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