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_MEMORY_GENCOLLECTEDHEAP_HPP
  26 #define SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP
  27 
  28 #include "gc_implementation/shared/adaptiveSizePolicy.hpp"
  29 #include "gc_interface/collectedHeap.hpp"
  30 #include "memory/collectorPolicy.hpp"
  31 #include "memory/generation.hpp"
  32 
  33 class SubTasksDone;
  34 class FlexibleWorkGang;
  35 
  36 // A "GenCollectedHeap" is a CollectedHeap that uses generational
  37 // collection.  It has two generations, young and old.
  38 class GenCollectedHeap : public CollectedHeap {
  39   friend class GenCollectorPolicy;
  40   friend class Generation;
  41   friend class DefNewGeneration;
  42   friend class TenuredGeneration;
  43   friend class ConcurrentMarkSweepGeneration;
  44   friend class CMSCollector;
  45   friend class GenMarkSweep;
  46   friend class VM_GenCollectForAllocation;
  47   friend class VM_GenCollectFull;
  48   friend class VM_GenCollectFullConcurrent;
  49   friend class VM_GC_HeapInspection;
  50   friend class VM_HeapDumper;
  51   friend class HeapInspection;
  52   friend class GCCauseSetter;
  53   friend class VMStructs;
  54 public:
  55   friend class VM_PopulateDumpSharedSpace;
  56 
  57  protected:
  58   // Fields:
  59   static GenCollectedHeap* _gch;
  60 
  61  private:
  62   Generation* _young_gen;
  63   Generation* _old_gen;
  64 
  65   // The singleton Gen Remembered Set.
  66   GenRemSet* _rem_set;
  67 
  68   // The generational collector policy.
  69   GenCollectorPolicy* _gen_policy;
  70 
  71   // Indicates that the most recent previous incremental collection failed.
  72   // The flag is cleared when an action is taken that might clear the
  73   // condition that caused that incremental collection to fail.
  74   bool _incremental_collection_failed;
  75 
  76   // In support of ExplicitGCInvokesConcurrent functionality
  77   unsigned int _full_collections_completed;
  78 
  79   // Data structure for claiming the (potentially) parallel tasks in
  80   // (gen-specific) roots processing.
  81   SubTasksDone* _process_strong_tasks;
  82 
  83   // Collects the given generation.
  84   void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
  85                           bool run_verification, bool clear_soft_refs,
  86                           bool restore_marks_for_biased_locking);
  87 
  88   // In block contents verification, the number of header words to skip
  89   NOT_PRODUCT(static size_t _skip_header_HeapWords;)
  90 
  91   FlexibleWorkGang* _workers;
  92 
  93 protected:
  94   // Helper functions for allocation
  95   HeapWord* attempt_allocation(size_t size,
  96                                bool   is_tlab,
  97                                bool   first_only);
  98 
  99   // Helper function for two callbacks below.
 100   // Considers collection of the first max_level+1 generations.
 101   void do_collection(bool   full,
 102                      bool   clear_all_soft_refs,
 103                      size_t size,
 104                      bool   is_tlab,
 105                      int    max_level);
 106 
 107   // Callback from VM_GenCollectForAllocation operation.
 108   // This function does everything necessary/possible to satisfy an
 109   // allocation request that failed in the youngest generation that should
 110   // have handled it (including collection, expansion, etc.)
 111   HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
 112 
 113   // Callback from VM_GenCollectFull operation.
 114   // Perform a full collection of the first max_level+1 generations.
 115   virtual void do_full_collection(bool clear_all_soft_refs);
 116   void do_full_collection(bool clear_all_soft_refs, int max_level);
 117 
 118   // Does the "cause" of GC indicate that
 119   // we absolutely __must__ clear soft refs?
 120   bool must_clear_all_soft_refs();
 121 
 122 public:
 123   GenCollectedHeap(GenCollectorPolicy *policy);
 124 
 125   FlexibleWorkGang* workers() const { return _workers; }
 126 
 127   GCStats* gc_stats(int level) const;
 128 
 129   // Returns JNI_OK on success
 130   virtual jint initialize();
 131 
 132   // Reserve aligned space for the heap as needed by the contained generations.
