--- a/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp	Tue May 21 10:34:57 2019 +0200
+++ b/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp	Tue May 21 10:36:23 2019 +0200
@@ -30,6 +30,7 @@
 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
 #include "gc/shenandoah/shenandoahTraversalGC.hpp"
 #include "gc/shared/space.inline.hpp"
+#include "jfr/jfrEvents.hpp"
 #include "memory/iterator.inline.hpp"
 #include "memory/resourceArea.hpp"
 #include "memory/universe.hpp"
@@ -93,7 +94,7 @@
     case _empty_uncommitted:
       do_commit();
     case _empty_committed:
-      _state = _regular;
+      set_state(_regular);
     case _regular:
     case _pinned:
       return;
@@ -114,10 +115,10 @@
     case _cset:
     case _humongous_start:
     case _humongous_cont:
-      _state = _regular;
+      set_state(_regular);
       return;
     case _pinned_cset:
-      _state = _pinned;
+      set_state(_pinned);
       return;
     case _regular:
     case _pinned:
@@ -133,7 +134,7 @@
     case _empty_uncommitted:
       do_commit();
     case _empty_committed:
-      _state = _humongous_start;
+      set_state(_humongous_start);
       return;
     default:
       report_illegal_transition("humongous start allocation");
@@ -149,7 +150,7 @@
     case _regular:
     case _humongous_start:
     case _humongous_cont:
-      _state = _humongous_start;
+      set_state(_humongous_start);
       return;
     default:
       report_illegal_transition("humongous start bypass");
@@ -162,7 +163,7 @@
     case _empty_uncommitted:
       do_commit();
     case _empty_committed:
-      _state = _humongous_cont;
+     set_state(_humongous_cont);
       return;
     default:
       report_illegal_transition("humongous continuation allocation");
@@ -178,7 +179,7 @@
     case _regular:
     case _humongous_start:
     case _humongous_cont:
-      _state = _humongous_cont;
+      set_state(_humongous_cont);
       return;
     default:
       report_illegal_transition("humongous continuation bypass");
@@ -190,14 +191,14 @@
   switch (_state) {
     case _regular:
       assert (_critical_pins == 0, "sanity");
-      _state = _pinned;
+      set_state(_pinned);
     case _pinned_cset:
     case _pinned:
       _critical_pins++;
       return;
     case _humongous_start:
       assert (_critical_pins == 0, "sanity");
-      _state = _pinned_humongous_start;
+      set_state(_pinned_humongous_start);
     case _pinned_humongous_start:
       _critical_pins++;
       return;
@@ -219,7 +220,7 @@
       assert (_critical_pins > 0, "sanity");
       _critical_pins--;
       if (_critical_pins == 0) {
-        _state = _regular;
+        set_state(_regular);
       }
       return;
     case _regular:
@@ -231,14 +232,14 @@
       assert (_critical_pins > 0, "sanity");
       _critical_pins--;
       if (_critical_pins == 0) {
-        _state = _cset;
+        set_state(_cset);
       }
       return;
     case _pinned_humongous_start:
       assert (_critical_pins > 0, "sanity");
       _critical_pins--;
       if (_critical_pins == 0) {
-        _state = _humongous_start;
+        set_state(_humongous_start);
       }
       return;
     default:
@@ -250,7 +251,7 @@
   _heap->assert_heaplock_owned_by_current_thread();
   switch (_state) {
     case _regular:
-      _state = _cset;
+      set_state(_cset);
     case _cset:
       return;
     default:
@@ -268,7 +269,7 @@
       // Reclaiming humongous regions
     case _regular:
       // Immediate region reclaim
-      _state = _trash;
+      set_state(_trash);
       return;
     default:
       report_illegal_transition("trashing");
@@ -287,7 +288,7 @@
   _heap->assert_heaplock_owned_by_current_thread();
   switch (_state) {
     case _trash:
-      _state = _empty_committed;
+      set_state(_empty_committed);
       _empty_time = os::elapsedTime();
       return;
     default:
@@ -300,7 +301,7 @@
   switch (_state) {
     case _empty_committed:
       do_uncommit();
-      _state = _empty_uncommitted;
+      set_state(_empty_uncommitted);
       return;
     default:
       report_illegal_transition("uncommiting");
@@ -314,7 +315,7 @@
   switch (_state) {
     case _empty_uncommitted:
       do_commit();
-      _state = _empty_committed;
+      set_state(_empty_committed);
       return;
     default:
       report_illegal_transition("commit bypass");
@@ -679,3 +680,16 @@
   }
   _heap->decrease_committed(ShenandoahHeapRegion::region_size_bytes());
 }
+
+void ShenandoahHeapRegion::set_state(RegionState to) {
+  EventShenandoahHeapRegionStateChange evt;
+  if (evt.should_commit()){
+    evt.set_index(region_number());
+    evt.set_start((uintptr_t)bottom());
+    evt.set_used(used());
+    evt.set_from(_state);
+    evt.set_to(to);
+    evt.commit();
+  }
+  _state = to;
+}