If I boot kernel-3.11.0-0.rc0.git7.1.fc20.x86_64 or kernel-3.11.0-0.rc1.git1.1.fc20.x86_64 - both of which have debugging symbols enabled (and I boot with slub_debug=-) - throughout my GNOME session I see constant artifacting, describable more or less as bits of the display 'disappearing' (I can see what's behind them, or the desktop) and then showing up again a few seconds later. If I boot kernel-3.11.0-0.rc1.git0.1.fc20.x86_64 - which has debugging symbols disabled - I do not see this artifacting at all. I don't see anything in journalctl that looks related, at a glance. My video adapter is a 01:00.0 VGA compatible controller [0300]: NVIDIA Corporation G94 [GeForce 9600 GT] [10de:0622] (rev a1) , using nouveau. I'll attach a video showing the issue.
Interestingly, the artifacting stops happening if I turn on the Shell screen recorder - not just that it doesn't show up in the video (which I was half expecting), but it actually _stops happening_. I'll try and get a video from my camera.
http://www.happyassassin.net/extras/debug_artifact.mp4 is a video from my camera showing some of the artifacting. Note I have two monitors, the video only shows the right hand one - the panel's on the other, if you're wondering where it is. I'm just typing in xchat and alt-tabbing to Firefox, you can see various artifacts going on.
With 3.11.0-0.rc5.git6.1.fc20.x86_64 the exact corruption described in the OP is not visible any more, but windows tend to flash when I'm switching between them, opening a new one or going to the overview. Still doesn't happen with non-debug kernels.
Reported upstream: https://bugs.freedesktop.org/show_bug.cgi?id=68453
This bug appears to have been reported against 'rawhide' during the Fedora 20 development cycle. Changing version to '20'. More information and reason for this action is here: https://fedoraproject.org/wiki/BugZappers/HouseKeeping/Fedora20
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Fedora 20 changed to end-of-life (EOL) status on 2015-06-23. Fedora 20 is no longer maintained, which means that it will not receive any further security or bug fix updates. As a result we are closing this bug. If you can reproduce this bug against a currently maintained version of Fedora please feel free to reopen this bug against that version. If you are unable to reopen this bug, please file a new report against the current release. If you experience problems, please add a comment to this bug. Thank you for reporting this bug and we are sorry it could not be fixed.