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  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_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP
  27 
  28 #include "gc/shared/adaptiveSizePolicy.hpp"
  29 #include "gc/shared/collectedHeap.hpp"
  30 #include "gc/shared/collectorPolicy.hpp"
  31 #include "gc/shared/generation.hpp"
  32 
  33 class StrongRootsScope;
  34 class SubTasksDone;
  35 class WorkGang;
  36 
  37 // A "GenCollectedHeap" is a CollectedHeap that uses generational
  38 // collection.  It has two generations, young and old.
  39 class GenCollectedHeap : public CollectedHeap {
  40   friend class GenCollectorPolicy;
  41   friend class Generation;
  42   friend class DefNewGeneration;
  43   friend class TenuredGeneration;
  44   friend class ConcurrentMarkSweepGeneration;
  45   friend class CMSCollector;
  46   friend class GenMarkSweep;
  47   friend class VM_GenCollectForAllocation;
  48   friend class VM_GenCollectFull;
  49   friend class VM_GenCollectFullConcurrent;
  50   friend class VM_GC_HeapInspection;
  51   friend class VM_HeapDumper;
  52   friend class HeapInspection;
  53   friend class GCCauseSetter;
  54   friend class VMStructs;
  55 public:
  56   friend class VM_PopulateDumpSharedSpace;
  57 
  58 private:
  59   Generation* _young_gen;
  60   Generation* _old_gen;
  61 
  62   // The singleton Gen Remembered Set.
  63   GenRemSet* _rem_set;
  64 
  65   // The generational collector policy.
  66   GenCollectorPolicy* _gen_policy;
  67 
  68   // Indicates that the most recent previous incremental collection failed.
  69   // The flag is cleared when an action is taken that might clear the
  70   // condition that caused that incremental collection to fail.
  71   bool _incremental_collection_failed;
  72 
  73   // In support of ExplicitGCInvokesConcurrent functionality
  74   unsigned int _full_collections_completed;
  75 
  76   // Data structure for claiming the (potentially) parallel tasks in
  77   // (gen-specific) roots processing.
  78   SubTasksDone* _process_strong_tasks;
  79 
  80   // Collects the given generation.
  81   void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
  82                           bool run_verification, bool clear_soft_refs,
  83                           bool restore_marks_for_biased_locking);
  84 
  85   // In block contents verification, the number of header words to skip
  86   NOT_PRODUCT(static size_t _skip_header_HeapWords;)
  87 
  88   WorkGang* _workers;
  89 
  90 protected:
  91   // Helper functions for allocation
  92   HeapWord* attempt_allocation(size_t size,
  93                                bool   is_tlab,
  94                                bool   first_only);
  95 
  96   // Helper function for two callbacks below.
  97   // Considers collection of the first max_level+1 generations.
  98   void do_collection(bool   full,
  99                      bool   clear_all_soft_refs,
 100                      size_t size,
 101                      bool   is_tlab,
 102                      int    max_level);
 103 
 104   // Callback from VM_GenCollectForAllocation operation.
 105   // This function does everything necessary/possible to satisfy an
 106   // allocation request that failed in the youngest generation that should
 107   // have handled it (including collection, expansion, etc.)
 108   HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
 109 
 110   // Callback from VM_GenCollectFull operation.
 111   // Perform a full collection of the first max_level+1 generations.
 112   virtual void do_full_collection(bool clear_all_soft_refs);
 113   void do_full_collection(bool clear_all_soft_refs, int max_level);
 114 
 115   // Does the "cause" of GC indicate that
 116   // we absolutely __must__ clear soft refs?
 117   bool must_clear_all_soft_refs();
 118 
 119 public:
 120   GenCollectedHeap(GenCollectorPolicy *policy);
 121 
 122   WorkGang* workers() const { return _workers; }
 123 
 124   GCStats* gc_stats(int level) const;
 125 
 126   // Returns JNI_OK on success
 127   virtual jint initialize();
 128 
 129   // Reserve aligned space for the heap as needed by the contained generations.
 130   char* allocate(size_t alignment, ReservedSpace* heap_rs);
 131 
 132   // Does operations required after initialization has been done.
 133   void post_initialize();
 134 
 135   // Initialize ("weak") refs processing support
 136   virtual void ref_processing_init();
 137 
 138   virtual Name kind() const {
 139     return CollectedHeap::GenCollectedHeap;
 140   }
 141 
 142   Generation* young_gen() const { return _young_gen; }
 143   Generation* old_gen()   const { return _old_gen; }
 144 
 145   // The generational collector policy.
