The plasmashell process exhibits systemic memory growth; it uses ~4 GiB initially (with less than 10% of that resident), but grows significantly after 24-48 hours grows (most recently, to about 13 GiB; in this case, not much of that was resident, but it was consuming about half my swap). This may be a semi-recent development that has been occurring for a few months now (at least, I don't recall seeing it in early 2017). It is very noticeable because overnight my machine runs out of real memory and runs very slowly as stuff gets swapped back in (often, after killing and restarting plasma). kscreenlocker may also be affected. Some nights, one or the other of these has been OOM-killed. I've tried running under valgrind; the best, not-so-helpful backtrace suggests there may be a GL context leak. To hazard a guess, this *may* be related to using slideshow as wallpaper? Otherwise, I have minimal widgets; just a panel with taskbar, system tray, clock and kdevelop session chooser. My screen locker also uses slideshow.
I am using: bash-4.4.12-12.fc27.x86_64 coreutils-8.27-17.fc27.x86_64 dbus-x11-1.12.0-1.fc27.x86_64 glibc-2.26-21.fc27.x86_64 iso-codes-3.75-2.fc27.noarch kactivitymanagerd-5.11.4-1.fc27.x86_64 kde-settings-plasma-27-1.fc27.noarch kf5-attica-5.41.0-1.fc27.x86_64 kf5-baloo-5.41.0-2.fc27.x86_64 kf5-baloo-libs-5.41.0-2.fc27.x86_64 kf5-filesystem-5.41.0-1.fc27.x86_64 kf5-frameworkintegration-5.41.0-2.fc27.x86_64 kf5-kactivities-libs-5.41.0-1.fc27.x86_64 kf5-kauth-5.41.0-1.fc27.x86_64 kf5-kbookmarks-5.41.0-2.fc27.x86_64 kf5-kcodecs-5.41.0-1.fc27.x86_64 kf5-kcompletion-5.41.0-2.fc27.x86_64 kf5-kconfig-core-5.41.0-1.fc27.x86_64 kf5-kconfig-gui-5.41.0-1.fc27.x86_64 kf5-kconfigwidgets-5.41.0-1.fc27.x86_64 kf5-kcoreaddons-5.41.0-1.fc27.x86_64 kf5-kcrash-5.41.0-1.fc27.x86_64 kf5-kdbusaddons-5.41.0-1.fc27.x86_64 kf5-kdeclarative-5.41.0-1.fc27.x86_64 kf5-kded-5.41.0-2.fc27.x86_64 kf5-kdelibs4support-libs-5.41.0-1.fc27.x86_64 kf5-kdoctools-5.41.0-1.fc27.x86_64 kf5-kfilemetadata-5.41.0-1.fc27.x86_64 kf5-kglobalaccel-5.41.0-1.fc27.x86_64 kf5-kglobalaccel-libs-5.41.0-1.fc27.x86_64 kf5-kguiaddons-5.41.0-1.fc27.x86_64 kf5-ki18n-5.41.0-1.fc27.x86_64 kf5-kiconthemes-5.41.0-1.fc27.x86_64 kf5-kinit-5.41.0-1.fc27.x86_64 kf5-kio-core-libs-5.41.0-3.fc27.x86_64 kf5-kio-file-widgets-5.41.0-3.fc27.x86_64 kf5-kio-widgets-libs-5.41.0-3.fc27.x86_64 kf5-kitemmodels-5.41.0-1.fc27.x86_64 kf5-kitemviews-5.41.0-1.fc27.x86_64 kf5-kjobwidgets-5.41.0-1.fc27.x86_64 kf5-knewstuff-5.41.0-1.fc27.x86_64 kf5-knotifications-5.41.0-1.fc27.x86_64 kf5-kpackage-5.41.0-1.fc27.x86_64 kf5-kparts-5.41.0-1.fc27.x86_64 kf5-krunner-5.41.0-1.fc27.x86_64 kf5-kservice-5.41.0-1.fc27.x86_64 