroll in kpdf, abiword etc. while with EXA it is usable, most of the time.
> 
> For a GLX compositing manager, you need zero-copy
> GLX_EXT_texture_from_pixmap which is only available in the xserver GIT
> master branch (and only with the Mesa GIT master branch driver i915tex
> for this hardware so far).

I've also been trying to get this working. If I set the Legacy3D option
to 'false', I get:

no GLXFBConfig for default depth
this isn't going to work ...

I've tried this with 15bit, 16bit and 24bit colour. Commenting out the
Legacy3D 'false' line allows me to run compiz.

--
Daniel Kasak
IT Developer
NUS Consulting Group
Level 5, 77 Pacific Highway
North Sydney, NSW, Australia 2060
T: (+61) 2 9922-7676 / F: (+61) 2 9922 7989
email: dkasak at nusconsulting.com.au
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