1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   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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  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).
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  24 
  25 #ifndef SHARE_GC_SERIAL_DEFNEWGENERATION_HPP
  26 #define SHARE_GC_SERIAL_DEFNEWGENERATION_HPP
  27 
  28 #include "gc/serial/cSpaceCounters.hpp"
  29 #include "gc/shared/ageTable.hpp"
  30 #include "gc/shared/copyFailedInfo.hpp"
  31 #include "gc/shared/generation.hpp"
  32 #include "gc/shared/generationCounters.hpp"
  33 #include "gc/shared/preservedMarks.hpp"
  34 #include "utilities/align.hpp"
  35 #include "utilities/stack.hpp"
  36 
  37 class ContiguousSpace;
  38 class ScanClosure;
  39 class STWGCTimer;
  40 class CSpaceCounters;
  41 class ScanWeakRefClosure;
  42 class SerialHeap;
  43 
  44 // DefNewGeneration is a young generation containing eden, from- and
  45 // to-space.
  46 
  47 class DefNewGeneration: public Generation {
  48   friend class VMStructs;
  49 
  50 protected:
  51   Generation* _old_gen;
  52   uint        _tenuring_threshold;   // Tenuring threshold for next collection.
  53   AgeTable    _age_table;
  54   // Size of object to pretenure in words; command line provides bytes
  55   size_t      _pretenure_size_threshold_words;
  56 
  57   AgeTable*   age_table() { return &_age_table; }
  58 
  59   // Initialize state to optimistically assume no promotion failure will
  60   // happen.
  61   void   init_assuming_no_promotion_failure();
  62   // True iff a promotion has failed in the current collection.
  63   bool   _promotion_failed;
  64   bool   promotion_failed() { return _promotion_failed; }
  65   PromotionFailedInfo _promotion_failed_info;
  66 
  67   // Handling promotion failure.  A young generation collection
  68   // can fail if a live object cannot be copied out of its
  69   // location in eden or from-space during the collection.  If
  70   // a collection fails, the young generation is left in a
  71   // consistent state such that it can be collected by a
  72   // full collection.
  73   //   Before the collection
  74   //     Objects are in eden or from-space
  75   //     All roots into the young generation point into eden or from-space.
  76   //
  77   //   After a failed collection
  78   //     Objects may be in eden, from-space, or to-space
  79   //     An object A in eden or from-space may have a copy B
  80   //       in to-space.  If B exists, all roots that once pointed
  81   //       to A must now point to B.
  82   //     All objects in the young generation are unmarked.
  83   //     Eden, from-space, and to-space will all be collected by
  84   //       the full collection.
  85   void handle_promotion_failure(oop);
  86 
  87   // In the absence of promotion failure, we wouldn't look at "from-space"
  88   // objects after a young-gen collection.  When promotion fails, however,
  89   // the subsequent full collection will look at from-space objects:
  90   // therefore we must remove their forwarding pointers.
  91   void remove_forwarding_pointers();
  92 
  93   virtual void restore_preserved_marks();
  94 
  95   // Preserved marks
  96   PreservedMarksSet _preserved_marks_set;
  97 
  98   // Promotion failure handling
  99   OopIterateClosure *_promo_failure_scan_stack_closure;
 100   void set_promo_failure_scan_stack_closure(OopIterateClosure *scan_stack_closure) {
 101     _promo_failure_scan_stack_closure = scan_stack_closure;
 102   }
 103 
 104   Stack<oop, mtGC> _promo_failure_scan_stack;
 105   void drain_promo_failure_scan_stack(void);
 106   bool _promo_failure_drain_in_progress;
 107 
 108   // Performance Counters
 109   GenerationCounters*  _gen_counters;
 110   CSpaceCounters*      _eden_counters;
 111   CSpaceCounters*      _from_counters;
 112   CSpaceCounters*      _to_counters;
 113 
 114   // sizing information
 115   size_t               _max_eden_size;
 116   size_t               _max_survivor_size;
 117 
 118   // Allocation support
 119   bool _should_allocate_from_space;
 120   bool should_allocate_from_space() const {
 121     return _should_allocate_from_space;
 122   }
 123   void clear_should_allocate_from_space() {
 124     _should_allocate_from_space = false;
 125   }
 126   void set_should_allocate_from_space() {
 127     _should_allocate_from_space = true;
 128   }
 129 
 130   // Tenuring
 131   void adjust_desired_tenuring_threshold();
 132 
 133   // Spaces
 134   ContiguousSpace* _eden_space;
 135   ContiguousSpace* _from_space;
 136   ContiguousSpace* _to_space;
 137 
 138   STWGCTimer* _gc_timer;
 139 
 140   enum SomeProtectedConstants {
 141     // Generations are GenGrain-aligned and have size that are multiples of
 142     // GenGrain.
