Nvidia Driver Perfomance Xgl Vs Aiglx

Although the testing is purely subjective and anecdotal, back to back installations of compiz-fusion (under Gnome) with Xgl and again with AIGLX indicate that with at least the current driver from nVidia, there's more overhead with Xgl thnat AIGLX. On a desktop system with a 2.4GHz P4 and 1G memory, and an nVidia GeForce 6200 video card, OpenGL-based screensaver hacks ran poorly, with objects moving in bursts or jerks. Block tube, for example, didn't spin smoothly, and the flying toasters lurched along in their flight paths. Using either gears or aquarium in the cube brought the system almost completely to its knees, particularly the aquarium (even with limited numbers of fish). With AIGLX, however, sceensaver hacks move smoothly, even with gears spinning away inside the cube. A full-on aquarium population is still a challenge of sorts but I'll live without that somehow...

XGL will certainly add overhead, since you're effectively running a nested X server within the XGL server.

But the real issue with that approach is that since the XGL server "owns" the access to the graphical interface, the nested server (the one you're really using for your desktop) cannot see or access the hardware adapter directly, it assumes you do not have hardware acceleration available and falls back to using software libraries for openGL rendering.

If you use an app that is "XGL-aware", then it can take advantage of hardware acceleration, but right now compiz is pretty much the only app that does. Any other standard X based GL apps will be unable to utilize hardware acceleration under XGL, which means you take a substantial performance hit when running 3d apps on your 3d desktop. The one advantage that XGL offers is that by implementing compositing transparently, it will work with almost any 3d-capable hardware without requiring special support built into the driver (as in AIGLX).

AIGLX permits the compositing to be supported directly by the driver, rather than requiring an extra layer like XGL that interferes with other apps being able to utilize hardware acceleration. It's still a relatively new technology, and driver support is still a bit hit and miss depending on the adapter, particularly if you're using ATI, but for the most part this is the direction the technology is heading. KDE4, for instance, didn't even bother building in XGL support for their standard compositing.

So you're totally correct, but the performance is a limitation of the design of XGL. It's a feature, not a bug...

Hope this all makes sense...

Cheers,
KV

Good on ya! I posted the comment in hopes of some input on why I observed what I did. Thanks for enlightenment!

Thanks for enlightenment!
[/b]

You'll find I never resist the opportunity to enlighten, whether you want it or not...

Seriously though, you made an interesting post, particularly since you qualified many of the quirks people run into with XGL, rather than just saying "it runs slower". I know that the distinction between XGL and AIGLX is still vague in a general sense, so hopefully between us, we'll have helped clear it up for others that may be wondering...

Good stuff.

Cheers,
KV

What does 10.3 KDE use by default? XGL is installed per Yast. I have uninstalled anything Compiz related. If I uninstall XGL, and it is being used, will opensuse fall back on AIGLX and work without any problems?

No, openSUSE 10.3 has no built-in provision for AIGLX support. In fact, I don't think the version of compiz that comes with 10.3 will even support it, that was added by the community via beryl, and then remerged in as part of compiz-fusion but you'll need to use the openSUSE build service to obtain the updated packages.

The openSUSE wiki has fairly detailed step by step info if you're looking at using compiz-fusion.

Cheers,
KV

I removed compiz. I don't use it. I was wondering what would happen if I removed XGL. Will opensuse default to AIGLX, or will I have a broken xorg when I reboot? I used AIGLX with Kubuntu because XGL not supporting other 3D apps. I am able to run brutal chess, and other 3D games, so I assume even though XGL is installed, it's not being used? I just wanted to know how to try AIGLX(if I'm not already) on KDE to see if it would run any better.

As I said above, openSUSE won't fall back to AIGLX after you remove XGL. You'll have to configure xorg.conf appropriately. But as long as you do that, and select compiz-fusion from the repos rather than the 10.3-core version of compiz, you'll be fine. And if you don't use compiz anyways, there's no issue. XGL and AIGLX aren't relevant if you're using a standard desktop, and there is no benefit from either with a standard desktop.

I understand where you're coming from, particularly since distros like Kubuntu were flexible enough to handle both types of compositing. Frankly I was a little surprised that 10.3 didn't have built-in support for AIGLX, but at the same time, XGL was Novell-spawned and at the time, the compiz-fusion didn't exist, so with a choice between using the version of compiz that Novell developed and supported in-house (as well as relying exclusively on XGL) versus the flaky-at-that-point-in-time community fork, it sort of makes sense.

The instructions on the wiki make it fairly painless, and cyberorg has done a fantastic job of packaging the latest stable versions of compiz-fusion for openSUSE, so that's your best route to go if you're looking for non-XGL wobbly-window goodness...

If you don't want compiz window enhancements, then it really doesn't matter either way.

Hope this helps?

Cheers,
KV

Any sense of where things are headed in openSUSE 11.0 as far as Xgl / AIGLX go? Or compiz, for that matter?

If the only benefit from using either of them is compiz, I'll just leave it alone. Thanks for clearing that up.