1 /*
   2  * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   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.
   8  *
   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  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_MEMORY_DEFNEWGENERATION_HPP
  26 #define SHARE_VM_MEMORY_DEFNEWGENERATION_HPP
  27 
  28 #include "gc_implementation/shared/ageTable.hpp"
  29 #include "gc_implementation/shared/cSpaceCounters.hpp"
  30 #include "gc_implementation/shared/generationCounters.hpp"
  31 #include "gc_implementation/shared/copyFailedInfo.hpp"
  32 #include "memory/generation.inline.hpp"
  33 #include "utilities/stack.hpp"
  34 
  35 class EdenSpace;
  36 class ContiguousSpace;
  37 class ScanClosure;
  38 class STWGCTimer;
  39 
  40 // DefNewGeneration is a young generation containing eden, from- and
  41 // to-space.
  42 
  43 class DefNewGeneration: public Generation {
  44   friend class VMStructs;
  45 
  46 protected:
  47   Generation* _next_gen;
  48   uint        _tenuring_threshold;   // Tenuring threshold for next collection.
  49   ageTable    _age_table;
  50   // Size of object to pretenure in words; command line provides bytes
  51   size_t      _pretenure_size_threshold_words;
  52 
  53   ageTable*   age_table() { return &_age_table; }
  54 
  55   // Initialize state to optimistically assume no promotion failure will
  56   // happen.
  57   void   init_assuming_no_promotion_failure();
  58   // True iff a promotion has failed in the current collection.
  59   bool   _promotion_failed;
  60   bool   promotion_failed() { return _promotion_failed; }
  61   PromotionFailedInfo _promotion_failed_info;
  62 
  63   // Handling promotion failure.  A young generation collection
  64   // can fail if a live object cannot be copied out of its
  65   // location in eden or from-space during the collection.  If
  66   // a collection fails, the young generation is left in a
  67   // consistent state such that it can be collected by a
  68   // full collection.
  69   //   Before the collection
  70   //     Objects are in eden or from-space
  71   //     All roots into the young generation point into eden or from-space.
  72   //
  73   //   After a failed collection
  74   //     Objects may be in eden, from-space, or to-space
  75   //     An object A in eden or from-space may have a copy B
  76   //       in to-space.  If B exists, all roots that once pointed
  77   //       to A must now point to B.
  78   //     All objects in the young generation are unmarked.
  79   //     Eden, from-space, and to-space will all be collected by
  80   //       the full collection.
  81   void handle_promotion_failure(oop);
  82 
  83   // In the absence of promotion failure, we wouldn't look at "from-space"
  84   // objects after a young-gen collection.  When promotion fails, however,
  85   // the subsequent full collection will look at from-space objects:
  86   // therefore we must remove their forwarding pointers.
  87   void remove_forwarding_pointers();
  88 
  89   // Preserve the mark of "obj", if necessary, in preparation for its mark
  90   // word being overwritten with a self-forwarding-pointer.
  91   void   preserve_mark_if_necessary(oop obj, markOop m);
  92   void   preserve_mark(oop obj, markOop m);    // work routine used by the above
  93 
  94   // Together, these keep <object with a preserved mark, mark value> pairs.
  95   // They should always contain the same number of elements.
  96   Stack<oop, mtGC>     _objs_with_preserved_marks;
  97   Stack<markOop, mtGC> _preserved_marks_of_objs;
  98 
  99   // Promotion failure handling
 100   ExtendedOopClosure *_promo_failure_scan_stack_closure;
 101   void set_promo_failure_scan_stack_closure(ExtendedOopClosure *scan_stack_closure) {
 102     _promo_failure_scan_stack_closure = scan_stack_closure;
 103   }
 104 
 105   Stack<oop, mtGC> _promo_failure_scan_stack;
 106   void drain_promo_failure_scan_stack(void);
 107   bool _promo_failure_drain_in_progress;
 108 
 109   // Performance Counters
 110   GenerationCounters*  _gen_counters;
 111   CSpaceCounters*      _eden_counters;
 112   CSpaceCounters*      _from_counters;
 113   CSpaceCounters*      _to_counters;
 114 
 115   // sizing information
 116   size_t               _max_eden_size;
 117   size_t               _max_survivor_size;
 118 
 119   // Allocation support
 120   bool _should_allocate_from_space;
 121   bool should_allocate_from_space() const {
 122     return _should_allocate_from_space;
 123   }
 124   void clear_should_allocate_from_space() {
 125     _should_allocate_from_space = false;
 126   }
 127   void set_should_allocate_from_space() {
 128     _should_allocate_from_space = true;
 129   }
 130 
 131   // Tenuring
 132   void adjust_desired_tenuring_threshold();
 133 
 134   // Spaces
 135   EdenSpace*       _eden_space;
 136   ContiguousSpace* _from_space;
 137   ContiguousSpace* _to_space;
 138 
 139   STWGCTimer* _gc_timer;
 140 
 141   enum SomeProtectedConstants {
 142     // Generations are GenGrain-aligned and have size that are multiples of
 143     // GenGrain.
