--- old/src/hotspot/share/gc/g1/g1IHOPControl.cpp	2020-06-10 10:12:05.537064015 +0200
+++ new/src/hotspot/share/gc/g1/g1IHOPControl.cpp	2020-06-10 10:12:05.445060856 +0200
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2020, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -44,7 +44,7 @@
   _target_occupancy = new_target_occupancy;
 }
 
-void G1IHOPControl::update_allocation_info(double allocation_time_s, size_t allocated_bytes, size_t additional_buffer_size) {
+void G1IHOPControl::update_allocation_info(double allocation_time_s, size_t allocated_bytes) {
   assert(allocation_time_s >= 0.0, "Allocation time must be positive but is %.3f", allocation_time_s);
 
   _last_allocation_time_s = allocation_time_s;
@@ -89,12 +89,23 @@
   _heap_reserve_percent(heap_reserve_percent),
   _heap_waste_percent(heap_waste_percent),
   _predictor(predictor),
-  _marking_times_s(10, 0.95),
-  _allocation_rate_s(10, 0.95),
+  _marking_times_s(10),
+  _allocation_rate_s(10),
   _last_unrestrained_young_size(0)
 {
 }
 
+void G1AdaptiveIHOPControl::update_target_occupancy(size_t new_target_occupancy) {
+  size_t old_target_occupancy = _target_occupancy;
+  G1IHOPControl::update_target_occupancy(new_target_occupancy);
+
+  // When resizing the heap, as an estimate of the new value, scale the
+  // buffer needed linearly.
+  if (old_target_occupancy != 0) {
+    _last_unrestrained_young_size = _last_unrestrained_young_size * (new_target_occupancy / (double)old_target_occupancy);
+  }
+}
+
 size_t G1AdaptiveIHOPControl::actual_target_threshold() const {
   guarantee(_target_occupancy > 0, "Target occupancy still not updated yet.");
   // The actual target threshold takes the heap reserve and the expected waste in
@@ -108,7 +119,7 @@
   double safe_total_heap_percentage = MIN2((double)(_heap_reserve_percent + _heap_waste_percent), 100.0);
 
   return (size_t)MIN2(
-    G1CollectedHeap::heap()->max_capacity() * (100.0 - safe_total_heap_percentage) / 100.0,
+    G1CollectedHeap::heap()->soft_max_capacity() * (100.0 - safe_total_heap_percentage) / 100.0,
     _target_occupancy * (100.0 - _heap_waste_percent) / 100.0
     );
 }
@@ -146,14 +157,15 @@
 }
 
 void G1AdaptiveIHOPControl::update_allocation_info(double allocation_time_s,
-                                                   size_t allocated_bytes,
-                                                   size_t additional_buffer_size) {
-  G1IHOPControl::update_allocation_info(allocation_time_s, allocated_bytes, additional_buffer_size);
+                                                   size_t allocated_bytes) {
+  G1IHOPControl::update_allocation_info(allocation_time_s, allocated_bytes);
 
   double allocation_rate = (double) allocated_bytes / allocation_time_s;
   _allocation_rate_s.add(allocation_rate);
+}
 
-  _last_unrestrained_young_size = additional_buffer_size;
+void G1AdaptiveIHOPControl::update_additional_buffer(size_t additional_buffer_bytes) {
+  _last_unrestrained_young_size = additional_buffer_bytes;
 }
 
 void G1AdaptiveIHOPControl::update_marking_length(double marking_length_s) {