src/hotspot/share/gc/cms/compactibleFreeListSpace.hpp

*** 190,199 ****
--- 190,202 ----
    HeapWord*  _nearLargestChunk;
  
    // Used to keep track of limit of sweep for the space
    HeapWord* _sweep_limit;
  
+   // Stable value of used().
+   size_t _used_stable;
+ 
    // Used to make the young collector update the mod union table
    MemRegionClosure* _preconsumptionDirtyCardClosure;
  
    // Support for compacting cms
    HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
*** 410,419 ****
--- 413,433 ----
    // try to bump down the address and the allocator will try to bump it up.
    // For now, however, we'll just use the default used_region()
    // which overestimates the region by returning the entire
    // committed region (this is safe, but inefficient).
  
+   // Returns monotonically increasing stable used space bytes for CMS.
+   // This is required for jhat and other memory monitoring tools
+   // that might otherwise see inconsistent used space values during a garbage 
+   // collection, promotion or allocation into compactibleFreeListSpace.
+   // The value returned by this function might be smaller than the
+   // actual value.
+   size_t used_stable() const;
+   // Recalculate and cache the current stable used() value. Only to be called
+   // in places where we can be sure that the result is stable.
+   void recalculate_used_stable();
+ 
    // Returns a subregion of the space containing all the objects in
    // the space.
    MemRegion used_region() const {
      return MemRegion(bottom(),
                       BlockOffsetArrayUseUnallocatedBlock ?