 144     MinFreeScratchWords = 100
 145   };
 146 
 147   // Return the size of a survivor space if this generation were of size
 148   // gen_size.
 149   size_t compute_survivor_size(size_t gen_size, size_t alignment) const {
 150     size_t n = gen_size / (SurvivorRatio + 2);
 151     return n > alignment ? align_size_down(n, alignment) : alignment;
 152   }
 153 
 154  public:  // was "protected" but caused compile error on win32
 155   class IsAliveClosure: public BoolObjectClosure {
 156     Generation* _g;
 157   public:
 158     IsAliveClosure(Generation* g);
 159     bool do_object_b(oop p);
 160   };
 161 
 162   class KeepAliveClosure: public OopClosure {
 163   protected:
 164     ScanWeakRefClosure* _cl;
 165     CardTableRS* _rs;
 166     template <class T> void do_oop_work(T* p);
 167   public:
 168     KeepAliveClosure(ScanWeakRefClosure* cl);
 169     virtual void do_oop(oop* p);
 170     virtual void do_oop(narrowOop* p);
 171   };
 172 
 173   class FastKeepAliveClosure: public KeepAliveClosure {
 174   protected:
 175     HeapWord* _boundary;
 176     template <class T> void do_oop_work(T* p);
 177   public:
 178     FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl);
 179     virtual void do_oop(oop* p);
 180     virtual void do_oop(narrowOop* p);
 181   };
 182 
 183   class EvacuateFollowersClosure: public VoidClosure {
 184     GenCollectedHeap* _gch;
 185     int _level;
 186     ScanClosure* _scan_cur_or_nonheap;
 187     ScanClosure* _scan_older;
 188   public:
 189     EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
 190                              ScanClosure* cur, ScanClosure* older);
 191     void do_void();
 192   };
 193 
 194   class FastEvacuateFollowersClosure: public VoidClosure {
 195     GenCollectedHeap* _gch;
 196     int _level;
 197     DefNewGeneration* _gen;
 198     FastScanClosure* _scan_cur_or_nonheap;
 199     FastScanClosure* _scan_older;
 200   public:
 201     FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
 202                                  DefNewGeneration* gen,
 203                                  FastScanClosure* cur,
 204                                  FastScanClosure* older);
 205     void do_void();
 206   };
 207 
 208  public:
 209   DefNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level,
 210                    const char* policy="Copy");
 211 
 212   virtual void ref_processor_init();
 213 
 214   virtual Generation::Name kind() { return Generation::DefNew; }
 215 
 216   // Accessing spaces
 217   EdenSpace*       eden() const           { return _eden_space; }
 218   ContiguousSpace* from() const           { return _from_space;  }
 219   ContiguousSpace* to()   const           { return _to_space;    }
 220 
 221   virtual CompactibleSpace* first_compaction_space() const;
 222 
 223   // Space enquiries
 224   size_t capacity() const;
 225   size_t used() const;
 226   size_t free() const;
 227   size_t max_capacity() const;
 228   size_t capacity_before_gc() const;
 229   size_t unsafe_max_alloc_nogc() const;
 230   size_t contiguous_available() const;
 231 
 232   size_t max_eden_size() const              { return _max_eden_size; }
 233   size_t max_survivor_size() const          { return _max_survivor_size; }
 234 
 235   bool supports_inline_contig_alloc() const { return true; }
 236   HeapWord** top_addr() const;
 237   HeapWord** end_addr() const;
 238 
 239   // Thread-local allocation buffers
 240   bool supports_tlab_allocation() const { return true; }
 241   size_t tlab_capacity() const;
 242   size_t unsafe_max_tlab_alloc() const;
 243 
 244   // Grow the generation by the specified number of bytes.
 245   // The size of bytes is assumed to be properly aligned.
 246   // Return true if the expansion was successful.
 247   bool expand(size_t bytes);
 248 
 249   // DefNewGeneration cannot currently expand except at
 250   // a GC.
