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  24 
  25 #ifndef SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP
  26 #define SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP
  27 
  28 #include "gc/shared/collectedHeap.hpp"
  29 #include "gc/shared/generation.hpp"
  30 #include "gc/shared/oopStorageParState.hpp"
  31 #include "gc/shared/preGCValues.hpp"
  32 #include "gc/shared/softRefGenPolicy.hpp"
  33 
  34 class AdaptiveSizePolicy;
  35 class CardTableRS;
  36 class GCPolicyCounters;
  37 class GenerationSpec;
  38 class StrongRootsScope;
  39 class SubTasksDone;
  40 class WorkGang;
  41 
  42 // A "GenCollectedHeap" is a CollectedHeap that uses generational
  43 // collection.  It has two generations, young and old.
  44 class GenCollectedHeap : public CollectedHeap {
  45   friend class Generation;
  46   friend class DefNewGeneration;
  47   friend class TenuredGeneration;
  48   friend class GenMarkSweep;
  49   friend class VM_GenCollectForAllocation;
  50   friend class VM_GenCollectFull;
  51   friend class VM_GenCollectFullConcurrent;
  52   friend class VM_GC_HeapInspection;
  53   friend class VM_HeapDumper;
  54   friend class HeapInspection;
  55   friend class GCCauseSetter;
  56   friend class VMStructs;
  57 public:
  58   friend class VM_PopulateDumpSharedSpace;
  59 
  60   enum GenerationType {
  61     YoungGen,
  62     OldGen
  63   };
  64 
  65 protected:
  66   Generation* _young_gen;
  67   Generation* _old_gen;
  68 
  69 private:
  70   GenerationSpec* _young_gen_spec;
  71   GenerationSpec* _old_gen_spec;
  72 
  73   // The singleton CardTable Remembered Set.
  74   CardTableRS* _rem_set;
  75 
  76   SoftRefGenPolicy _soft_ref_gen_policy;
  77 
  78   // The sizing of the heap is controlled by a sizing policy.
  79   AdaptiveSizePolicy* _size_policy;
  80 
  81   GCPolicyCounters* _gc_policy_counters;
  82 
  83   // Indicates that the most recent previous incremental collection failed.
  84   // The flag is cleared when an action is taken that might clear the
  85   // condition that caused that incremental collection to fail.
  86   bool _incremental_collection_failed;
  87 
  88   // In support of ExplicitGCInvokesConcurrent functionality
  89   unsigned int _full_collections_completed;
  90 
  91   // Collects the given generation.
  92   void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
  93                           bool run_verification, bool clear_soft_refs,
  94                           bool restore_marks_for_biased_locking);
  95 
  96   // Reserve aligned space for the heap as needed by the contained generations.
  97   ReservedHeapSpace allocate(size_t alignment);
  98 
  99   // Initialize ("weak") refs processing support
 100   void ref_processing_init();
 101 
 102   PreGenGCValues get_pre_gc_values() const;
 103 
 104 protected:
 105 
 106   // The set of potentially parallel tasks in root scanning.
 107   enum GCH_strong_roots_tasks {
 108     GCH_PS_Universe_oops_do,
 109     GCH_PS_ObjectSynchronizer_oops_do,
 110     GCH_PS_OopStorageSet_oops_do,
 111     GCH_PS_ClassLoaderDataGraph_oops_do,
 112     GCH_PS_CodeCache_oops_do,
 113     AOT_ONLY(GCH_PS_aot_oops_do COMMA)
 114     GCH_PS_younger_gens,
 115     // Leave this one last.
 116     GCH_PS_NumElements
 117   };
 118 
 119   // Data structure for claiming the (potentially) parallel tasks in
 120   // (gen-specific) roots processing.
 121   SubTasksDone* _process_strong_tasks;
 122 
 123   GCMemoryManager* _young_manager;
 124   GCMemoryManager* _old_manager;
 125 
 126   // Helper functions for allocation
 127   HeapWord* attempt_allocation(size_t size,
 128                                bool   is_tlab,
 129                                bool   first_only);
 130 
 131   // Helper function for two callbacks below.
 132   // Considers collection of the first max_level+1 generations.
 133   void do_collection(bool           full,
 134                      bool           clear_all_soft_refs,
 135                      size_t         size,
 136                      bool           is_tlab,
 137                      GenerationType max_generation);
 138 
 139   // Callback from VM_GenCollectForAllocation operation.
