Comment # 28 on bug 965564 from Thomas Blume

Created attachment 665194 [details]
systemd-obs-defaults-patch

man systemd.resource-control shows:

-->--
TasksAccounting=

Turn on task accounting for this unit. Takes a boolean argument. If enabled,
the system manager will keep track of the number of tasks in the unit. The
number of tasks accounted this way includes both kernel threads and userspace
processes, with each thread counting individually. Note that turning on tasks
accounting for one unit will also implicitly turn it on for all units contained
in the same slice and for all its parent slices and the units contained
therein. The system default for this setting may be controlled with
DefaultTasksAccounting= in systemd-system.conf(5).
--<--

Please try attached patch for the kernel-obs-build package.