 251   virtual bool is_maximal_no_gc() const { return true; }
 252 
 253   // Iteration
 254   void object_iterate(ObjectClosure* blk);
 255   void object_iterate_since_last_GC(ObjectClosure* cl);
 256 
 257   void younger_refs_iterate(OopsInGenClosure* cl);
 258 
 259   void space_iterate(SpaceClosure* blk, bool usedOnly = false);
 260 
 261   // Allocation support
 262   virtual bool should_allocate(size_t word_size, bool is_tlab) {
 263     assert(UseTLAB || !is_tlab, "Should not allocate tlab");
 264 
 265     size_t overflow_limit    = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);
 266 
 267     const bool non_zero      = word_size > 0;
 268     const bool overflows     = word_size >= overflow_limit;
 269     const bool check_too_big = _pretenure_size_threshold_words > 0;
 270     const bool not_too_big   = word_size < _pretenure_size_threshold_words;
 271     const bool size_ok       = is_tlab || !check_too_big || not_too_big;
 272 
 273     bool result = !overflows &&
 274                   non_zero   &&
 275                   size_ok;
 276 
 277     return result;
 278   }
 279 
 280   HeapWord* allocate(size_t word_size, bool is_tlab);
 281   HeapWord* allocate_from_space(size_t word_size);
 282 
 283   HeapWord* par_allocate(size_t word_size, bool is_tlab);
 284 
 285   // Prologue & Epilogue
 286   virtual void gc_prologue(bool full);
 287   virtual void gc_epilogue(bool full);
 288 
 289   // Save the tops for eden, from, and to
 290   virtual void record_spaces_top();
 291 
 292   // Doesn't require additional work during GC prologue and epilogue
 293   virtual bool performs_in_place_marking() const { return false; }
 294 
 295   // Accessing marks
 296   void save_marks();
 297   void reset_saved_marks();
 298   bool no_allocs_since_save_marks();
 299 
 300   // Need to declare the full complement of closures, whether we'll
 301   // override them or not, or get message from the compiler:
 302   //   oop_since_save_marks_iterate_nv hides virtual function...
 303 #define DefNew_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
 304   void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
 305 
 306   ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DECL)
 307 
 308 #undef DefNew_SINCE_SAVE_MARKS_DECL
 309 
 310   // For non-youngest collection, the DefNewGeneration can contribute
 311   // "to-space".
 312   virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor,
 313                           size_t max_alloc_words);
 314 
 315   // Reset for contribution of "to-space".
 316   virtual void reset_scratch();
 317 
 318   // GC support
 319   virtual void compute_new_size();
 320 
 321   // Returns true if the collection is likely to be safely
 322   // completed. Even if this method returns true, a collection
 323   // may not be guaranteed to succeed, and the system should be
 324   // able to safely unwind and recover from that failure, albeit
 325   // at some additional cost. Override superclass's implementation.
 326   virtual bool collection_attempt_is_safe();
 327 
 328   virtual void collect(bool   full,
 329                        bool   clear_all_soft_refs,
 330                        size_t size,
 331                        bool   is_tlab);
 332   HeapWord* expand_and_allocate(size_t size,
 333                                 bool is_tlab,
 334                                 bool parallel = false);
 335 
 336   oop copy_to_survivor_space(oop old);
 337   uint tenuring_threshold() { return _tenuring_threshold; }
 338 
 339   // Performance Counter support
 340   void update_counters();
 341 
 342   // Printing
 343   virtual const char* name() const;
 344   virtual const char* short_name() const { return "DefNew"; }
 345 
 346   bool must_be_youngest() const { return true; }
 347   bool must_be_oldest() const { return false; }
 348 
 349   // PrintHeapAtGC support.
 350   void print_on(outputStream* st) const;
 351 
 352   void verify();
 353 
 354   bool promo_failure_scan_is_complete() const {
 355     return _promo_failure_scan_stack.is_empty();
 356   }
 357 
 358  protected:
 359   // If clear_space is true, clear the survivor spaces.  Eden is
 360   // cleared if the minimum size of eden is 0.  If mangle_space
 361   // is true, also mangle the space in debug mode.
 362   void compute_space_boundaries(uintx minimum_eden_size,
 363                                 bool clear_space,
 364                                 bool mangle_space);
 365   // Scavenge support
 366   void swap_spaces();
 367 };
 368 
 369 #endif // SHARE_VM_MEMORY_DEFNEWGENERATION_HPP