--- a/src/hotspot/share/gc/shenandoah/shenandoahControlThread.cpp	Sat Jan 19 11:19:55 2019 +0100
+++ b/src/hotspot/share/gc/shenandoah/shenandoahControlThread.cpp	Sat Jan 19 11:20:01 2019 +0100
@@ -47,7 +47,7 @@
   _degen_point(ShenandoahHeap::_degenerated_outside_cycle),
   _allocs_seen(0) {
 
-  create_and_start();
+  create_and_start(ShenandoahCriticalControlThreadPriority ? CriticalPriority : NearMaxPriority);
   _periodic_task.enroll();
   _periodic_satb_flush_task.enroll();
 }