[root@localhost ~]# cat /etc/tmpfiles.d/swappiness.conf
w	/sys/fs/cgroup/memory/system.slice/memory.swappiness	-	-	-	-	10
w	/sys/fs/cgroup/memory/user.slice/memory.swappiness	-	-	-	-	10
w	/sys/fs/cgroup/memory/init.scope/memory.swappiness	-	-	-	-	10

[root@localhost ~]# cat $(find /sys/fs/cgroup/memory -name memory.swappiness) | sort -n | uniq -c
     67 10   // some got the '10'
      1 30   // global cgroup
     45 60   // some still at default