 133   char* allocate(size_t alignment, ReservedSpace* heap_rs);
 134 
 135   // Does operations required after initialization has been done.
 136   void post_initialize();
 137 
 138   // Initialize ("weak") refs processing support
 139   virtual void ref_processing_init();
 140 
 141   virtual Name kind() const {
 142     return CollectedHeap::GenCollectedHeap;
 143   }
 144 
 145   Generation* young_gen() const { return _young_gen; }
 146   Generation* old_gen()   const { return _old_gen; }
 147 
 148   // The generational collector policy.
 149   GenCollectorPolicy* gen_policy() const { return _gen_policy; }
 150 
 151   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }
 152 
 153   // Adaptive size policy
 154   virtual AdaptiveSizePolicy* size_policy() {
 155     return gen_policy()->size_policy();
 156   }
 157 
 158   // Return the (conservative) maximum heap alignment
 159   static size_t conservative_max_heap_alignment() {
 160     return Generation::GenGrain;
 161   }
 162 
 163   size_t capacity() const;
 164   size_t used() const;
 165 
 166   // Save the "used_region" for generations level and lower.
 167   void save_used_regions(int level);
 168 
 169   size_t max_capacity() const;
 170 
 171   HeapWord* mem_allocate(size_t size,
 172                          bool*  gc_overhead_limit_was_exceeded);
 173 
 174   // We may support a shared contiguous allocation area, if the youngest
 175   // generation does.
 176   bool supports_inline_contig_alloc() const;
 177   HeapWord** top_addr() const;
 178   HeapWord** end_addr() const;
 179 
 180   // Perform a full collection of the heap; intended for use in implementing
 181   // "System.gc". This implies as full a collection as the CollectedHeap
 182   // supports. Caller does not hold the Heap_lock on entry.
 183   void collect(GCCause::Cause cause);
 184 
 185   // The same as above but assume that the caller holds the Heap_lock.
 186   void collect_locked(GCCause::Cause cause);
 187 
 188   // Perform a full collection of the first max_level+1 generations.
 189   // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
 190   void collect(GCCause::Cause cause, int max_level);
 191 
 192   // Returns "TRUE" iff "p" points into the committed areas of the heap.
 193   // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
 194   // be expensive to compute in general, so, to prevent
 195   // their inadvertent use in product jvm's, we restrict their use to
 196   // assertion checking or verification only.
 197   bool is_in(const void* p) const;
 198 
 199   // override
 200   bool is_in_closed_subset(const void* p) const {
 201     if (UseConcMarkSweepGC) {
 202       return is_in_reserved(p);
 203     } else {
 204       return is_in(p);
 205     }
 206   }
 207 
 208   // Returns true if the reference is to an object in the reserved space
 209   // for the young generation.
 210   // Assumes the the young gen address range is less than that of the old gen.
 211   bool is_in_young(oop p);
 212 
 213 #ifdef ASSERT
 214   bool is_in_partial_collection(const void* p);
 215 #endif
 216 
 217   virtual bool is_scavengable(const void* addr) {
 218     return is_in_young((oop)addr);
 219   }
 220 
 221   // Iteration functions.
 222   void oop_iterate_no_header(OopClosure* cl);
 223   void oop_iterate(ExtendedOopClosure* cl);
 224   void object_iterate(ObjectClosure* cl);
 225   void safe_object_iterate(ObjectClosure* cl);
 226   Space* space_containing(const void* addr) const;
 227 
 228   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
 229   // each address in the (reserved) heap is a member of exactly
 230   // one block.  The defining characteristic of a block is that it is
 231   // possible to find its size, and thus to progress forward to the next
 232   // block.  (Blocks may be of different sizes.)  Thus, blocks may
 233   // represent Java objects, or they might be free blocks in a
 234   // free-list-based heap (or subheap), as long as the two kinds are
 235   // distinguishable and the size of each is determinable.
