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davidm
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PostPosted: Tue Aug 18, 2015 4:53 pm    Post subject: [Info only] Plasma 5 and Nouveau Reply with quote

Just to warn people using Nouveau who are considering upgrading to KDE Plasma 5:

There is a pretty nasty screen and graphics corruption issue present. Mostly it seems it is in the legacy hardware such as Nvidia 8400GS and Nvidia 9500GT (as well as probably other Nvidia GPUs around this era). It will cause pretty nasty corruption of the plasmashell menus (including the tooltips - if you try to work through this it is usually best to turn the tooltips off in systemsettings5) and will sometimes cause hangs of up to two minutes. Occasionally it will cause a full crash.

When present you will see things like this in dmesg:

Code:

[174123.172309] nouveau E[plasmashell[14050]] fail set_domain
[174123.172314] nouveau E[plasmashell[14050]] validating bo list
[174123.172323] nouveau E[plasmashell[14050]] validate: -22
[174123.223066] nouveau E[plasmashell[14050]] fail set_domain
[174123.223070] nouveau E[plasmashell[14050]] validating bo list
[174123.223073] nouveau E[plasmashell[14050]] validate: -22
[174123.470096] nouveau E[     PFB][0000:02:00.0] trapped read at 0x3d00718400 on channel 0x0000f4d2 [plasmashell[14050]] PGRAPH/TEXTURE/00 reason: PT_NOT_PRESENT
[174123.494669] nouveau E[     PFB][0000:02:00.0] trapped read at 0x3d00718400 on channel 0x0000f4d2 [plasmashell[14050]] PGRAPH/TEXTURE/00 reason: PT_NOT_PRESENT


The problem is almost certainly upstream with nouveau/mesa although it's possible it is with Plasma as well as that seems to be where it is triggered mostly.

You may want to track these bugs before making the leap or if you are seeing it:

https://bugs.freedesktop.org/show_bug.cgi?id=91125
https://bugs.freedesktop.org/show_bug.cgi?id=91598

To recover without a reboot you can kill plasmashell (e.g. kill -9) and restart it. You can also just close applications and/or possibly just clear the memory cache with 'echo 1 > /proc/sys/vm/drop_caches' as this works for me to restore proper display. A Nouveau developer suggested it is tied in with running out of vram and mesa not being able to handle this correctly.

I almost tossed my GPU over this thinking it was failing...
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davidm
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Joined: 26 Apr 2009
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PostPosted: Tue Oct 20, 2015 2:13 pm    Post subject: Reply with quote

Just wanted to share that there finally seems to be a working patch for this that helps quite a bit:

https://bugs.freedesktop.org/show_bug.cgi?id=91598#c14

Also since my first post I learned the issue still occurs with kde4 but not as bad. In any event for anyone who runs into this nasty bug the kernel patch above seems to help quite a bit so far in my testing.
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