 140   // This function does everything necessary/possible to satisfy an
 141   // allocation request that failed in the youngest generation that should
 142   // have handled it (including collection, expansion, etc.)
 143   HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
 144 
 145   // Callback from VM_GenCollectFull operation.
 146   // Perform a full collection of the first max_level+1 generations.
 147   virtual void do_full_collection(bool clear_all_soft_refs);
 148   void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
 149 
 150   // Does the "cause" of GC indicate that
 151   // we absolutely __must__ clear soft refs?
 152   bool must_clear_all_soft_refs();
 153 
 154   GenCollectedHeap(Generation::Name young,
 155                    Generation::Name old,
 156                    const char* policy_counters_name);
 157 
 158 public:
 159 
 160   // Returns JNI_OK on success
 161   virtual jint initialize();
 162   virtual CardTableRS* create_rem_set(const MemRegion& reserved_region);
 163 
 164   void initialize_size_policy(size_t init_eden_size,
 165                               size_t init_promo_size,
 166                               size_t init_survivor_size);
 167 
 168   // Does operations required after initialization has been done.
 169   void post_initialize();
 170 
 171   Generation* young_gen() const { return _young_gen; }
 172   Generation* old_gen()   const { return _old_gen; }
 173 
 174   bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
 175   bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
 176 
 177   MemRegion reserved_region() const { return _reserved; }
 178   bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
 179 
 180   GenerationSpec* young_gen_spec() const;
 181   GenerationSpec* old_gen_spec() const;
 182 
 183   virtual SoftRefPolicy* soft_ref_policy() { return &_soft_ref_gen_policy; }
 184 
 185   // Adaptive size policy
 186   virtual AdaptiveSizePolicy* size_policy() {
 187     return _size_policy;
 188   }
 189 
 190   // Performance Counter support
 191   GCPolicyCounters* counters()     { return _gc_policy_counters; }
 192 
 193   size_t capacity() const;
 194   size_t used() const;
 195 
 196   // Save the "used_region" for both generations.
 197   void save_used_regions();
 198 
 199   size_t max_capacity() const;
 200 
 201   HeapWord* mem_allocate(size_t size, bool*  gc_overhead_limit_was_exceeded);
 202 
 203   // We may support a shared contiguous allocation area, if the youngest
 204   // generation does.
 205   bool supports_inline_contig_alloc() const;
 206   HeapWord* volatile* top_addr() const;
 207   HeapWord** end_addr() const;
 208 
 209   // Perform a full collection of the heap; intended for use in implementing
 210   // "System.gc". This implies as full a collection as the CollectedHeap
 211   // supports. Caller does not hold the Heap_lock on entry.
 212   virtual void collect(GCCause::Cause cause);
 213 
 214   // The same as above but assume that the caller holds the Heap_lock.
 215   void collect_locked(GCCause::Cause cause);
 216 
 217   // Perform a full collection of generations up to and including max_generation.
 218   // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
 219   void collect(GCCause::Cause cause, GenerationType max_generation);
 220 
 221   // Returns "TRUE" iff "p" points into the committed areas of the heap.
 222   // The methods is_in() and is_in_youngest() may be expensive to compute
 223   // in general, so, to prevent their inadvertent use in product jvm's, we
 224   // restrict their use to assertion checking or verification only.
 225   bool is_in(const void* p) const;
 226 
 227   // Returns true if the reference is to an object in the reserved space
 228   // for the young generation.
 229   // Assumes the the young gen address range is less than that of the old gen.
 230   bool is_in_young(oop p);
 231 
 232 #ifdef ASSERT
 233   bool is_in_partial_collection(const void* p);
 234 #endif
 235 
 236   // Optimized nmethod scanning support routines
 237   virtual void register_nmethod(nmethod* nm);
 238   virtual void unregister_nmethod(nmethod* nm);
 239   virtual void verify_nmethod(nmethod* nm);
 240   virtual void flush_nmethod(nmethod* nm);
 241 
 242   void prune_scavengable_nmethods();
 243 
 244   // Iteration functions.
 245   void oop_iterate(OopIterateClosure* cl);
 246   void object_iterate(ObjectClosure* cl);
 247   Space* space_containing(const void* addr) const;
 248 
 249   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
 250   // each address in the (reserved) heap is a member of exactly
 251   // one block.  The defining characteristic of a block is that it is
 252   // possible to find its size, and thus to progress forward to the next
 253   // block.  (Blocks may be of different sizes.)  Thus, blocks may
 254   // represent Java objects, or they might be free blocks in a
 255   // free-list-based heap (or subheap), as long as the two kinds are
 256   // distinguishable and the size of each is determinable.