 236 
 237   // Returns the address of the start of the "block" that contains the
 238   // address "addr".  We say "blocks" instead of "object" since some heaps
 239   // may not pack objects densely; a chunk may either be an object or a
 240   // non-object.
 241   virtual HeapWord* block_start(const void* addr) const;
 242 
 243   // Requires "addr" to be the start of a chunk, and returns its size.
 244   // "addr + size" is required to be the start of a new chunk, or the end
 245   // of the active area of the heap. Assumes (and verifies in non-product
 246   // builds) that addr is in the allocated part of the heap and is
 247   // the start of a chunk.
 248   virtual size_t block_size(const HeapWord* addr) const;
 249 
 250   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 251   // the block is an object. Assumes (and verifies in non-product
 252   // builds) that addr is in the allocated part of the heap and is
 253   // the start of a chunk.
 254   virtual bool block_is_obj(const HeapWord* addr) const;
 255 
 256   // Section on TLAB's.
 257   virtual bool supports_tlab_allocation() const;
 258   virtual size_t tlab_capacity(Thread* thr) const;
 259   virtual size_t tlab_used(Thread* thr) const;
 260   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
 261   virtual HeapWord* allocate_new_tlab(size_t size);
 262 
 263   // Can a compiler initialize a new object without store barriers?
 264   // This permission only extends from the creation of a new object
 265   // via a TLAB up to the first subsequent safepoint.
 266   virtual bool can_elide_tlab_store_barriers() const {
 267     return true;
 268   }
 269 
 270   virtual bool card_mark_must_follow_store() const {
 271     return UseConcMarkSweepGC;
 272   }
 273 
 274   // We don't need barriers for stores to objects in the
 275   // young gen and, a fortiori, for initializing stores to
 276   // objects therein. This applies to DefNew+Tenured and ParNew+CMS
 277   // only and may need to be re-examined in case other
 278   // kinds of collectors are implemented in the future.
 279   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
 280     // We wanted to assert that:-
 281     // assert(UseSerialGC || UseConcMarkSweepGC,
 282     //       "Check can_elide_initializing_store_barrier() for this collector");
 283     // but unfortunately the flag UseSerialGC need not necessarily always
 284     // be set when DefNew+Tenured are being used.
 285     return is_in_young(new_obj);
 286   }
 287 
 288   // The "requestor" generation is performing some garbage collection
 289   // action for which it would be useful to have scratch space.  The
 290   // requestor promises to allocate no more than "max_alloc_words" in any
 291   // older generation (via promotion say.)   Any blocks of space that can
 292   // be provided are returned as a list of ScratchBlocks, sorted by
 293   // decreasing size.
 294   ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
 295   // Allow each generation to reset any scratch space that it has
 296   // contributed as it needs.
 297   void release_scratch();
 298 
 299   // Ensure parsability: override
 300   virtual void ensure_parsability(bool retire_tlabs);
 301 
 302   // Time in ms since the longest time a collector ran in
 303   // in any generation.
 304   virtual jlong millis_since_last_gc();
 305 
 306   // Total number of full collections completed.
 307   unsigned int total_full_collections_completed() {
 308     assert(_full_collections_completed <= _total_full_collections,
 309            "Can't complete more collections than were started");
 310     return _full_collections_completed;
 311   }
 312 
 313   // Update above counter, as appropriate, at the end of a stop-world GC cycle
 314   unsigned int update_full_collections_completed();
 315   // Update above counter, as appropriate, at the end of a concurrent GC cycle
 316   unsigned int update_full_collections_completed(unsigned int count);
 317 
 318   // Update "time of last gc" for all generations to "now".
 319   void update_time_of_last_gc(jlong now) {
 320     _young_gen->update_time_of_last_gc(now);
 321     _old_gen->update_time_of_last_gc(now);
 322   }
 323 
 324   // Update the gc statistics for each generation.
 325   // "level" is the level of the latest collection.
