systemd: assign real-time budget

systemd/mpd.service.in

@@ -5,5 +5,18 @@ After=network.target sound.target
 [Service]
 ExecStart=@prefix@/bin/mpd --no-daemon
 
+# allow MPD to use real-time priority 50
+LimitRTPRIO=50
+LimitRTTIME=-1
+
+# move MPD to a top-level cgroup, as real-time budget assignment fails
+# in cgroup /system/mpd.service, because /system has a zero real-time
+# budget; see
+# http://www.freedesktop.org/wiki/Software/systemd/MyServiceCantGetRealtime/
+ControlGroup=cpu:/mpd
+
+# assign a real-time budget
+ControlGroupAttribute=cpu.rt_runtime_us 500000
+
 [Install]
 WantedBy=multi-user.target