diff -r c97db0855565 -r 758c07667682 src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.cpp
--- a/src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.cpp	Tue Feb 04 17:38:01 2020 +0800
+++ b/src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.cpp	Tue Feb 04 18:13:14 2020 +0800
@@ -161,6 +161,8 @@
     }
     _dictionary->set_par_lock(&_parDictionaryAllocLock);
   }
+
+  _used_stable = 0;
 }
 
 // Like CompactibleSpace forward() but always calls cross_threshold() to
@@ -377,6 +379,14 @@
   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
@@ -1218,6 +1228,13 @@
     debug_only(fc->mangleAllocated(size));
   }
 
+  // During GC we do not need to recalculate the stable used value for
+  // every allocation in old gen. It is done once at the end of GC instead
+  // for performance reasons.
+  if (!Universe::heap()->is_gc_active()) {
+    recalculate_used_stable();
+  }
+
   return res;
 }