1 /*
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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_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP
  26 #define SHARE_VM_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/softRefGenPolicy.hpp"
  32 
  33 class AdaptiveSizePolicy;
  34 class GenerationSpec;
  35 class StrongRootsScope;
  36 class SubTasksDone;
  37 class WorkGang;
  38 
  39 // A "GenCollectedHeap" is a CollectedHeap that uses generational
  40 // collection.  It has two generations, young and old.
  41 class GenCollectedHeap : public CollectedHeap {
  42   friend class GenCollectorPolicy;
  43   friend class Generation;
  44   friend class DefNewGeneration;
  45   friend class TenuredGeneration;
  46   friend class ConcurrentMarkSweepGeneration;
  47   friend class CMSCollector;
  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 private:
  66   Generation* _young_gen;
  67   Generation* _old_gen;
  68 
  69   GenerationSpec* _young_gen_spec;
  70   GenerationSpec* _old_gen_spec;
  71 
  72   // The singleton CardTable Remembered Set.
  73   CardTableRS* _rem_set;
  74 
  75   // The generational collector policy.
  76   GenCollectorPolicy* _gen_policy;
  77 
  78   SoftRefGenPolicy _soft_ref_gen_policy;
  79 
  80   // The sizing of the heap is controlled by a sizing policy.
  81   AdaptiveSizePolicy* _size_policy;
  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   char* allocate(size_t alignment, ReservedSpace* heap_rs);
  98 
  99   // Initialize ("weak") refs processing support
 100   void ref_processing_init();
 101 
 102 protected:
 103 
 104   // The set of potentially parallel tasks in root scanning.
 105   enum GCH_strong_roots_tasks {
 106     GCH_PS_Universe_oops_do,
 107     GCH_PS_JNIHandles_oops_do,
 108     GCH_PS_ObjectSynchronizer_oops_do,
 109     GCH_PS_FlatProfiler_oops_do,
 110     GCH_PS_Management_oops_do,
 111     GCH_PS_SystemDictionary_oops_do,
 112     GCH_PS_ClassLoaderDataGraph_oops_do,
 113     GCH_PS_jvmti_oops_do,
 114     GCH_PS_CodeCache_oops_do,
 115     GCH_PS_aot_oops_do,
 116     GCH_PS_younger_gens,
 117     // Leave this one last.
 118     GCH_PS_NumElements
 119   };
 120 
 121   // Data structure for claiming the (potentially) parallel tasks in
 122   // (gen-specific) roots processing.
 123   SubTasksDone* _process_strong_tasks;
 124 
 125   GCMemoryManager* _young_manager;
 126   GCMemoryManager* _old_manager;
 127 
 128   // Helper functions for allocation
 129   HeapWord* attempt_allocation(size_t size,
 130                                bool   is_tlab,
 131                                bool   first_only);
 132 
 133   // Helper function for two callbacks below.
 134   // Considers collection of the first max_level+1 generations.
 135   void do_collection(bool           full,
 136                      bool           clear_all_soft_refs,
 137                      size_t         size,
 138                      bool           is_tlab,
 139                      GenerationType max_generation);
 140 
 141   // Callback from VM_GenCollectForAllocation operation.
 142   // This function does everything necessary/possible to satisfy an
 143   // allocation request that failed in the youngest generation that should
 144   // have handled it (including collection, expansion, etc.)
 145   HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
 146 
 147   // Callback from VM_GenCollectFull operation.
 148   // Perform a full collection of the first max_level+1 generations.
 149   virtual void do_full_collection(bool clear_all_soft_refs);
 150   void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
 151 
 152   // Does the "cause" of GC indicate that
 153   // we absolutely __must__ clear soft refs?
 154   bool must_clear_all_soft_refs();
 155 
 156   GenCollectedHeap(GenCollectorPolicy *policy,
 157                    Generation::Name young,
 158                    Generation::Name old);
 159 
 160   virtual void check_gen_kinds() = 0;
 161 
 162 public:
 163 
 164   // Returns JNI_OK on success
 165   virtual jint initialize();
 166 
 167   void initialize_generations(Generation::Name young,
 168                               Generation::Name old);
 169 
 170   void initialize_size_policy(size_t init_eden_size,
 171                               size_t init_promo_size,
 172                               size_t init_survivor_size);
 173 
 174   // Does operations required after initialization has been done.