 326   void update_gc_stats(int current_level, bool full) {
 327     _young_gen->update_gc_stats(current_level, full);
 328     _old_gen->update_gc_stats(current_level, full);
 329   }
 330 
 331   bool no_gc_in_progress() { return !is_gc_active(); }
 332 
 333   // Override.
 334   void prepare_for_verify();
 335 
 336   // Override.
 337   void verify(bool silent, VerifyOption option);
 338 
 339   // Override.
 340   virtual void print_on(outputStream* st) const;
 341   virtual void print_gc_threads_on(outputStream* st) const;
 342   virtual void gc_threads_do(ThreadClosure* tc) const;
 343   virtual void print_tracing_info() const;
 344   virtual void print_on_error(outputStream* st) const;
 345 
 346   // PrintGC, PrintGCDetails support
 347   void print_heap_change(size_t prev_used) const;
 348 
 349   // The functions below are helper functions that a subclass of
 350   // "CollectedHeap" can use in the implementation of its virtual
 351   // functions.
 352 
 353   class GenClosure : public StackObj {
 354    public:
 355     virtual void do_generation(Generation* gen) = 0;
 356   };
 357 
 358   // Apply "cl.do_generation" to all generations in the heap
 359   // If "old_to_young" determines the order.
 360   void generation_iterate(GenClosure* cl, bool old_to_young);
 361 
 362   // Return "true" if all generations have reached the
 363   // maximal committed limit that they can reach, without a garbage
 364   // collection.
 365   virtual bool is_maximal_no_gc() const;
 366 
 367   // This function returns the "GenRemSet" object that allows us to scan
 368   // generations in a fully generational heap.
 369   GenRemSet* rem_set() { return _rem_set; }
 370 
 371   // Convenience function to be used in situations where the heap type can be
 372   // asserted to be this type.
 373   static GenCollectedHeap* heap();
 374 
 375   void set_par_threads(uint t);
 376   void set_n_termination(uint t);
 377 
 378   // Invoke the "do_oop" method of one of the closures "not_older_gens"
 379   // or "older_gens" on root locations for the generation at
 380   // "level".  (The "older_gens" closure is used for scanning references
 381   // from older generations; "not_older_gens" is used everywhere else.)
 382   // If "younger_gens_as_roots" is false, younger generations are
 383   // not scanned as roots; in this case, the caller must be arranging to
 384   // scan the younger generations itself.  (For example, a generation might
 385   // explicitly mark reachable objects in younger generations, to avoid
 386   // excess storage retention.)
 387   // The "so" argument determines which of the roots
 388   // the closure is applied to:
 389   // "SO_None" does none;
 390   enum ScanningOption {
 391     SO_None                =  0x0,
 392     SO_AllCodeCache        =  0x8,
 393     SO_ScavengeCodeCache   = 0x10
 394   };
 395 
 396  private:
 397   void process_roots(bool activate_scope,
 398                      ScanningOption so,
 399                      OopClosure* strong_roots,
 400                      OopClosure* weak_roots,
 401                      CLDClosure* strong_cld_closure,
 402                      CLDClosure* weak_cld_closure,
 403                      CodeBlobClosure* code_roots);
 404 
 405   void gen_process_roots(int level,
 406                          bool younger_gens_as_roots,
 407                          bool activate_scope,
 408                          ScanningOption so,
 409                          OopsInGenClosure* not_older_gens,
 410                          OopsInGenClosure* weak_roots,
 411                          OopsInGenClosure* older_gens,
 412                          CLDClosure* cld_closure,
 413                          CLDClosure* weak_cld_closure,
 414                          CodeBlobClosure* code_closure);
 415 
 416  public:
 417   static const bool StrongAndWeakRoots = false;
 418   static const bool StrongRootsOnly    = true;
 419 
 420   void gen_process_roots(int level,
 421                          bool younger_gens_as_roots,
 422                          bool activate_scope,
 423                          ScanningOption so,
 424                          bool only_strong_roots,
 425                          OopsInGenClosure* not_older_gens,
 426                          OopsInGenClosure* older_gens,
 427                          CLDClosure* cld_closure);
 428 
 429   // Apply "root_closure" to all the weak roots of the system.