 146   GenCollectorPolicy* gen_policy() const { return _gen_policy; }
 147 
 148   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }
 149 
 150   // Adaptive size policy
 151   virtual AdaptiveSizePolicy* size_policy() {
 152     return gen_policy()->size_policy();
 153   }
 154 
 155   // Return the (conservative) maximum heap alignment
 156   static size_t conservative_max_heap_alignment() {
 157     return Generation::GenGrain;
 158   }
 159 
 160   size_t capacity() const;
 161   size_t used() const;
 162 
 163   // Save the "used_region" for generations level and lower.
 164   void save_used_regions(int level);
 165 
 166   size_t max_capacity() const;
 167 
 168   HeapWord* mem_allocate(size_t size,
 169                          bool*  gc_overhead_limit_was_exceeded);
 170 
 171   // We may support a shared contiguous allocation area, if the youngest
 172   // generation does.
 173   bool supports_inline_contig_alloc() const;
 174   HeapWord** top_addr() const;
 175   HeapWord** end_addr() const;
 176 
 177   // Perform a full collection of the heap; intended for use in implementing
 178   // "System.gc". This implies as full a collection as the CollectedHeap
 179   // supports. Caller does not hold the Heap_lock on entry.
 180   void collect(GCCause::Cause cause);
 181 
 182   // The same as above but assume that the caller holds the Heap_lock.
 183   void collect_locked(GCCause::Cause cause);
 184 
 185   // Perform a full collection of the first max_level+1 generations.
 186   // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
 187   void collect(GCCause::Cause cause, int max_level);
 188 
 189   // Returns "TRUE" iff "p" points into the committed areas of the heap.
 190   // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
 191   // be expensive to compute in general, so, to prevent
 192   // their inadvertent use in product jvm's, we restrict their use to
 193   // assertion checking or verification only.
 194   bool is_in(const void* p) const;
 195 
 196   // override
 197   bool is_in_closed_subset(const void* p) const {
 198     if (UseConcMarkSweepGC) {
 199       return is_in_reserved(p);
 200     } else {
 201       return is_in(p);
 202     }
 203   }
 204 
 205   // Returns true if the reference is to an object in the reserved space
 206   // for the young generation.
 207   // Assumes the the young gen address range is less than that of the old gen.
 208   bool is_in_young(oop p);
 209 
 210 #ifdef ASSERT
 211   bool is_in_partial_collection(const void* p);
 212 #endif
 213 
 214   virtual bool is_scavengable(const void* addr) {
 215     return is_in_young((oop)addr);
 216   }
 217 
 218   // Iteration functions.
 219   void oop_iterate_no_header(OopClosure* cl);
 220   void oop_iterate(ExtendedOopClosure* cl);
 221   void object_iterate(ObjectClosure* cl);
 222   void safe_object_iterate(ObjectClosure* cl);
 223   Space* space_containing(const void* addr) const;
 224 
 225   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
 226   // each address in the (reserved) heap is a member of exactly
 227   // one block.  The defining characteristic of a block is that it is
 228   // possible to find its size, and thus to progress forward to the next
 229   // block.  (Blocks may be of different sizes.)  Thus, blocks may
 230   // represent Java objects, or they might be free blocks in a
 231   // free-list-based heap (or subheap), as long as the two kinds are
 232   // distinguishable and the size of each is determinable.
 233 
 234   // Returns the address of the start of the "block" that contains the
 235   // address "addr".  We say "blocks" instead of "object" since some heaps
 236   // may not pack objects densely; a chunk may either be an object or a
 237   // non-object.
 238   virtual HeapWord* block_start(const void* addr) const;
 239 
 240   // Requires "addr" to be the start of a chunk, and returns its size.
 241   // "addr + size" is required to be the start of a new chunk, or the end
 242   // of the active area of the heap. Assumes (and verifies in non-product
 243   // builds) that addr is in the allocated part of the heap and is
 244   // the start of a chunk.
 245   virtual size_t block_size(const HeapWord* addr) const;
 246 
 247   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 248   // the block is an object. Assumes (and verifies in non-product
 249   // builds) that addr is in the allocated part of the heap and is
 250   // the start of a chunk.
 251   virtual bool block_is_obj(const HeapWord* addr) const;
 252 
 253   // Section on TLAB's.
 254   virtual bool supports_tlab_allocation() const;
 255   virtual size_t tlab_capacity(Thread* thr) const;
 256   virtual size_t tlab_used(Thread* thr) const;
 257   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
 258   virtual HeapWord* allocate_new_tlab(size_t size);
 259 
 260   // Can a compiler initialize a new object without store barriers?
 261   // This permission only extends from the creation of a new object
 262   // via a TLAB up to the first subsequent safepoint.
