--- old/src/hotspot/share/services/virtualMemoryTracker.hpp	2018-02-15 14:25:51.432101645 +0100
+++ new/src/hotspot/share/services/virtualMemoryTracker.hpp	2018-02-15 14:25:51.224094592 +0100
@@ -210,6 +210,8 @@
 
 
   inline bool overlap_region(address addr, size_t sz) const {
+    assert(sz > 0, "Invalid size");
+    assert(size() > 0, "Invalid size");
     VirtualMemoryRegion rgn(addr, sz);
     return contain_address(addr) ||
            contain_address(addr + sz - 1) ||
@@ -295,18 +297,14 @@
   NativeCallStack  _stack;
   MEMFLAGS         _flag;
 
-  bool             _all_committed;
-
  public:
   ReservedMemoryRegion(address base, size_t size, const NativeCallStack& stack,
     MEMFLAGS flag = mtNone) :
-    VirtualMemoryRegion(base, size), _stack(stack), _flag(flag),
-    _all_committed(false) { }
+    VirtualMemoryRegion(base, size), _stack(stack), _flag(flag) { }
 
 
   ReservedMemoryRegion(address base, size_t size) :
-    VirtualMemoryRegion(base, size), _stack(NativeCallStack::EMPTY_STACK), _flag(mtNone),
-    _all_committed(false) { }
+    VirtualMemoryRegion(base, size), _stack(NativeCallStack::EMPTY_STACK), _flag(mtNone) { }
 
   // Copy constructor
   ReservedMemoryRegion(const ReservedMemoryRegion& rr) :
@@ -347,9 +345,6 @@
   // the new region
   void    move_committed_regions(address addr, ReservedMemoryRegion& rgn);
 
-  inline bool all_committed() const { return _all_committed; }
-  void        set_all_committed(bool b);
-
   CommittedRegionIterator iterate_committed_regions() const {
     return CommittedRegionIterator(_committed_regions.head());
   }
@@ -360,17 +355,14 @@
 
     _stack =         *other.call_stack();
     _flag  =         other.flag();
-    _all_committed = other.all_committed();
-    if (other.all_committed()) {
-      set_all_committed(true);
-    } else {
-      CommittedRegionIterator itr = other.iterate_committed_regions();
-      const CommittedMemoryRegion* rgn = itr.next();
-      while (rgn != NULL) {
-        _committed_regions.add(*rgn);
-        rgn = itr.next();
-      }
+
+    CommittedRegionIterator itr = other.iterate_committed_regions();
+    const CommittedMemoryRegion* rgn = itr.next();
+    while (rgn != NULL) {
+      _committed_regions.add(*rgn);
+      rgn = itr.next();
     }
+
     return *this;
   }
 
@@ -380,6 +372,8 @@
   bool remove_uncommitted_region(LinkedListNode<CommittedMemoryRegion>* node,
     address addr, size_t sz);
 
+  void merge_with(LinkedListNode<CommittedMemoryRegion>* node, address addr, size_t size, const NativeCallStack& stack);
+
   bool add_committed_region(const CommittedMemoryRegion& rgn) {
     assert(rgn.base() != NULL, "Invalid base address");
     assert(size() > 0, "Invalid size");
@@ -396,14 +390,15 @@
 
 // Main class called from MemTracker to track virtual memory allocations, commits and releases.
 class VirtualMemoryTracker : AllStatic {
+  friend class VirtualMemoryTrackerTest;
+
  public:
   static bool initialize(NMT_TrackingLevel level);
 
   // Late phase initialization
   static bool late_initialize(NMT_TrackingLevel level);
 
-  static bool add_reserved_region (address base_addr, size_t size, const NativeCallStack& stack,
-    MEMFLAGS flag = mtNone, bool all_committed = false);
+  static bool add_reserved_region (address base_addr, size_t size, const NativeCallStack& stack, MEMFLAGS flag = mtNone);
 
   static bool add_committed_region      (address base_addr, size_t size, const NativeCallStack& stack);
   static bool remove_uncommitted_region (address base_addr, size_t size);