 257 
 258   // Returns the address of the start of the "block" that contains the
 259   // address "addr".  We say "blocks" instead of "object" since some heaps
 260   // may not pack objects densely; a chunk may either be an object or a
 261   // non-object.
 262   HeapWord* block_start(const void* addr) const;
 263 
 264   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 265   // the block is an object. Assumes (and verifies in non-product
 266   // builds) that addr is in the allocated part of the heap and is
 267   // the start of a chunk.
 268   bool block_is_obj(const HeapWord* addr) const;
 269 
 270   // Section on TLAB's.
 271   virtual bool supports_tlab_allocation() const;
 272   virtual size_t tlab_capacity(Thread* thr) const;
 273   virtual size_t tlab_used(Thread* thr) const;
 274   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
 275   virtual HeapWord* allocate_new_tlab(size_t min_size,
 276                                       size_t requested_size,
 277                                       size_t* actual_size);
 278 
 279   // The "requestor" generation is performing some garbage collection
 280   // action for which it would be useful to have scratch space.  The
 281   // requestor promises to allocate no more than "max_alloc_words" in any
 282   // older generation (via promotion say.)   Any blocks of space that can
 283   // be provided are returned as a list of ScratchBlocks, sorted by
 284   // decreasing size.
 285   ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
 286   // Allow each generation to reset any scratch space that it has
 287   // contributed as it needs.
 288   void release_scratch();
 289 
 290   // Ensure parsability: override
 291   virtual void ensure_parsability(bool retire_tlabs);
 292 
 293   // Total number of full collections completed.
 294   unsigned int total_full_collections_completed() {
 295     assert(_full_collections_completed <= _total_full_collections,
 296            "Can't complete more collections than were started");
 297     return _full_collections_completed;
 298   }
 299 
 300   // Update above counter, as appropriate, at the end of a stop-world GC cycle
 301   unsigned int update_full_collections_completed();
 302   // Update above counter, as appropriate, at the end of a concurrent GC cycle
 303   unsigned int update_full_collections_completed(unsigned int count);
 304 
 305   // Update the gc statistics for each generation.
 306   void update_gc_stats(Generation* current_generation, bool full) {
 307     _old_gen->update_gc_stats(current_generation, full);
 308   }
 309 
 310   bool no_gc_in_progress() { return !is_gc_active(); }
 311 
 312   // Override.
 313   void prepare_for_verify();
 314 
 315   // Override.
 316   void verify(VerifyOption option);
 317 
 318   // Override.
 319   virtual void print_on(outputStream* st) const;
 320   virtual void gc_threads_do(ThreadClosure* tc) const;
 321   virtual void print_tracing_info() const;
 322 
 323   // Used to print information about locations in the hs_err file.
 324   virtual bool print_location(outputStream* st, void* addr) const;
 325 
 326   void print_heap_change(const PreGenGCValues& pre_gc_values) const;
 327 
 328   // The functions below are helper functions that a subclass of
 329   // "CollectedHeap" can use in the implementation of its virtual
 330   // functions.
 331 
 332   class GenClosure : public StackObj {
 333    public:
 334     virtual void do_generation(Generation* gen) = 0;
 335   };
 336 
 337   // Apply "cl.do_generation" to all generations in the heap
 338   // If "old_to_young" determines the order.
 339   void generation_iterate(GenClosure* cl, bool old_to_young);
 340 
 341   // Return "true" if all generations have reached the
 342   // maximal committed limit that they can reach, without a garbage
 343   // collection.
 344   virtual bool is_maximal_no_gc() const;
 345 
 346   // This function returns the CardTableRS object that allows us to scan
 347   // generations in a fully generational heap.
 348   CardTableRS* rem_set() { return _rem_set; }
 349 
 350   // Convenience function to be used in situations where the heap type can be
 351   // asserted to be this type.
