6634032: CMS: Need CMSInitiatingPermOccupancyFraction for perm, divorcing from CMSInitiatingOccupancyFraction

The option CMSInitiatingPermOccupancyFraction now controls perm triggering threshold. Even though the actual value of the threshold has not yet been changed, so there is no change in policy, we now have the infrastructure in place for dynamically deciding when to collect the perm gen, an issue that will be addressed in the near future.

Reviewed-by: jmasa

hotspot/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.hpp

@@ -535,13 +535,16 @@ class CMSCollector: public CHeapObj {
   // In support of ExplicitGCInvokesConcurrent
   static   bool _full_gc_requested;
   unsigned int  _collection_count_start;
+
   // Should we unload classes this concurrent cycle?
-  // Set in response to a concurrent full gc request.
-  bool _unload_classes;
-  bool _unloaded_classes_last_cycle;
+  bool _should_unload_classes;
+  unsigned int  _concurrent_cycles_since_last_unload;
+  unsigned int concurrent_cycles_since_last_unload() const {
+    return _concurrent_cycles_since_last_unload;
+  }
   // Did we (allow) unload classes in the previous concurrent cycle?
-  bool cms_unloaded_classes_last_cycle() const {
-    return _unloaded_classes_last_cycle || CMSClassUnloadingEnabled;
+  bool unloaded_classes_last_cycle() const {
+    return concurrent_cycles_since_last_unload() == 0;
   }
 
   // Verification support
@@ -651,8 +654,6 @@ class CMSCollector: public CHeapObj {
   // number of full gc's since the last concurrent gc.
   uint   _full_gcs_since_conc_gc;
 
-  // if occupancy exceeds this, start a new gc cycle
-  double _initiatingOccupancy;
   // occupancy used for bootstrapping stats
   double _bootstrap_occupancy;
 
@@ -825,7 +826,6 @@ class CMSCollector: public CHeapObj {
 
   Mutex* bitMapLock()        const { return _markBitMap.lock();    }
   static CollectorState abstract_state() { return _collectorState;  }
-  double initiatingOccupancy() const { return _initiatingOccupancy; }
 
   bool should_abort_preclean() const; // Whether preclean should be aborted.
   size_t get_eden_used() const;
@@ -849,11 +849,10 @@ class CMSCollector: public CHeapObj {
   // In support of ExplicitGCInvokesConcurrent
   static void request_full_gc(unsigned int full_gc_count);
   // Should we unload classes in a particular concurrent cycle?
-  bool cms_should_unload_classes() const {
-    assert(!_unload_classes ||  ExplicitGCInvokesConcurrentAndUnloadsClasses,
-           "Inconsistency; see CR 6541037");
-    return _unload_classes || CMSClassUnloadingEnabled;
+  bool should_unload_classes() const {
+    return _should_unload_classes;
   }
+  bool update_should_unload_classes();
 
   void direct_allocated(HeapWord* start, size_t size);
 
@@ -1022,6 +1021,10 @@ class ConcurrentMarkSweepGeneration: public CardGeneration {
     _incremental_collection_failed = false;
   }
 
+  // accessors
+  void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
+  CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
+
  private:
   // For parallel young-gen GC support.
   CMSParGCThreadState** _par_gc_thread_states;
@@ -1029,10 +1032,6 @@ class ConcurrentMarkSweepGeneration: public CardGeneration {
   // Reason generation was expanded
   CMSExpansionCause::Cause _expansion_cause;
 
-  // accessors
-  void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
-  CMSExpansionCause::Cause expansion_cause() { return _expansion_cause; }
-
   // In support of MinChunkSize being larger than min object size
   const double _dilatation_factor;
 
@@ -1045,6 +1044,10 @@ class ConcurrentMarkSweepGeneration: public CardGeneration {
 
   CollectionTypes _debug_collection_type;
 
+  // Fraction of current occupancy at which to start a CMS collection which
+  // will collect this generation (at least).
+  double _initiating_occupancy;
+
  protected:
   // Grow generation by specified size (returns false if unable to grow)
   bool grow_by(size_t bytes);
@@ -1060,6 +1063,10 @@ class ConcurrentMarkSweepGeneration: public CardGeneration {
   // space.
   size_t max_available() const;
 
+  // getter and initializer for _initiating_occupancy field.
+  double initiating_occupancy() const { return _initiating_occupancy; }
+  void   init_initiating_occupancy(intx io, intx tr);
+
  public:
   ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
                                 int level, CardTableRS* ct,
@@ -1103,7 +1110,7 @@ class ConcurrentMarkSweepGeneration: public CardGeneration {
   size_t capacity() const;
   size_t used() const;
   size_t free() const;
-  double occupancy()      { return ((double)used())/((double)capacity()); }
+  double occupancy() const { return ((double)used())/((double)capacity()); }
   size_t contiguous_available() const;
   size_t unsafe_max_alloc_nogc() const;
 
@@ -1158,8 +1165,8 @@ class ConcurrentMarkSweepGeneration: public CardGeneration {
     bool younger_handles_promotion_failure) const;
 
   bool should_collect(bool full, size_t size, bool tlab);
-    // XXXPERM
-  bool shouldConcurrentCollect(double initiatingOccupancy); // XXXPERM
+  virtual bool should_concurrent_collect() const;
+  virtual bool is_too_full() const;
   void collect(bool   full,
                bool   clear_all_soft_refs,
                size_t size,