1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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  24 
  25 #ifndef SHARE_GC_PARALLEL_PSSCAVENGE_HPP
  26 #define SHARE_GC_PARALLEL_PSSCAVENGE_HPP
  27 
  28 #include "gc/parallel/psCardTable.hpp"
  29 #include "gc/parallel/psVirtualspace.hpp"
  30 #include "gc/shared/collectorCounters.hpp"
  31 #include "gc/shared/gcTrace.hpp"
  32 #include "memory/allocation.hpp"
  33 #include "oops/oop.hpp"
  34 #include "utilities/stack.hpp"
  35 
  36 class OopStack;
  37 class ReferenceProcessor;
  38 class ParallelScavengeHeap;
  39 class ParallelScavengeTracer;
  40 class PSIsAliveClosure;
  41 class PSRefProcTaskExecutor;
  42 class STWGCTimer;
  43 
  44 class PSScavenge: AllStatic {
  45   friend class PSIsAliveClosure;
  46   friend class PSKeepAliveClosure;
  47   friend class PSPromotionManager;
  48 
  49  enum ScavengeSkippedCause {
  50    not_skipped = 0,
  51    to_space_not_empty,
  52    promoted_too_large,
  53    full_follows_scavenge
  54  };
  55 
  56   // Saved value of to_space->top(), used to prevent objects in to_space from
  57   // being rescanned.
  58   static HeapWord* _to_space_top_before_gc;
  59 
  60   // Number of consecutive attempts to scavenge that were skipped
  61   static int                _consecutive_skipped_scavenges;
  62 
  63 
  64  protected:
  65   // Flags/counters
  66   static SpanSubjectToDiscoveryClosure _span_based_discoverer;
  67   static ReferenceProcessor*           _ref_processor;        // Reference processor for scavenging.
  68   static PSIsAliveClosure              _is_alive_closure;     // Closure used for reference processing
  69   static PSCardTable*                  _card_table;           // We cache the card table for fast access.
  70   static bool                          _survivor_overflow;    // Overflow this collection
  71   static uint                          _tenuring_threshold;   // tenuring threshold for next scavenge
  72   static elapsedTimer                  _accumulated_time;     // total time spent on scavenge
  73   static STWGCTimer                    _gc_timer;             // GC time book keeper
  74   static ParallelScavengeTracer        _gc_tracer;          // GC tracing
  75   // The lowest address possible for the young_gen.
  76   // This is used to decide if an oop should be scavenged,
  77   // cards should be marked, etc.
  78   static HeapWord*            _young_generation_boundary;
  79   // Used to optimize compressed oops young gen boundary checking.
  80   static uintptr_t            _young_generation_boundary_compressed;
  81   static CollectorCounters*   _counters;             // collector performance counters
  82 
  83   static void clean_up_failed_promotion();
  84 
  85   static bool should_attempt_scavenge();
  86 
  87   static HeapWord* to_space_top_before_gc() { return _to_space_top_before_gc; }
  88   static inline void save_to_space_top_before_gc();
  89 
  90   // Private accessors
  91   static PSCardTable* const card_table()           { assert(_card_table != NULL, "Sanity"); return _card_table; }
  92   static const ParallelScavengeTracer* gc_tracer() { return &_gc_tracer; }
  93 
  94  public:
  95   // Accessors
  96   static uint             tenuring_threshold()  { return _tenuring_threshold; }
  97   static elapsedTimer*    accumulated_time()    { return &_accumulated_time; }
  98   static int              consecutive_skipped_scavenges()
  99     { return _consecutive_skipped_scavenges; }
 100 
 101   // Performance Counters
 102   static CollectorCounters* counters()           { return _counters; }
 103 
 104   static void set_subject_to_discovery_span(MemRegion mr) {
 105     _span_based_discoverer.set_span(mr);
 106   }
 107   // Used by scavenge_contents && psMarkSweep
 108   static ReferenceProcessor* const reference_processor() {
 109     assert(_ref_processor != NULL, "Sanity");
 110     return _ref_processor;
 111   }
 112   // The promotion managers tell us if they encountered overflow
 113   static void set_survivor_overflow(bool state) {
 114     _survivor_overflow = state;
 115   }
 116   // Adaptive size policy support.  When the young generation/old generation
 117   // boundary moves, _young_generation_boundary must be reset
 118   static void set_young_generation_boundary(HeapWord* v);
 119 
 120   // Called by parallelScavengeHeap to init the tenuring threshold
 121   static void initialize();
 122 
 123   // Scavenge entry point.  This may invoke a full gc; return true if so.
 124   static bool invoke();
 125   // Return true if a collection was done; false otherwise.
 126   static bool invoke_no_policy();
 127 
 128   template <class T> static inline bool should_scavenge(T* p);
 129 
 130   // These call should_scavenge() above and, if it returns true, also check that
 131   // the object was not newly copied into to_space.  The version with the bool
 132   // argument is a convenience wrapper that fetches the to_space pointer from
 133   // the heap and calls the other version (if the arg is true).
 134   template <class T> static inline bool should_scavenge(T* p, MutableSpace* to_space);
 135   template <class T> static inline bool should_scavenge(T* p, bool check_to_space);
 136 
 137   static void copy_and_push_safe_barrier_from_klass(PSPromotionManager* pm, oop* p);
 138 
 139   // Is an object in the young generation
 140   // This assumes that the 'o' is in the heap,
 141   // so it only checks one side of the complete predicate.
 142 
 143   inline static bool is_obj_in_young(oop o) {
 144     return (HeapWord*)o >= _young_generation_boundary;
 145   }
 146 
 147   inline static bool is_obj_in_young(narrowOop o) {
 148     return (uintptr_t)o >= _young_generation_boundary_compressed;
 149   }
 150 
 151   inline static bool is_obj_in_young(HeapWord* o) {
 152     return o >= _young_generation_boundary;
 153   }
 154 };
 155 
 156 #endif // SHARE_GC_PARALLEL_PSSCAVENGE_HPP