gentoo-overlay/gnome-extra/gnome-system-monitor/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
<herd>gnome</herd>
<use>
	<flag name="systemd">Display <pkg>sys-apps/systemd</pkg> metadata, e.g.
		unit names, for running processes</flag>
</use>
</pkgmetadata>