 143     MinFreeScratchWords = 100
 144   };
 145 
 146   // Return the size of a survivor space if this generation were of size
 147   // gen_size.
 148   size_t compute_survivor_size(size_t gen_size, size_t alignment) const {
 149     size_t n = gen_size / (SurvivorRatio + 2);
 150     return n > alignment ? align_down(n, alignment) : alignment;
 151   }
 152 
 153  public:  // was "protected" but caused compile error on win32
 154   class IsAliveClosure: public BoolObjectClosure {
 155     Generation* _young_gen;
 156   public:
 157     IsAliveClosure(Generation* young_gen);
 158     bool do_object_b(oop p);
 159   };
 160 
 161   class KeepAliveClosure: public OopClosure {
 162   protected:
 163     ScanWeakRefClosure* _cl;
 164     CardTableRS* _rs;
 165     template <class T> void do_oop_work(T* p);
 166   public:
 167     KeepAliveClosure(ScanWeakRefClosure* cl);
 168     virtual void do_oop(oop* p);
 169     virtual void do_oop(narrowOop* p);
 170   };
 171 
 172   class FastKeepAliveClosure: public KeepAliveClosure {
 173   protected:
 174     HeapWord* _boundary;
 175     template <class T> void do_oop_work(T* p);
 176   public:
 177     FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl);
 178     virtual void do_oop(oop* p);
 179     virtual void do_oop(narrowOop* p);
 180   };
 181 
 182   class FastEvacuateFollowersClosure: public VoidClosure {
 183     SerialHeap* _heap;
 184     FastScanClosure* _scan_cur_or_nonheap;
 185     FastScanClosure* _scan_older;
 186   public:
 187     FastEvacuateFollowersClosure(SerialHeap* heap,
 188                                  FastScanClosure* cur,
 189                                  FastScanClosure* older);
 190     void do_void();
 191   };
 192 
 193  public:
 194   DefNewGeneration(ReservedSpace rs, size_t initial_byte_size,
 195                    const char* policy="Serial young collection pauses");
 196 
 197   virtual void ref_processor_init();
 198 
 199   virtual Generation::Name kind() { return Generation::DefNew; }
 200 
 201   // Accessing spaces
 202   ContiguousSpace* eden() const           { return _eden_space; }
 203   ContiguousSpace* from() const           { return _from_space; }
 204   ContiguousSpace* to()   const           { return _to_space;   }
 205 
 206   virtual CompactibleSpace* first_compaction_space() const;
 207 
 208   // Space enquiries
 209   size_t capacity() const;
 210   size_t used() const;
 211   size_t free() const;
 212   size_t max_capacity() const;
 213   size_t capacity_before_gc() const;
 214   size_t unsafe_max_alloc_nogc() const;
 215   size_t contiguous_available() const;
 216 
 217   size_t max_eden_size() const              { return _max_eden_size; }
 218   size_t max_survivor_size() const          { return _max_survivor_size; }
 219 
 220   bool supports_inline_contig_alloc() const { return true; }
 221   HeapWord* volatile* top_addr() const;
 222   HeapWord** end_addr() const;
 223 
 224   // Thread-local allocation buffers
 225   bool supports_tlab_allocation() const { return true; }
 226   size_t tlab_capacity() const;
 227   size_t tlab_used() const;
 228   size_t unsafe_max_tlab_alloc() const;
 229 
 230   // Grow the generation by the specified number of bytes.
 231   // The size of bytes is assumed to be properly aligned.
 232   // Return true if the expansion was successful.
 233   bool expand(size_t bytes);
 234 
 235   // DefNewGeneration cannot currently expand except at
 236   // a GC.
