The only workaround I can find for now is to start LibreOffice with the following environment variable (or add it to /etc/environment): SAL_USE_VCLPLUGIN=gen libreoffice The other options (SAL_USE_VCLPLUGIN=kde4 | SAL_USE_VCLPLUGIN=gtk | SAL_USE_VCLPLUGIN=gtk3) all cause the high CPU usage. So it definitely has something to do with the desktop environment integration.