 175   void post_initialize();
 176 
 177   Generation* young_gen() const { return _young_gen; }
 178   Generation* old_gen()   const { return _old_gen; }
 179 
 180   bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
 181   bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
 182 
 183   GenerationSpec* young_gen_spec() const;
 184   GenerationSpec* old_gen_spec() const;
 185 
 186   // The generational collector policy.
 187   GenCollectorPolicy* gen_policy() const { return _gen_policy; }
 188 
 189   virtual CollectorPolicy* collector_policy() const { return gen_policy(); }
 190 
 191   virtual SoftRefPolicy* soft_ref_policy() { return &_soft_ref_gen_policy; }
 192 
 193   // Adaptive size policy
 194   virtual AdaptiveSizePolicy* size_policy() {
 195     return _size_policy;
 196   }
 197 
 198   // Return the (conservative) maximum heap alignment
 199   static size_t conservative_max_heap_alignment() {
 200     return Generation::GenGrain;
 201   }
 202 
 203   size_t capacity() const;
 204   size_t used() const;
 205 
 206   // Save the "used_region" for both generations.
 207   void save_used_regions();
 208 
 209   size_t max_capacity() const;
 210 
 211   HeapWord* mem_allocate(size_t size, bool*  gc_overhead_limit_was_exceeded);
 212 
 213   // We may support a shared contiguous allocation area, if the youngest
 214   // generation does.
 215   bool supports_inline_contig_alloc() const;
 216   HeapWord* volatile* top_addr() const;
 217   HeapWord** end_addr() const;
 218 
 219   // Perform a full collection of the heap; intended for use in implementing
 220   // "System.gc". This implies as full a collection as the CollectedHeap
 221   // supports. Caller does not hold the Heap_lock on entry.
 222   virtual void collect(GCCause::Cause cause);
 223 
 224   // The same as above but assume that the caller holds the Heap_lock.
 225   void collect_locked(GCCause::Cause cause);
 226 
 227   // Perform a full collection of generations up to and including max_generation.
 228   // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
 229   void collect(GCCause::Cause cause, GenerationType max_generation);
 230 
 231   // Returns "TRUE" iff "p" points into the committed areas of the heap.
 232   // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
 233   // be expensive to compute in general, so, to prevent
 234   // their inadvertent use in product jvm's, we restrict their use to
 235   // assertion checking or verification only.
 236   bool is_in(const void* p) const;
 237 
 238   // Returns true if the reference is to an object in the reserved space
 239   // for the young generation.
 240   // Assumes the the young gen address range is less than that of the old gen.
 241   bool is_in_young(oop p);
 242 
 243 #ifdef ASSERT
 244   bool is_in_partial_collection(const void* p);
 245 #endif
 246 
 247   virtual bool is_scavengable(oop obj) {
 248     return is_in_young(obj);
 249   }
 250 
 251   // Optimized nmethod scanning support routines
 252   virtual void register_nmethod(nmethod* nm);
 253   virtual void verify_nmethod(nmethod* nmethod);
 254 
 255   // Iteration functions.
 256   void oop_iterate_no_header(OopClosure* cl);
 257   void oop_iterate(ExtendedOopClosure* cl);
 258   void object_iterate(ObjectClosure* cl);
 259   void safe_object_iterate(ObjectClosure* cl);
 260   Space* space_containing(const void* addr) const;
 261 
 262   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
 263   // each address in the (reserved) heap is a member of exactly
 264   // one block.  The defining characteristic of a block is that it is
 265   // possible to find its size, and thus to progress forward to the next
 266   // block.  (Blocks may be of different sizes.)  Thus, blocks may
 267   // represent Java objects, or they might be free blocks in a
 268   // free-list-based heap (or subheap), as long as the two kinds are
 269   // distinguishable and the size of each is determinable.
 270 
 271   // Returns the address of the start of the "block" that contains the
 272   // address "addr".  We say "blocks" instead of "object" since some heaps
 273   // may not pack objects densely; a chunk may either be an object or a
 274   // non-object.
 275   virtual HeapWord* block_start(const void* addr) const;
 276 
 277   // Requires "addr" to be the start of a chunk, and returns its size.
 278   // "addr + size" is required to be the start of a new chunk, or the end
 279   // of the active area of the heap. Assumes (and verifies in non-product
 280   // builds) that addr is in the allocated part of the heap and is
 281   // the start of a chunk.
 282   virtual size_t block_size(const HeapWord* addr) const;
 283 
 284   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 285   // the block is an object. Assumes (and verifies in non-product
 286   // builds) that addr is in the allocated part of the heap and is
 287   // the start of a chunk.
