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

Daniel Kasak dkasak at nusconsulting.com.au
Mon Jul 30 16:09:11 PDT 2007

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
website: http://www.nusconsulting.com.au

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