--- old/src/hotspot/share/gc/g1/g1Policy.cpp	2020-02-11 11:34:49.216234312 +0100
+++ new/src/hotspot/share/gc/g1/g1Policy.cpp	2020-02-11 11:34:48.810221830 +0100
@@ -179,18 +179,38 @@
   }
 };
 
-void G1Policy::record_new_heap_size(uint new_number_of_regions) {
-  // re-calculate the necessary reserve
-  double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
-  // We use ceiling so that if reserve_regions_d is > 0.0 (but
-  // smaller than 1.0) we'll get 1.
-  _reserve_regions = (uint) ceil(reserve_regions_d);
-
+void G1Policy::record_new_target_heap_size(uint new_number_of_regions, uint reserve_regions) {
+  _reserve_regions = reserve_regions;
   _young_gen_sizer->heap_size_changed(new_number_of_regions);
-
   _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
 }
 
+void G1Policy::update_heap_target_size(uint num_regions, uint soft_goal_num_regions) {
+  uint desired_number_of_regions = MIN2(num_regions, soft_goal_num_regions);
+  
+  uint regular_reserve_regions = (uint)ceil((double)num_regions * G1ReservePercent / 100);
+  uint reserve_regions = regular_reserve_regions;
+  uint soft_reserve_regions = 0;
+
+  if (soft_goal_num_regions < num_regions) {
+    soft_reserve_regions = num_regions - soft_goal_num_regions + 
+            (uint)ceil((double)soft_goal_num_regions * G1ReservePercent / 100);
+    reserve_regions = soft_reserve_regions;
+  }
+
+  // FIXME: this method is called very early during startup during initial heap expansion, so
+  // the _g1h member has not been set yet.
+  G1CollectedHeap* g1h = G1CollectedHeap::heap();
+  uint MBPerRegion = HeapRegion::GrainBytes / (1024 * 1024);
+  log_error(gc)("heap target update: soft-goal %u committed %u goal %u hard-reserve %u soft-reserve %u reserve %u free %u used %u",
+                soft_goal_num_regions * MBPerRegion, num_regions * MBPerRegion,
+                desired_number_of_regions * MBPerRegion,
+                regular_reserve_regions * MBPerRegion, soft_reserve_regions * MBPerRegion, reserve_regions * MBPerRegion,
+                g1h->num_free_regions() * MBPerRegion, g1h->num_used_regions() * MBPerRegion);
+
+  record_new_target_heap_size(desired_number_of_regions, reserve_regions);
+}
+
 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const {
   uint desired_min_length = 0;
   if (use_adaptive_young_list_length()) {