kf5-ktexteditor-5.41.0-2.fc27.x86_64 kf5-ktextwidgets-5.41.0-1.fc27.x86_64 kf5-kunitconversion-5.41.0-1.fc27.x86_64 kf5-kwayland-5.41.0-1.fc27.x86_64 kf5-kwidgetsaddons-5.41.0-1.fc27.x86_64 kf5-kwindowsystem-5.41.0-1.fc27.x86_64 kf5-kxmlgui-5.41.0-1.fc27.x86_64 kf5-kxmlrpcclient-5.41.0-1.fc27.x86_64 kf5-plasma-5.41.0-1.fc27.x86_64 kf5-prison-5.41.0-1.fc27.x86_64 kf5-solid-libs-5.41.0-1.fc27.x86_64 kf5-sonnet-ui-5.41.0-1.fc27.x86_64 khotkeys-5.11.4-1.fc27.x86_64 kscreenlocker-5.11.4-1.fc27.x86_64 ksysguardd-5.11.4-1.fc27.x86_64 libICE-1.0.9-11.fc27.x86_64 libSM-1.2.2-7.fc27.x86_64 libX11-1.6.5-4.fc27.x86_64 libXext-1.3.3-7.fc27.x86_64 libXrender-0.9.10-4.fc27.x86_64 libXtst-1.2.3-4.fc27.x86_64 libgcc-7.2.1-2.fc27.x86_64 libksysguard-5.11.4-1.fc27.x86_64 libkworkspace5-5.11.4-1.fc27.x86_64 libstdc++-7.2.1-2.fc27.x86_64 libxcb-1.12-5.fc27.x86_64 oxygen-sound-theme-5.11.4-1.fc27.noarch phonon-qt5-4.9.1-5.fc27.x86_64 plasma-desktop-5.11.4-1.fc27.x86_64 plasma-lookandfeel-fedora-5.11.4-1.fc27.noarch plasma-milou-5.11.4-1.fc27.x86_64 plasma-pa-5.11.4-1.fc27.x86_64 plasma-workspace-5.11.4-1.fc27.x86_64 plasma-workspace-common-5.11.4-1.fc27.x86_64 plasma-workspace-libs-5.11.4-1.fc27.x86_64 polkit-kde-5.11.4-1.fc27.x86_64 powerdevil-5.11.4-1.fc27.x86_64 qt5-qtbase-5.9.2-6.fc27.x86_64 qt5-qtbase-gui-5.9.2-6.fc27.x86_64 qt5-qtdeclarative-5.9.2-2.fc27.x86_64 qt5-qtgraphicaleffects-5.9.2-1.fc27.x86_64 qt5-qtquickcontrols-5.9.2-1.fc27.x86_64 qt5-qtscript-5.9.2-1.fc27.x86_64 qt5-qttools-5.9.2-1.fc27.x86_64 qt5-qtx11extras-5.9.2-1.fc27.x86_64 socat-1.7.3.2-4.fc27.x86_64 systemd-234-9.fc27.x86_64 xcb-util-0.4.0-8.fc27.x86_64 xcb-util-image-0.4.0-8.fc27.x86_64 xorg-x11-apps-7.7-18.fc27.x86_64 xorg-x11-server-utils-7.7-23.fc27.x86_64 xorg-x11-utils-7.5-25.fc27.x86_64 zlib-1.2.11-4.fc27.x86_64
*** This bug has been marked as a duplicate of bug 368838 ***
Still occurs with: bash-4.4.19-1.fc27.x86_64 coreutils-8.27-20.fc27.x86_64 dbus-x11-1.12.0-1.fc27.x86_64 glibc-2.26-24.fc27.x86_64 iso-codes-3.75-2.fc27.noarch kactivitymanagerd-5.11.5-1.fc27.x86_64 kde-settings-plasma-27-1.fc27.noarch kf5-attica-5.42.0-1.fc27.x86_64 kf5-baloo-5.42.0-1.fc27.x86_64 kf5-baloo-libs-5.42.0-1.fc27.x86_64 kf5-filesystem-5.42.0-2.fc27.x86_64 kf5-frameworkintegration-5.42.0-2.fc27.x86_64 kf5-kactivities-libs-5.42.0-1.fc27.x86_64 kf5-kauth-5.42.0-2.fc27.x86_64 kf5-kbookmarks-5.42.0-1.fc27.x86_64 kf5-kcodecs-5.42.0-1.fc27.x86_64 kf5-kcompletion-5.42.0-1.fc27.x86_64 kf5-kconfig-core-5.42.0-1.fc27.x86_64 kf5-kconfig-gui-5.42.0-1.fc27.x86_64 kf5-kconfigwidgets-5.42.0-1.fc27.x86_64 kf5-kcoreaddons-5.42.0-1.fc27.x86_64 kf5-kcrash-5.42.0-1.fc27.x86_64 kf5-kdbusaddons-5.42.0-1.fc27.x86_64 kf5-kdeclarative-5.42.0-2.fc27.x86_64 kf5-kded-5.42.0-1.fc27.x86_64 kf5-kdelibs4support-libs-5.42.0-1.fc27.x86_64 kf5-kdoctools-5.42.0-1.fc27.x86_64 kf5-kfilemetadata-5.42.0-1.fc27.x86_64 kf5-kglobalaccel-5.42.0-1.fc27.x86_64 kf5-kglobalaccel-libs-5.42.0-1.fc27.x86_64 kf5-kguiaddons-5.42.0-1.fc27.x86_64 kf5-ki18n-5.42.0-1.fc27.x86_64 kf5-kiconthemes-5.42.0-1.fc27.x86_64 kf5-kinit-5.42.0-1.fc27.x86_64 kf5-kio-core-libs-5.42.0-1.fc27.x86_64 kf5-kio-file-widgets-5.42.0-1.fc27.x86_64 kf5-kio-widgets-libs-5.42.0-1.fc27.x86_64 kf5-kitemmodels-5.42.0-1.fc27.x86_64 kf5-kitemviews-5.42.0-1.fc27.x86_64 kf5-kjobwidgets-5.42.0-1.fc27.x86_64 kf5-knewstuff-5.42.0-1.fc27.x86_64 kf5-knotifications-5.42.0-1.fc27.x86_64 kf5-kpackage-5.42.0-1.fc27.x86_64 kf5-kparts-5.42.0-1.fc27.x86_64 kf5-krunner-5.42.0-1.fc27.x86_64 kf5-kservice-5.42.0-1.fc27.x86_64 kf5-ktexteditor-5.42.0-1.fc27.x86_64 kf5-ktextwidgets-5.42.0-1.fc27.x86_64 kf5-kunitconversion-5.42.0-1.fc27.x86_64 kf5-kwayland-5.42.0-2.fc27.x86_64 kf5-kwidgetsaddons-5.42.1-1.fc27.x86_64 kf5-kwindowsystem-5.42.0-1.fc27.x86_64 kf5-kxmlgui-5.42.0-1.fc27.x86_64 kf5-kxmlrpcclient-5.42.0-1.fc27.x86_64 kf5-plasma-5.42.0-1.fc27.x86_64 kf5-prison-5.42.0-1.fc27.x86_64 kf5-solid-libs-5.42.0-1.fc27.x86_64 kf5-sonnet-ui-5.42.0-1.fc27.x86_64 khotkeys-5.11.5-1.fc27.x86_64 kscreenlocker-5.11.5-1.fc27.x86_64 ksysguardd-5.11.5-1.fc27.x86_64 libICE-1.0.9-11.fc27.x86_64 libSM-1.2.2-7.fc27.x86_64 libX11-1.6.5-4.fc27.x86_64 libXext-1.3.3-7.fc27.x86_64 libXrender-0.9.10-4.fc27.x86_64 libXtst-1.2.3-4.fc27.x86_64 libgcc-7.3.1-2.fc27.x86_64 libksysguard-5.11.5-1.fc27.x86_64 libkworkspace5-5.11.5-3.fc27.x86_64 libstdc++-7.3.1-2.fc27.x86_64 libxcb-1.12-5.fc27.x86_64 oxygen-sound-theme-5.11.5-1.fc27.noarch phonon-qt5-4.9.1-5.fc27.x86_64 plasma-desktop-5.11.5-1.fc27.x86_64 plasma-lookandfeel-fedora-5.11.5-3.fc27.noarch plasma-milou-5.11.5-1.fc27.x86_64 plasma-pa-5.11.5-1.fc27.x86_64 plasma-workspace-5.11.5-3.fc27.x86_64 plasma-workspace-common-5.11.5-3.fc27.x86_64 plasma-workspace-libs-5.11.5-3.fc27.x86_64 polkit-kde-5.11.5-1.fc27.x86_64 powerdevil-5.11.5-1.fc27.x86_64 qt5-qtbase-5.9.4-1.fc27.x86_64 qt5-qtbase-gui-5.9.4-1.fc27.x86_64 qt5-qtdeclarative-5.9.4-1.fc27.x86_64 qt5-qtgraphicaleffects-5.9.4-1.fc27.x86_64 qt5-qtquickcontrols-5.9.4-1.fc27.x86_64 qt5-qtscript-5.9.4-1.fc27.x86_64 qt5-qttools-5.9.4-1.fc27.x86_64 qt5-qtx11extras-5.9.4-1.fc27.x86_64 socat-1.7.3.2-4.fc27.x86_64 systemd-234-9.fc27.x86_64 xcb-util-0.4.0-8.fc27.x86_64 xcb-util-image-0.4.0-8.fc27.x86_64 xorg-x11-apps-7.7-18.fc27.x86_64 xorg-x11-server-utils-7.7-23.fc27.x86_64 xorg-x11-utils-7.5-25.fc27.x86_64 zlib-1.2.11-4.fc27.x86_64