--- old/src/hotspot/share/gc/g1/g1CollectedHeap.hpp	2020-01-03 17:56:50.193807800 +0800
+++ new/src/hotspot/share/gc/g1/g1CollectedHeap.hpp	2020-01-03 17:56:50.195807871 +0800
@@ -30,6 +30,7 @@
 #include "gc/g1/g1CardTable.hpp"
 #include "gc/g1/g1CollectionSet.hpp"
 #include "gc/g1/g1CollectorState.hpp"
+#include "gc/g1/g1ConcurrentHeapResize.hpp"
 #include "gc/g1/g1ConcurrentMark.hpp"
 #include "gc/g1/g1EdenRegions.hpp"
 #include "gc/g1/g1EvacFailure.hpp"
@@ -80,6 +81,8 @@
 class G1HotCardCache;
 class G1RemSet;
 class G1YoungRemSetSamplingThread;
+class G1ConcurrentHeapResize;
+class G1ConcurrentHeapResizeThread;
 class G1ConcurrentMark;
 class G1ConcurrentMarkThread;
 class G1ConcurrentRefine;
@@ -235,6 +238,10 @@
   // start of each GC.
   bool _expand_heap_after_alloc_failure;
 
+  // The previous value of SoftMaxHeapSize to indicate if a new value is assigned
+  // The default value is MaxHeapSize
+  size_t _prev_soft_max_heap_size;
+
   // Helper for monitoring and management support.
   G1MonitoringSupport* _g1mm;
 
@@ -511,11 +518,14 @@
   void abort_concurrent_cycle();
   void verify_before_full_collection(bool explicit_gc);
   void prepare_heap_for_full_collection();
-  void prepare_heap_for_mutators();
+  void prepare_heap_for_mutators(bool explicit_gc);
   void abort_refinement();
   void verify_after_full_collection();
   void print_heap_after_full_collection(G1HeapTransition* heap_transition);
 
+  // Check if SoftMaxHeapSize has changed in runtime
+  bool check_soft_max_heap_size_changed();
+
   // Helper method for satisfy_failed_allocation()
   HeapWord* satisfy_failed_allocation_helper(size_t word_size,
                                              bool do_gc,
@@ -565,7 +575,7 @@
     return _g1mm;
   }
 
-  void resize_heap_if_necessary();
+  void resize_heap_if_necessary(bool limit_within_soft_max_heap_size);
 
   G1NUMA* numa() const { return _numa; }
 
@@ -781,7 +791,10 @@
                                     G1RedirtyCardsQueueSet* rdcqs,
                                     G1ParScanThreadStateSet* pss);
 
+  void adjust_heap_after_young_collection();
   void expand_heap_after_young_collection();
+  void shrink_heap_after_young_collection();
+
   // Update object copying statistics.
   void record_obj_copy_mem_stats();
 
@@ -806,6 +819,10 @@
   // The concurrent refiner.
   G1ConcurrentRefine* _cr;
 
+  // The concurrent heap resizer (and the thread it runs in.)
+  G1ConcurrentHeapResize* _concurrent_heap_resize;
+  G1ConcurrentHeapResizeThread* _concurrent_heap_resize_thread;
+
   // The parallel task queues
   RefToScanQueueSet *_task_queues;
 
@@ -1078,7 +1095,7 @@
 
   inline void archive_set_add(HeapRegion* hr);
 
-  size_t non_young_capacity_bytes() {
+  size_t non_young_capacity_bytes() const {
     return (old_regions_count() + _archive_set.length() + humongous_regions_count()) * HeapRegion::GrainBytes;
   }
 
@@ -1358,6 +1375,9 @@
 
   G1ConcurrentRefine* concurrent_refine() const { return _cr; }
 
+  // Concurrent heap resizing
+  G1ConcurrentHeapResize* concurrent_heap_resize() const { return _concurrent_heap_resize; }
+
   // Optimized nmethod scanning support routines
 
   // Register the given nmethod with the G1 heap.