 263   virtual bool can_elide_tlab_store_barriers() const {
 264     return true;
 265   }
 266 
 267   virtual bool card_mark_must_follow_store() const {
 268     return UseConcMarkSweepGC;
 269   }
 270 
 271   // We don't need barriers for stores to objects in the
 272   // young gen and, a fortiori, for initializing stores to
 273   // objects therein. This applies to DefNew+Tenured and ParNew+CMS
 274   // only and may need to be re-examined in case other
 275   // kinds of collectors are implemented in the future.
 276   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
 277     return is_in_young(new_obj);
 278   }
 279 
 280   // The "requestor" generation is performing some garbage collection
 281   // action for which it would be useful to have scratch space.  The
 282   // requestor promises to allocate no more than "max_alloc_words" in any
 283   // older generation (via promotion say.)   Any blocks of space that can
 284   // be provided are returned as a list of ScratchBlocks, sorted by
 285   // decreasing size.
 286   ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
 287   // Allow each generation to reset any scratch space that it has
 288   // contributed as it needs.
 289   void release_scratch();
 290 
 291   // Ensure parsability: override
 292   virtual void ensure_parsability(bool retire_tlabs);
 293 
 294   // Time in ms since the longest time a collector ran in
 295   // in any generation.
 296   virtual jlong millis_since_last_gc();
 297 
 298   // Total number of full collections completed.
 299   unsigned int total_full_collections_completed() {
 300     assert(_full_collections_completed <= _total_full_collections,
 301            "Can't complete more collections than were started");
 302     return _full_collections_completed;
 303   }
 304 
 305   // Update above counter, as appropriate, at the end of a stop-world GC cycle
 306   unsigned int update_full_collections_completed();
 307   // Update above counter, as appropriate, at the end of a concurrent GC cycle
 308   unsigned int update_full_collections_completed(unsigned int count);
 309 
 310   // Update "time of last gc" for all generations to "now".
 311   void update_time_of_last_gc(jlong now) {
 312     _young_gen->update_time_of_last_gc(now);
 313     _old_gen->update_time_of_last_gc(now);
 314   }
 315 
 316   // Update the gc statistics for each generation.
 317   // "level" is the level of the latest collection.
 318   void update_gc_stats(int current_level, bool full) {
 319     _young_gen->update_gc_stats(current_level, full);
 320     _old_gen->update_gc_stats(current_level, full);
 321   }
 322 
 323   bool no_gc_in_progress() { return !is_gc_active(); }
 324 
 325   // Override.
 326   void prepare_for_verify();
 327 
 328   // Override.
 329   void verify(bool silent, VerifyOption option);
 330 
 331   // Override.
 332   virtual void print_on(outputStream* st) const;
 333   virtual void print_gc_threads_on(outputStream* st) const;
 334   virtual void gc_threads_do(ThreadClosure* tc) const;
 335   virtual void print_tracing_info() const;
 336   virtual void print_on_error(outputStream* st) const;
 337 
 338   // PrintGC, PrintGCDetails support
 339   void print_heap_change(size_t prev_used) const;
 340 
 341   // The functions below are helper functions that a subclass of
 342   // "CollectedHeap" can use in the implementation of its virtual
 343   // functions.
 344 
 345   class GenClosure : public StackObj {
 346    public:
 347     virtual void do_generation(Generation* gen) = 0;
 348   };
 349 
 350   // Apply "cl.do_generation" to all generations in the heap
 351   // If "old_to_young" determines the order.
 352   void generation_iterate(GenClosure* cl, bool old_to_young);
 353 
 354   // Return "true" if all generations have reached the
 355   // maximal committed limit that they can reach, without a garbage
 356   // collection.
 357   virtual bool is_maximal_no_gc() const;
 358 
 359   // This function returns the "GenRemSet" object that allows us to scan
 360   // generations in a fully generational heap.
 361   GenRemSet* rem_set() { return _rem_set; }
 362 
 363   // Convenience function to be used in situations where the heap type can be
 364   // asserted to be this type.
 365   static GenCollectedHeap* heap();
 366 
 367   // Invoke the "do_oop" method of one of the closures "not_older_gens"
 368   // or "older_gens" on root locations for the generation at
 369   // "level".  (The "older_gens" closure is used for scanning references
 370   // from older generations; "not_older_gens" is used everywhere else.)
 371   // If "younger_gens_as_roots" is false, younger generations are
 372   // not scanned as roots; in this case, the caller must be arranging to
 373   // scan the younger generations itself.  (For example, a generation might
 374   // explicitly mark reachable objects in younger generations, to avoid
 375   // excess storage retention.)