 352   static GenCollectedHeap* heap();
 353 
 354   // The ScanningOption determines which of the roots
 355   // the closure is applied to:
 356   // "SO_None" does none;
 357   enum ScanningOption {
 358     SO_None                =  0x0,
 359     SO_AllCodeCache        =  0x8,
 360     SO_ScavengeCodeCache   = 0x10
 361   };
 362 
 363  protected:
 364   void process_roots(StrongRootsScope* scope,
 365                      ScanningOption so,
 366                      OopClosure* strong_roots,
 367                      CLDClosure* strong_cld_closure,
 368                      CLDClosure* weak_cld_closure,
 369                      CodeBlobToOopClosure* code_roots);
 370 
 371   virtual void gc_prologue(bool full);
 372   virtual void gc_epilogue(bool full);
 373 
 374  public:
 375   void young_process_roots(StrongRootsScope* scope,
 376                            OopsInGenClosure* root_closure,
 377                            OopsInGenClosure* old_gen_closure,
 378                            CLDClosure* cld_closure);
 379 
 380   void full_process_roots(StrongRootsScope* scope,
 381                           bool is_adjust_phase,
 382                           ScanningOption so,
 383                           bool only_strong_roots,
 384                           OopsInGenClosure* root_closure,
 385                           CLDClosure* cld_closure);
 386 
 387   // Apply "root_closure" to all the weak roots of the system.
 388   // These include JNI weak roots, string table,
 389   // and referents of reachable weak refs.
 390   void gen_process_weak_roots(OopClosure* root_closure);
 391 
 392   // Set the saved marks of generations, if that makes sense.
 393   // In particular, if any generation might iterate over the oops
 394   // in other generations, it should call this method.
 395   void save_marks();
 396 
 397   // Returns "true" iff no allocations have occurred since the last
 398   // call to "save_marks".
 399   bool no_allocs_since_save_marks();
 400 
 401   // Returns true if an incremental collection is likely to fail.
 402   // We optionally consult the young gen, if asked to do so;
 403   // otherwise we base our answer on whether the previous incremental
 404   // collection attempt failed with no corrective action as of yet.
 405   bool incremental_collection_will_fail(bool consult_young) {
 406     // The first disjunct remembers if an incremental collection failed, even
 407     // when we thought (second disjunct) that it would not.
 408     return incremental_collection_failed() ||
 409            (consult_young && !_young_gen->collection_attempt_is_safe());
 410   }
 411 
 412   // If a generation bails out of an incremental collection,
 413   // it sets this flag.
 414   bool incremental_collection_failed() const {
 415     return _incremental_collection_failed;
 416   }
 417   void set_incremental_collection_failed() {
 418     _incremental_collection_failed = true;
 419   }
 420   void clear_incremental_collection_failed() {
 421     _incremental_collection_failed = false;
 422   }
 423 
 424   // Promotion of obj into gen failed.  Try to promote obj to higher
 425   // gens in ascending order; return the new location of obj if successful.
 426   // Otherwise, try expand-and-allocate for obj in both the young and old
 427   // generation; return the new location of obj if successful.  Otherwise, return NULL.
 428   oop handle_failed_promotion(Generation* old_gen,
 429                               oop obj,
 430                               size_t obj_size);
 431 
 432 
 433 private:
 434   // Return true if an allocation should be attempted in the older generation
 435   // if it fails in the younger generation.  Return false, otherwise.
 436   bool should_try_older_generation_allocation(size_t word_size) const;
 437 
 438   // Try to allocate space by expanding the heap.
 439   HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab);
 440 
 441   HeapWord* mem_allocate_work(size_t size,
 442                               bool is_tlab,
 443                               bool* gc_overhead_limit_was_exceeded);
 444 
 445 #if INCLUDE_SERIALGC
 446   // For use by mark-sweep.  As implemented, mark-sweep-compact is global
 447   // in an essential way: compaction is performed across generations, by
 448   // iterating over spaces.
 449   void prepare_for_compaction();
 450 #endif
 451 
 452   // Perform a full collection of the generations up to and including max_generation.
 453   // This is the low level interface used by the public versions of
 454   // collect() and collect_locked(). Caller holds the Heap_lock on entry.
 455   void collect_locked(GCCause::Cause cause, GenerationType max_generation);
 456 
 457   // Save the tops of the spaces in all generations
 458   void record_gen_tops_before_GC() PRODUCT_RETURN;
 459 
 460   // Return true if we need to perform full collection.
 461   bool should_do_full_collection(size_t size, bool full,
 462                                  bool is_tlab, GenerationType max_gen) const;
 463 };
 464 
 465 #endif // SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP