On my iMac, before the last kernel upgrade, everything ran reasonably fine. With the latest kernel, this bug slipped in: https://bugs.freedesktop.org/show_bug.cgi?id=57350
It manifests by showing broken cursors in X and logfiles filling in with error messages containing - more or less:
Jan 22 17:17:40 iMac kernel: [ 1112.319783] nouveau E[ PFB][0000:03:00.0] trapped read at 0x00008ef264 on channel 0x0000fee0 BAR/PFIFO_READ/FB reason: PAGE_NOT_PRESENT
The word is that putting the system to sleep and waking it up again at least stops the bug from filling up the hard-disk with error logs. It does seem to work on my machine here that way.
Does anyone know a better fix?
Option "HWCursor" "False"
in a config file (in /etc/X11/xorg.conf.d/) help, as suggested here ?