 376   // The "so" argument determines which of the roots
 377   // the closure is applied to:
 378   // "SO_None" does none;
 379   enum ScanningOption {
 380     SO_None                =  0x0,
 381     SO_AllCodeCache        =  0x8,
 382     SO_ScavengeCodeCache   = 0x10
 383   };
 384 
 385  private:
 386   void process_roots(StrongRootsScope* scope,
 387                      ScanningOption so,
 388                      OopClosure* strong_roots,
 389                      OopClosure* weak_roots,
 390                      CLDClosure* strong_cld_closure,
 391                      CLDClosure* weak_cld_closure,
 392                      CodeBlobClosure* code_roots);
 393 
 394  public:
 395   static const bool StrongAndWeakRoots = false;
 396   static const bool StrongRootsOnly    = true;
 397 
 398   void gen_process_roots(StrongRootsScope* scope,
 399                          int level,
 400                          bool younger_gens_as_roots,
 401                          ScanningOption so,
 402                          bool only_strong_roots,
 403                          OopsInGenClosure* not_older_gens,
 404                          OopsInGenClosure* older_gens,
 405                          CLDClosure* cld_closure);
 406 
 407   // Apply "root_closure" to all the weak roots of the system.
 408   // These include JNI weak roots, string table,
 409   // and referents of reachable weak refs.
 410   void gen_process_weak_roots(OopClosure* root_closure);
 411 
 412   // Set the saved marks of generations, if that makes sense.
 413   // In particular, if any generation might iterate over the oops
 414   // in other generations, it should call this method.
 415   void save_marks();
 416 
 417   // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
 418   // allocated since the last call to save_marks in generations at or above
 419   // "level".  The "cur" closure is
 420   // applied to references in the generation at "level", and the "older"
 421   // closure to older generations.
 422 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix)    \
 423   void oop_since_save_marks_iterate(int level,                          \
 424                                     OopClosureType* cur,                \
 425                                     OopClosureType* older);
 426 
 427   ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
 428 
 429 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
 430 
 431   // Returns "true" iff no allocations have occurred in any generation at
 432   // "level" or above since the last
 433   // call to "save_marks".
 434   bool no_allocs_since_save_marks(int level);
 435 
 436   // Returns true if an incremental collection is likely to fail.
 437   // We optionally consult the young gen, if asked to do so;
 438   // otherwise we base our answer on whether the previous incremental
 439   // collection attempt failed with no corrective action as of yet.
 440   bool incremental_collection_will_fail(bool consult_young) {
 441     // Assumes a 2-generation system; the first disjunct remembers if an
 442     // incremental collection failed, even when we thought (second disjunct)
 443     // that it would not.
 444     assert(heap()->collector_policy()->is_generation_policy(),
 445            "the following definition may not be suitable for an n(>2)-generation system");
 446     return incremental_collection_failed() ||
 447            (consult_young && !_young_gen->collection_attempt_is_safe());
 448   }
 449 
 450   // If a generation bails out of an incremental collection,
 451   // it sets this flag.
 452   bool incremental_collection_failed() const {
 453     return _incremental_collection_failed;
 454   }
 455   void set_incremental_collection_failed() {
 456     _incremental_collection_failed = true;
 457   }
 458   void clear_incremental_collection_failed() {
 459     _incremental_collection_failed = false;
 460   }
 461 
 462   // Promotion of obj into gen failed.  Try to promote obj to higher
 463   // gens in ascending order; return the new location of obj if successful.
 464   // Otherwise, try expand-and-allocate for obj in both the young and old
 465   // generation; return the new location of obj if successful.  Otherwise, return NULL.
 466   oop handle_failed_promotion(Generation* old_gen,
 467                               oop obj,
 468                               size_t obj_size);
 469 
 470 private:
 471   // Accessor for memory state verification support
 472   NOT_PRODUCT(
 473     static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
 474   )
 475 
 476   // Override
 477   void check_for_non_bad_heap_word_value(HeapWord* addr,
 478     size_t size) PRODUCT_RETURN;
 479 
 480   // For use by mark-sweep.  As implemented, mark-sweep-compact is global
 481   // in an essential way: compaction is performed across generations, by
 482   // iterating over spaces.
 483   void prepare_for_compaction();
 484 
 485   // Perform a full collection of the first max_level+1 generations.
 486   // This is the low level interface used by the public versions of
 487   // collect() and collect_locked(). Caller holds the Heap_lock on entry.
 488   void collect_locked(GCCause::Cause cause, int max_level);
 489 
 490   // Returns success or failure.
 491   bool create_cms_collector();
 492 
 493   // In support of ExplicitGCInvokesConcurrent functionality
 494   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 495   void collect_mostly_concurrent(GCCause::Cause cause);
 496 
 497   // Save the tops of the spaces in all generations
 498   void record_gen_tops_before_GC() PRODUCT_RETURN;
 499 
 500 protected:
 501   void gc_prologue(bool full);
 502   void gc_epilogue(bool full);
 503 };
 504 
 505 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP