[Nouveau] [Bug 100760] Rapid flickering when an app is placed on the second Nouveau ZaphodHeads display

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=100760

m...@advancedcontrols.com.au changed:

   What|Removed |Added

 Resolution|--- |NOTOURBUG
 Status|NEW |RESOLVED

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[Nouveau] [Bug 100760] Rapid flickering when an app is placed on the second Nouveau ZaphodHeads display

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=100760

--- Comment #6 from Ilia Mirkin  ---
Unfortunately I don't have a second monitor here, but I'm fairly sure that your
assertions about multiple X screens not working in recent Xorg is false. People
complain about stuff like that pretty quickly. Unfortunately you chose not to
follow my instructions (never tested putting a regular application on :0.1,
only weird things like gnome-terminal which do who-knows-what in the name of
user friendliness), nor get any help with debugging the issue.

Either way, as you've lost interest in this, can I close the issue?

[The crashes with nouveau are, btw, most likely due to your environment using
3D acceleration. Using such an environment is not recommended.]

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[Nouveau] [Bug 100760] Rapid flickering when an app is placed on the second Nouveau ZaphodHeads display

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=100760

--- Comment #5 from m...@advancedcontrols.com.au ---
Thanks Ilia. I haven't done the ssh test yet, but I've got further data on the
problem:

Under Nouveau my computer started crashing about once a day. (The screens
suddenly go black, and trying to play audio from a known open terminal fails,
so X was probably crashing, and a hardware reset is required, after which the
logs often showed Cron processes doing stuff after the crash, so the Kernel
wasn't crashing.)

A 304xx proprietary Nvidia driver that works on the latest X had since been
released, so I tried that.

Results:

1. My computer is no longer crashing. A potential cause of the crashes under
Nouveau is high GPU idle usage -- the GPU temp is permanently at least 20
degrees C lower under the proprietary driver. My card is a mid-range card with
extensive passive cooling, so fan speed control by Nouveau is no help.

https://forums.opensuse.org/showthread.php/456958-Nouveau-driver-and-GPU-temperature
http://www.phoronix.com/scan.php?page=article=nouveau_comp_2011=19
https://forums.gentoo.org/viewtopic-t-837855-start-0.html

2. The proprietary driver has "Separate X Screen" and "TwinView" modes.
"Separate X Screen" was what I had been using, and this no longer works on the
latest X (the second screen is black, only the pointer appears). So, as
suspected, the loss of "Zaphod" is an X issue rather than a Nouveau issue.
There's no flickering in Mate however, so this _is_ a Nouveau issue.

So I'm currently using TwinView, which is the same as the XRandR Nouveau mode.
I'm still adapting to the loss of separate sets of virtual desktops.

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[Nouveau] [Bug 100760] Rapid flickering when an app is placed on the second Nouveau ZaphodHeads display

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=100760

--- Comment #4 from Ilia Mirkin  ---
If you have a second machine you can ssh in from, I'd recommend taking MATE/etc
out of the equation.

What I mean by that is that on the target machine, start X by just running "X"
on the terminal. This should light up both screens but have a black background
(as the old greyish mask was removed some time back). Then ssh in and run
DISPLAY=:0.1 xterm . If this doesn't work, that means that your second screen
(by which I mean X screen btw) is not set up properly. In such a case, please
provide your xorg log and xorg.conf.

Most people use Zaphod to merge heads from multiple GPUs into a single logical
screen with Xinerama. However I believe at least Mario Kleiner has, in the
past, tested something more akin to your use-case (and helped diagnose/fix
related bugs).

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[Nouveau] [Bug 100760] Rapid flickering when an app is placed on the second Nouveau ZaphodHeads display

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=100760

--- Comment #3 from m...@advancedcontrols.com.au ---
Many thanks Ilia for those helpful suggestions.

The results of the experiments are, that in ZaphodHeads mode:

1. Running "DISPLAY=:0.1 gnome-terminal" under all window managers makes the
terminal display correctly, but on display :0.0.

2. Running "DISPLAY=:0.1 mate-terminal" or "DISPLAY=:0.1 xterm" under Gnome 3,
Gnome Classic, or Gnome on X (rather than Wayland) makes the terminal appear on
display :0.1 without flickering, but there's no window border, and any typing
goes to the original terminal.

3. Running "DISPLAY=:0.1 mate-terminal" or "DISPLAY=:0.1 xterm" under MATE
causes the same as above plus the intense flickering.

So the flickering is a MATE problem, but the inability to use the second
display is an X problem. This matches my experience with the problems starting
under the proprietary driver, with the background image and menus going first,
and later requiring the explicit setting of DISPLAY.

I've found independent virtual desktops such a productive feature, I'm
disappointed it's going away.

I suppose other than the fix-it-myself option you suggest, I could:

1. Try to install an X (and maybe also a MATE) downgrade, such as the one that
was working on F23,

2. Get a new graphics card to see whether that works with twin X-displays on
either Nouveau or the proprietary driver (again the hardware will have
outlasted the software). Is anyone successfully using Zaphod on a current
distro?, or

3. Wait for an X update that fixes this.

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[Nouveau] [Bug 100760] Rapid flickering when an app is placed on the second Nouveau ZaphodHeads display

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=100760

--- Comment #2 from Ilia Mirkin  ---
While Zaphod is considered a legacy feature, that doesn't mean that things
should break. Just that it's unlikely to be extended to support new things.

There has recently been some bugs introduced into xserver which break
non-xrandr setups. There are also some issues in the nouveau driver. One of
those was fixed in xf86-video-nouveau 1.0.15. For the xserver issues, see bug
#100293.

I cannot comment on any bugs that happen in MATE/whatever other software as a
result of multi-screen displays. Note that these are not commonly tested. If
you can do 'DISPLAY=:0.1 xterm', then everything else is down to the X clients.

Please try the above fixes and see if they improve things. If they don't,
you're going to have to debug this, or provide sufficient info for others to
debug it.

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[Nouveau] [Bug 100760] Rapid flickering when an app is placed on the second Nouveau ZaphodHeads display

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=100760

--- Comment #1 from m...@advancedcontrols.com.au ---
Further information:

1. The graphics card is a GeForce 7600 GT (NV4B/G73). Would ZaphodHeads be more
likely to work in a recent card?

2. The working single-X-display mode is using XRandR (I said Xinerama).

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