 430   // These include JNI weak roots, string table,
 431   // and referents of reachable weak refs.
 432   void gen_process_weak_roots(OopClosure* root_closure);
 433 
 434   // Set the saved marks of generations, if that makes sense.
 435   // In particular, if any generation might iterate over the oops
 436   // in other generations, it should call this method.
 437   void save_marks();
 438 
 439   // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
 440   // allocated since the last call to save_marks in generations at or above
 441   // "level".  The "cur" closure is
 442   // applied to references in the generation at "level", and the "older"
 443   // closure to older generations.
 444 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix)    \
 445   void oop_since_save_marks_iterate(int level,                          \
 446                                     OopClosureType* cur,                \
 447                                     OopClosureType* older);
 448 
 449   ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
 450 
 451 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
 452 
 453   // Returns "true" iff no allocations have occurred in any generation at
 454   // "level" or above since the last
 455   // call to "save_marks".
 456   bool no_allocs_since_save_marks(int level);
 457 
 458   // Returns true if an incremental collection is likely to fail.
 459   // We optionally consult the young gen, if asked to do so;
 460   // otherwise we base our answer on whether the previous incremental
 461   // collection attempt failed with no corrective action as of yet.
 462   bool incremental_collection_will_fail(bool consult_young) {
 463     // Assumes a 2-generation system; the first disjunct remembers if an
 464     // incremental collection failed, even when we thought (second disjunct)
 465     // that it would not.
 466     assert(heap()->collector_policy()->is_generation_policy(),
 467            "the following definition may not be suitable for an n(>2)-generation system");
 468     return incremental_collection_failed() ||
 469            (consult_young && !_young_gen->collection_attempt_is_safe());
 470   }
 471 
 472   // If a generation bails out of an incremental collection,
 473   // it sets this flag.
 474   bool incremental_collection_failed() const {
 475     return _incremental_collection_failed;
 476   }
 477   void set_incremental_collection_failed() {
 478     _incremental_collection_failed = true;
 479   }
 480   void clear_incremental_collection_failed() {
 481     _incremental_collection_failed = false;
 482   }
 483 
 484   // Promotion of obj into gen failed.  Try to promote obj to higher
 485   // gens in ascending order; return the new location of obj if successful.
 486   // Otherwise, try expand-and-allocate for obj in both the young and old
 487   // generation; return the new location of obj if successful.  Otherwise, return NULL.
 488   oop handle_failed_promotion(Generation* old_gen,
 489                               oop obj,
 490                               size_t obj_size);
 491 
 492 private:
 493   // Accessor for memory state verification support
 494   NOT_PRODUCT(
 495     static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
 496   )
 497 
 498   // Override
 499   void check_for_non_bad_heap_word_value(HeapWord* addr,
 500     size_t size) PRODUCT_RETURN;
 501 
 502   // For use by mark-sweep.  As implemented, mark-sweep-compact is global
 503   // in an essential way: compaction is performed across generations, by
 504   // iterating over spaces.
 505   void prepare_for_compaction();
 506 
 507   // Perform a full collection of the first max_level+1 generations.
 508   // This is the low level interface used by the public versions of
 509   // collect() and collect_locked(). Caller holds the Heap_lock on entry.
 510   void collect_locked(GCCause::Cause cause, int max_level);
 511 
 512   // Returns success or failure.
 513   bool create_cms_collector();
 514 
 515   // In support of ExplicitGCInvokesConcurrent functionality
 516   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 517   void collect_mostly_concurrent(GCCause::Cause cause);
 518 
 519   // Save the tops of the spaces in all generations
 520   void record_gen_tops_before_GC() PRODUCT_RETURN;
 521 
 522 protected:
 523   void gc_prologue(bool full);
 524   void gc_epilogue(bool full);
 525 };
 526 
 527 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP