--- old/src/hotspot/share/gc/cms/compactibleFreeListSpace.cpp	Fri Jun 21 17:34:04 2019
+++ new/src/hotspot/share/gc/cms/compactibleFreeListSpace.cpp	Fri Jun 21 17:34:03 2019
@@ -372,6 +372,8 @@
     )
   }
   _dictionary->set_par_lock(&_parDictionaryAllocLock);
+
+  _used_stable = 0;
 }
 
 // Like CompactibleSpace forward() but always calls cross_threshold() to
@@ -577,6 +579,14 @@
   return capacity() - free();
 }
 
+size_t CompactibleFreeListSpace::used_stable() const {
+  return _used_stable;
+}
+
+void CompactibleFreeListSpace::recalculate_used_stable() {
+  _used_stable = used();
+}
+
 size_t CompactibleFreeListSpace::free() const {
   // "MT-safe, but not MT-precise"(TM), if you will: i.e.
   // if you do this while the structures are in flux you
@@ -1374,6 +1384,9 @@
     debug_only(fc->mangleAllocated(size));
   }
 
+  // After allocation, recalculate used space and update used_stable
+  recalculate_used_stable();
+
   return res;
 }