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