 288   virtual bool block_is_obj(const HeapWord* addr) const;
 289 
 290   // Section on TLAB's.
 291   virtual bool supports_tlab_allocation() const;
 292   virtual size_t tlab_capacity(Thread* thr) const;
 293   virtual size_t tlab_used(Thread* thr) const;
 294   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
 295   virtual HeapWord* allocate_new_tlab(size_t size);
 296 
 297   // The "requestor" generation is performing some garbage collection
 298   // action for which it would be useful to have scratch space.  The
 299   // requestor promises to allocate no more than "max_alloc_words" in any
 300   // older generation (via promotion say.)   Any blocks of space that can
 301   // be provided are returned as a list of ScratchBlocks, sorted by
 302   // decreasing size.
 303   ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
 304   // Allow each generation to reset any scratch space that it has
 305   // contributed as it needs.
 306   void release_scratch();
 307 
 308   // Ensure parsability: override
 309   virtual void ensure_parsability(bool retire_tlabs);
 310 
 311   // Time in ms since the longest time a collector ran in
 312   // in any generation.
 313   virtual jlong millis_since_last_gc();
 314 
 315   // Total number of full collections completed.
 316   unsigned int total_full_collections_completed() {
 317     assert(_full_collections_completed <= _total_full_collections,
 318            "Can't complete more collections than were started");
 319     return _full_collections_completed;
 320   }
 321 
 322   // Update above counter, as appropriate, at the end of a stop-world GC cycle
 323   unsigned int update_full_collections_completed();
 324   // Update above counter, as appropriate, at the end of a concurrent GC cycle
 325   unsigned int update_full_collections_completed(unsigned int count);
 326 
 327   // Update "time of last gc" for all generations to "now".
 328   void update_time_of_last_gc(jlong now) {
 329     _young_gen->update_time_of_last_gc(now);
 330     _old_gen->update_time_of_last_gc(now);
 331   }
 332 
 333   // Update the gc statistics for each generation.
 334   void update_gc_stats(Generation* current_generation, bool full) {
 335     _old_gen->update_gc_stats(current_generation, full);
 336   }
 337 
 338   bool no_gc_in_progress() { return !is_gc_active(); }
 339 
 340   // Override.
 341   void prepare_for_verify();
 342 
 343   // Override.
 344   void verify(VerifyOption option);
 345 
 346   // Override.
 347   virtual void print_on(outputStream* st) const;
 348   virtual void print_gc_threads_on(outputStream* st) const;
 349   virtual void gc_threads_do(ThreadClosure* tc) const;
 350   virtual void print_tracing_info() const;
 351 
 352   void print_heap_change(size_t young_prev_used, size_t old_prev_used) const;
 353 
 354   // The functions below are helper functions that a subclass of
 355   // "CollectedHeap" can use in the implementation of its virtual
 356   // functions.
 357 
 358   class GenClosure : public StackObj {
 359    public:
 360     virtual void do_generation(Generation* gen) = 0;
 361   };
 362 
 363   // Apply "cl.do_generation" to all generations in the heap
 364   // If "old_to_young" determines the order.
 365   void generation_iterate(GenClosure* cl, bool old_to_young);
 366 
 367   // Return "true" if all generations have reached the
 368   // maximal committed limit that they can reach, without a garbage
 369   // collection.
 370   virtual bool is_maximal_no_gc() const;
 371 
 372   // This function returns the CardTableRS object that allows us to scan
 373   // generations in a fully generational heap.
 374   CardTableRS* rem_set() { return _rem_set; }
 375 
 376   // Convenience function to be used in situations where the heap type can be
 377   // asserted to be this type.
 378   static GenCollectedHeap* heap();
 379 
 380   // The ScanningOption determines which of the roots
 381   // the closure is applied to:
 382   // "SO_None" does none;
 383   enum ScanningOption {
 384     SO_None                =  0x0,
 385     SO_AllCodeCache        =  0x8,
 386     SO_ScavengeCodeCache   = 0x10
 387   };
 388 
 389  protected:
 390   void process_roots(StrongRootsScope* scope,
 391                      ScanningOption so,
 392                      OopClosure* strong_roots,
 393                      OopClosure* weak_roots,
 394                      CLDClosure* strong_cld_closure,
 395                      CLDClosure* weak_cld_closure,
 396                      CodeBlobToOopClosure* code_roots);
 397 
 398   void process_string_table_roots(StrongRootsScope* scope,
 399                                   OopClosure* root_closure);
 400 
 401   // Accessor for memory state verification support
 402   NOT_PRODUCT(
 403     virtual size_t skip_header_HeapWords() { return 0; }
 404   )
 405 
 406   virtual void gc_prologue(bool full);
 407   virtual void gc_epilogue(bool full);
 408 
 409  public:
 410   void young_process_roots(StrongRootsScope* scope,
 411                            OopsInGenClosure* root_closure,
 412                            OopsInGenClosure* old_gen_closure,
 413                            CLDClosure* cld_closure);
 414 
 415   void full_process_roots(StrongRootsScope* scope,
 416                           bool is_adjust_phase,
 417                           ScanningOption so,
 418                           bool only_strong_roots,
 419                           OopsInGenClosure* root_closure,
 420                           CLDClosure* cld_closure);
 421 
 422   // Apply "root_closure" to all the weak roots of the system.
 423   // These include JNI weak roots, string table,
 424   // and referents of reachable weak refs.
 425   void gen_process_weak_roots(OopClosure* root_closure);
 426 
 427   // Set the saved marks of generations, if that makes sense.
 428   // In particular, if any generation might iterate over the oops
 429   // in other generations, it should call this method.
 430   void save_marks();
 431 
 432   // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
 433   // allocated since the last call to save_marks in generations at or above
 434   // "level".  The "cur" closure is
 435   // applied to references in the generation at "level", and the "older"
 436   // closure to older generations.
 437 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix)    \
 438   void oop_since_save_marks_iterate(GenerationType start_gen,           \
 439                                     OopClosureType* cur,                \
 440                                     OopClosureType* older);
 441 
 442   ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
 443 
 444 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
 445 
 446   // Returns "true" iff no allocations have occurred since the last
 447   // call to "save_marks".
 448   bool no_allocs_since_save_marks();
 449 
 450   // Returns true if an incremental collection is likely to fail.
 451   // We optionally consult the young gen, if asked to do so;
 452   // otherwise we base our answer on whether the previous incremental
 453   // collection attempt failed with no corrective action as of yet.
 454   bool incremental_collection_will_fail(bool consult_young) {
 455     // The first disjunct remembers if an incremental collection failed, even
 456     // when we thought (second disjunct) that it would not.
 457     return incremental_collection_failed() ||
 458            (consult_young && !_young_gen->collection_attempt_is_safe());
 459   }
 460 
 461   // If a generation bails out of an incremental collection,
 462   // it sets this flag.
 463   bool incremental_collection_failed() const {
 464     return _incremental_collection_failed;
 465   }
 466   void set_incremental_collection_failed() {
 467     _incremental_collection_failed = true;
 468   }
 469   void clear_incremental_collection_failed() {
 470     _incremental_collection_failed = false;
 471   }
 472 
 473   // Promotion of obj into gen failed.  Try to promote obj to higher
 474   // gens in ascending order; return the new location of obj if successful.
 475   // Otherwise, try expand-and-allocate for obj in both the young and old
 476   // generation; return the new location of obj if successful.  Otherwise, return NULL.
 477   oop handle_failed_promotion(Generation* old_gen,
 478                               oop obj,
 479                               size_t obj_size);
 480 
 481 
 482 private:
 483   // Return true if an allocation should be attempted in the older generation
 484   // if it fails in the younger generation.  Return false, otherwise.
 485   bool should_try_older_generation_allocation(size_t word_size) const;
 486 
 487   // Try to allocate space by expanding the heap.
 488   HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab);
 489 
 490   HeapWord* mem_allocate_work(size_t size,
 491                               bool is_tlab,
 492                               bool* gc_overhead_limit_was_exceeded);
 493 
 494   // Override
 495   void check_for_non_bad_heap_word_value(HeapWord* addr,
 496     size_t size) PRODUCT_RETURN;
 497 
 498   // For use by mark-sweep.  As implemented, mark-sweep-compact is global
 499   // in an essential way: compaction is performed across generations, by
 500   // iterating over spaces.
 501   void prepare_for_compaction();
 502 
 503   // Perform a full collection of the generations up to and including max_generation.
 504   // This is the low level interface used by the public versions of
 505   // collect() and collect_locked(). Caller holds the Heap_lock on entry.
 506   void collect_locked(GCCause::Cause cause, GenerationType max_generation);
 507 
 508   // Save the tops of the spaces in all generations
 509   void record_gen_tops_before_GC() PRODUCT_RETURN;
 510 };
 511 
 512 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP