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How is gnome's failsafe mode different from its default mode?

Asked by Joe Blaylock

I've just upgraded from Feisty to Hardy, and now my 3d performance is awful. But, if I log into gnome in the gnome failsafe mode, it works fine. So, what's different between gnome's failsafe mode and gnome's default mode, and what do I frob on the system to make the default mode not stomp on Xgl?

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Brewster Malevich (brews) said : 		#1

Try turning off the visual effects (compiz): 'System' => 'Preferences' => 'Appearances'. Alot of graphics cards have trouble when compiz is used, but then run well when it's turned off. How are you testing your visual performance? What graphics card do you have?

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Joe Blaylock (jrbl) said : 		#2

It's an IBM Thinkpad T41, with an ATI Radeon Mobility M7. When I log in in failsafe mode, I can run:
$ glxinfo | grep direct
and get the "Yes" that I'm looking for.

I can also run glxgears and get about 700 fps, which while not great, is better than software emulation. Also, there are no artifacts on the display. And the running X server is Xgl.

When I log in in any other mode, running glxinfo says that it's Software Indirect. glxgears gives about 60 fps, and the running X server is Xorg.

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Joe Blaylock (jrbl) said : 		#3

So it still seems to me like there's something fundamentally different between GNOME Failsafe and GNOME logins, and I'd like to know what that is, and how to make the GNOME login behave like the Failsafe one (so I don't have to log in to failsafe all the time.)

Update on the previous: Also, when I'm logged into GNOME with the Xorg server, compiz causes a lot of visible artifacts on the screen, a lot of corruption. Which I guess is expected, but still annoying.

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Best Sam_ (and-sam) said : 		#4

Hi,
first of all, 3D is not compiz, 3D acceleration doesn't mean that compiz is functioning well.
Also in Hardy compiz is now the compositing from metacity, because metacity provides a light form of compositing and the real compiz calls compiz.real.
If compiz.real is running the compositing of metacity should be turned off, see gconf/apps/metacity/general/compositing_manager.

You didn't mention which driver is in use. Blacklisted drivers are listed in usr/bin/compiz, which can be opened with e.g. #sudo gedit usr/bin/compiz
It could be that in failsafe mode a different configuration is in use. Reading Xorg.0.log could help or
starting in the terminal
#compiz.real --replace; compiz
should provide messages what's going on.

From my view xserver-xgl isn't state of the art anymore, so to speak.
You can look in the Xorg.0.log if AIGLX is enabled.
Some interesting information on that is in Bug #136598
quote John Dong
>>Xgl accelerates 3D indirectly, but it is still accelerated. Direct rendering != 3D support<<

So it might help to remove the package xserver-xgl.

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Joe Blaylock (jrbl) said : 		#5

Sam: Thanks. There wasn't anything useful in the Xorg logs; I couldn't find any difference from run to the other, except that DRI was disabled. BUT! Doing an apt-get remove xserver-xgl made my problems go away. DRI is consistently enabled now, and I can't tell the difference between a GNOME Failsafe and a regular GNOME login any more. So, I still don't really understand why it was broken, which bothers me, but it's not broken any more, which satisfies me. Thank you.

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Joe Blaylock (jrbl) said : 		#6

Thanks Sam, that solved my question.

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Sam_ (and-sam) said : 		#7

That's fine Joe.
Just want to add, in this script #usr/bin/compiz, line #360 it says #Don't use compiz when running the failsafe session.