Created attachment 811016 [details]
syslog, output of ipcs -m, ipcs -mp, ipcs -mt, and ps aux - packed as tgz

I have OpenSUSE Leap 15.1 installed with KDE / plasmashell with latest (stable)
versions available, relevant version numbers:
xorg-x11-server-1.20.3-lp151.3.1.x86_64
sddm-0.18.0-lp151.2.2.x86_64
libQt5Core5-5.9.7-lp151.3.1.x86_64
libQt5Gui5-5.9.7-lp151.3.1.x86_64
plasma5-session-5.12.8-lp151.2.1.noarch

I am using a dual-screen setup. Whenever you leave the login screen (SDDM login
manager) idle for some time, the system starts consuming (shared) memory. It
starts with ~23 shared memory segments, which steadly increase with time (see
my attachments). A successful login or a restart of the display-manager
(systemctl restart display-manager) "resets" the shared memory usage.
After 18 hours of idling, 20 GB of my overall 32 GB Ram is used by these shared
memory segments. Is the current X-Server still using shared memory transport ?
That's where I would suspect the bug, although I believe this must be a special
case - because even though I searched thoroughly, I couldn't find anything
related...

Let me know if I can post any more information which helps to pin down the
problem.

Cheers,
Martin Renwanz