--- a/src/hotspot/share/gc/g1/g1Policy.cpp	Mon Mar 25 08:37:32 2019 -0400
+++ b/src/hotspot/share/gc/g1/g1Policy.cpp	Mon Mar 25 14:11:09 2019 +0100
@@ -1188,9 +1188,11 @@
   return (uint) result;
 }
 
-void G1Policy::finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
+uint G1Policy::finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
   double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms, survivor);
   _collection_set->finalize_old_part(time_remaining_ms);
+
+  return _collection_set->region_length();
 }
 
 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {