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