 237   virtual bool is_maximal_no_gc() const { return true; }
 238 
 239   // Iteration
 240   void object_iterate(ObjectClosure* blk);
 241 
 242   void younger_refs_iterate(OopsInGenClosure* cl, uint n_threads);
 243 
 244   void space_iterate(SpaceClosure* blk, bool usedOnly = false);
 245 
 246   // Allocation support
 247   virtual bool should_allocate(size_t word_size, bool is_tlab) {
 248     assert(UseTLAB || !is_tlab, "Should not allocate tlab");
 249 
 250     size_t overflow_limit    = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);
 251 
 252     const bool non_zero      = word_size > 0;
 253     const bool overflows     = word_size >= overflow_limit;
 254     const bool check_too_big = _pretenure_size_threshold_words > 0;
 255     const bool not_too_big   = word_size < _pretenure_size_threshold_words;
 256     const bool size_ok       = is_tlab || !check_too_big || not_too_big;
 257 
 258     bool result = !overflows &&
 259                   non_zero   &&
 260                   size_ok;
 261 
 262     return result;
 263   }
 264 
 265   HeapWord* allocate(size_t word_size, bool is_tlab);
 266   HeapWord* allocate_from_space(size_t word_size);
 267 
 268   HeapWord* par_allocate(size_t word_size, bool is_tlab);
 269 
 270   virtual void gc_epilogue(bool full);
 271 
 272   // Save the tops for eden, from, and to
 273   virtual void record_spaces_top();
 274 
 275   // Accessing marks
 276   void save_marks();
 277   void reset_saved_marks();
 278   bool no_allocs_since_save_marks();
 279 
 280   // Need to declare the full complement of closures, whether we'll
 281   // override them or not, or get message from the compiler:
 282   //   oop_since_save_marks_iterate_nv hides virtual function...
 283   template <typename OopClosureType>
 284   void oop_since_save_marks_iterate(OopClosureType* cl);
 285 
 286   // For non-youngest collection, the DefNewGeneration can contribute
 287   // "to-space".
 288   virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor,
 289                           size_t max_alloc_words);
 290 
 291   // Reset for contribution of "to-space".
 292   virtual void reset_scratch();
 293 
 294   // GC support
 295   virtual void compute_new_size();
 296 
 297   // Returns true if the collection is likely to be safely
 298   // completed. Even if this method returns true, a collection
 299   // may not be guaranteed to succeed, and the system should be
 300   // able to safely unwind and recover from that failure, albeit
 301   // at some additional cost. Override superclass's implementation.
 302   virtual bool collection_attempt_is_safe();
 303 
 304   virtual void collect(bool   full,
 305                        bool   clear_all_soft_refs,
 306                        size_t size,
 307                        bool   is_tlab);
 308   HeapWord* expand_and_allocate(size_t size,
 309                                 bool is_tlab,
 310                                 bool parallel = false);
 311 
 312   oop copy_to_survivor_space(oop old);
 313   uint tenuring_threshold() { return _tenuring_threshold; }
 314 
 315   // Performance Counter support
 316   void update_counters();
 317 
 318   // Printing
 319   virtual const char* name() const;
 320   virtual const char* short_name() const { return "DefNew"; }
 321 
 322   void print_on(outputStream* st) const;
 323 
 324   void verify();
 325 
 326   bool promo_failure_scan_is_complete() const {
 327     return _promo_failure_scan_stack.is_empty();
 328   }
 329 
 330  protected:
 331   // If clear_space is true, clear the survivor spaces.  Eden is
 332   // cleared if the minimum size of eden is 0.  If mangle_space
 333   // is true, also mangle the space in debug mode.
 334   void compute_space_boundaries(uintx minimum_eden_size,
 335                                 bool clear_space,
 336                                 bool mangle_space);
 337 
 338   // Return adjusted new size for NewSizeThreadIncrease.
 339   // If any overflow happens, revert to previous new size.
 340   size_t adjust_for_thread_increase(size_t new_size_candidate,
 341                                     size_t new_size_before,
 342                                     size_t alignment) const;
 343 
 344 
 345   // Scavenge support
 346   void swap_spaces();
 347 };
 348 
 349 #endif // SHARE_GC_SERIAL_DEFNEWGENERATION_HPP