--- old/src/hotspot/share/gc/g1/g1Policy.cpp	2020-02-19 11:43:18.797786770 +0100
+++ new/src/hotspot/share/gc/g1/g1Policy.cpp	2020-02-19 11:43:18.391774085 +0100
@@ -32,6 +32,7 @@
 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
 #include "gc/g1/g1ConcurrentRefine.hpp"
 #include "gc/g1/g1CollectionSetChooser.hpp"
+#include "gc/g1/g1HeapSizingPolicy.hpp"
 #include "gc/g1/g1HeterogeneousHeapPolicy.hpp"
 #include "gc/g1/g1HotCardCache.hpp"
 #include "gc/g1/g1IHOPControl.hpp"
@@ -76,6 +77,7 @@
   _total_concurrent_refined_cards(0),
   _total_concurrent_refinement_time(),
   _bytes_allocated_in_old_since_last_gc(0),
+  _minimum_desired_bytes_after_last_cm(0),
   _initial_mark_to_mixed(),
   _collection_set(NULL),
   _g1h(NULL),
@@ -1095,6 +1097,21 @@
   }
 }
 
+void G1Policy::determine_desired_bytes_after_concurrent_mark() {
+  size_t cur_used_bytes = _g1h->non_young_capacity_bytes();
+
+  size_t overall_target_capacity = _g1h->heap_sizing_policy()->target_heap_capacity(cur_used_bytes, MinHeapFreeRatio);
+
+  size_t desired_bytes_after_concurrent_mark = _g1h->policy()->desired_bytes_after_concurrent_mark(cur_used_bytes);
+
+  _minimum_desired_bytes_after_last_cm = MIN2(desired_bytes_after_concurrent_mark, overall_target_capacity);
+
+  log_debug(gc, ergo, heap)("Expansion amount after remark used: " SIZE_FORMAT " "
+                            "minimum_desired_capacity " SIZE_FORMAT " desired_bytes_after_concurrent_mark: " SIZE_FORMAT " "
+                            "minimum_desired_bytes_after_concurrent_mark " SIZE_FORMAT,
+                            cur_used_bytes, overall_target_capacity, desired_bytes_after_concurrent_mark, _minimum_desired_bytes_after_last_cm);
+}
+
 void G1Policy::record_concurrent_mark_cleanup_end() {
   G1CollectionSetCandidates* candidates = G1CollectionSetChooser::build(_g1h->workers(), _g1h->num_regions());
   _collection_set->set_candidates(candidates);
@@ -1107,6 +1124,8 @@
   collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending);
   collector_state()->set_mark_or_rebuild_in_progress(false);
 
+  determine_desired_bytes_after_concurrent_mark();
+
   double end_sec = os::elapsedTime();
   double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
   _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
@@ -1199,8 +1218,10 @@
                                        const char* false_action_str) const {
   G1CollectionSetCandidates* candidates = _collection_set->candidates();
 
-  if (candidates->is_empty()) {
-    log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
+  if (candidates == NULL || candidates->is_empty()) {
+    if (false_action_str != NULL) {
+      log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
+    }
     return false;
   }
 
@@ -1209,12 +1230,16 @@
   double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
   double threshold = (double) G1HeapWastePercent;
   if (reclaimable_percent <= threshold) {
-    log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
-                        false_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
+    if (false_action_str != NULL) {
+      log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
+                          false_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
+    }
     return false;
   }
-  log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
-                      true_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
+  if (true_action_str != NULL) {
+    log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
+                        true_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
+  }
   return true;
 }
 
@@ -1411,3 +1436,10 @@
   // the survivor regions from this evacuation pause as 'young'
   // at the start of the next.
 }
+
+size_t G1Policy::desired_bytes_after_concurrent_mark(size_t used_bytes) {
+  size_t minimum_desired_buffer_size = _ihop_control->predict_unrestrained_buffer_size();
+  return minimum_desired_buffer_size != 0 ?
+           minimum_desired_buffer_size :
+           _young_list_max_length * HeapRegion::GrainBytes + _reserve_regions * HeapRegion::GrainBytes + used_bytes;
+}