I initially posed this as Question #188982, but now decided to report it as it seems to persist and no definitive answers as to the cause were found. I was apprehensive about reporting at first mainly because this doesn’t seem to occur on my other (Precise-running) computers. It is however 100% reproducible on this one (i.e. the flood occurs on each creation of an Xorg log, though I don’t know what triggers individual lines).

My Xorg log is flooded with lines about reusing xkmfile:

jani@saegusa:~$ grep ”XKB: reuse xkmfile /var/lib/xkb/server-” /var/log/Xorg.0.log | tail
[ 391.894] (II) XKB: reuse xkmfile /var/lib/xkb/server-5CBD5B10CEC815928ACEFB86BAB14051BA0C83FF.xkm
[ 391.901] (II) XKB: reuse xkmfile /var/lib/xkb/server-5CBD5B10CEC815928ACEFB86BAB14051BA0C83FF.xkm
[ 391.906] (II) XKB: reuse xkmfile /var/lib/xkb/server-5CBD5B10CEC815928ACEFB86BAB14051BA0C83FF.xkm
[ 391.909] (II) XKB: reuse xkmfile /var/lib/xkb/server-5CBD5B10CEC815928ACEFB86BAB14051BA0C83FF.xkm
[ 391.914] (II) XKB: reuse xkmfile /var/lib/xkb/server-5CBD5B10CEC815928ACEFB86BAB14051BA0C83FF.xkm
[ 391.919] (II) XKB: reuse xkmfile /var/lib/xkb/server-5CBD5B10CEC815928ACEFB86BAB14051BA0C83FF.xkm
[ 391.922] (II) XKB: reuse xkmfile /var/lib/xkb/server-5CBD5B10CEC815928ACEFB86BAB14051BA0C83FF.xkm
[ 391.926] (II) XKB: reuse xkmfile /var/lib/xkb/server-5CBD5B10CEC815928ACEFB86BAB14051BA0C83FF.xkm
[ 391.929] (II) XKB: reuse xkmfile /var/lib/xkb/server-5CBD5B10CEC815928ACEFB86BAB14051BA0C83FF.xkm
[ 391.933] (II) XKB: reuse xkmfile /var/lib/xkb/server-5CBD5B10CEC815928ACEFB86BAB14051BA0C83FF.xkm
jani@saegusa:~$ grep ”XKB: reuse xkmfile /var/lib/xkb/server-” /var/log/Xorg.0.log | wc -l
1507

(Interestingly I now notice that the number of those lines seems to be constant: the above was copy+paste from terminal just now, and when I posed Question #188982 on 2012-02-27, the result was 1507 also.)