psScavenge.hpp

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#ifndef SHARE_GC_PARALLEL_PSSCAVENGE_HPP
#define SHARE_GC_PARALLEL_PSSCAVENGE_HPP

#include "gc/parallel/psCardTable.hpp"
#include "gc/parallel/psVirtualspace.hpp"
#include "gc/shared/collectorCounters.hpp"
#include "gc/shared/gcTrace.hpp"
#include "memory/allocation.hpp"
#include "oops/oop.hpp"
#include "utilities/stack.hpp"

class OopStack;
class ReferenceProcessor;
class ParallelScavengeHeap;
class ParallelScavengeTracer;
class PSIsAliveClosure;
class PSRefProcTaskExecutor;
class STWGCTimer;

class PSScavenge: AllStatic {
  friend class PSIsAliveClosure;
  friend class PSKeepAliveClosure;
  friend class PSPromotionManager;

 enum ScavengeSkippedCause {
   not_skipped = 0,
   to_space_not_empty,
   promoted_too_large,
   full_follows_scavenge
 };

  // Saved value of to_space->top(), used to prevent objects in to_space from
  // being rescanned.
  static HeapWord* _to_space_top_before_gc;

  // Number of consecutive attempts to scavenge that were skipped
  static int                _consecutive_skipped_scavenges;


 protected:
  // Flags/counters
  static SpanSubjectToDiscoveryClosure _span_based_discoverer;
  static ReferenceProcessor*           _ref_processor;        // Reference processor for scavenging.
  static PSIsAliveClosure              _is_alive_closure;     // Closure used for reference processing
  static PSCardTable*                  _card_table;           // We cache the card table for fast access.
  static bool                          _survivor_overflow;    // Overflow this collection
  static uint                          _tenuring_threshold;   // tenuring threshold for next scavenge
  static elapsedTimer                  _accumulated_time;     // total time spent on scavenge
  static STWGCTimer                    _gc_timer;             // GC time book keeper
  static ParallelScavengeTracer        _gc_tracer;          // GC tracing
  // The lowest address possible for the young_gen.
  // This is used to decide if an oop should be scavenged,
  // cards should be marked, etc.
  static HeapWord*            _young_generation_boundary;
  // Used to optimize compressed oops young gen boundary checking.
  static uintptr_t            _young_generation_boundary_compressed;
  static CollectorCounters*   _counters;             // collector performance counters

  static void clean_up_failed_promotion();

  static bool should_attempt_scavenge();

  static HeapWord* to_space_top_before_gc() { return _to_space_top_before_gc; }
  static inline void save_to_space_top_before_gc();

  // Private accessors
  static PSCardTable* const card_table()           { assert(_card_table != NULL, "Sanity"); return _card_table; }
  static const ParallelScavengeTracer* gc_tracer() { return &_gc_tracer; }

 public:
  // Accessors
  static uint             tenuring_threshold()  { return _tenuring_threshold; }
  static elapsedTimer*    accumulated_time()    { return &_accumulated_time; }
  static int              consecutive_skipped_scavenges()
    { return _consecutive_skipped_scavenges; }

  // Performance Counters
  static CollectorCounters* counters()           { return _counters; }

  static void set_subject_to_discovery_span(MemRegion mr) {
    _span_based_discoverer.set_span(mr);
  }
  // Used by scavenge_contents
  static ReferenceProcessor* const reference_processor() {
    assert(_ref_processor != NULL, "Sanity");
    return _ref_processor;
  }
  // The promotion managers tell us if they encountered overflow
  static void set_survivor_overflow(bool state) {
    _survivor_overflow = state;
  }
  // Adaptive size policy support.
  static void set_young_generation_boundary(HeapWord* v);

  // Called by parallelScavengeHeap to init the tenuring threshold
  static void initialize();

  // Scavenge entry point.  This may invoke a full gc; return true if so.
  static bool invoke();
  // Return true if a collection was done; false otherwise.
  static bool invoke_no_policy();

  template <class T> static inline bool should_scavenge(T* p);

  // These call should_scavenge() above and, if it returns true, also check that
  // the object was not newly copied into to_space.  The version with the bool
  // argument is a convenience wrapper that fetches the to_space pointer from
  // the heap and calls the other version (if the arg is true).
  template <class T> static inline bool should_scavenge(T* p, MutableSpace* to_space);
  template <class T> static inline bool should_scavenge(T* p, bool check_to_space);

  static void copy_and_push_safe_barrier_from_klass(PSPromotionManager* pm, oop* p);

  // Is an object in the young generation
  // This assumes that the 'o' is in the heap,
  // so it only checks one side of the complete predicate.

  inline static bool is_obj_in_young(oop o) {
    return cast_from_oop<HeapWord*>(o) >= _young_generation_boundary;
  }

  inline static bool is_obj_in_young(narrowOop o) {
    return (uintptr_t)o >= _young_generation_boundary_compressed;
  }

  inline static bool is_obj_in_young(HeapWord* o) {
    return o >= _young_generation_boundary;
  }
};

#endif // SHARE_GC_PARALLEL_PSSCAVENGE_HPP