1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  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 "memory/collectorPolicy.hpp"
  30 #include "memory/generation.hpp"
  31 #include "memory/sharedHeap.hpp"
  32 
  33 class SubTasksDone;
  34 
  35 // A "GenCollectedHeap" is a SharedHeap that uses generational
  36 // collection.  It is represented with a sequence of Generation's.
  37 class GenCollectedHeap : public SharedHeap {
  38   friend class GenCollectorPolicy;
  39   friend class Generation;
  40   friend class DefNewGeneration;
  41   friend class TenuredGeneration;
  42   friend class ConcurrentMarkSweepGeneration;
  43   friend class CMSCollector;
  44   friend class GenMarkSweep;
  45   friend class VM_GenCollectForAllocation;
  46   friend class VM_GenCollectFull;
  47   friend class VM_GenCollectFullConcurrent;
  48   friend class VM_GC_HeapInspection;
  49   friend class VM_HeapDumper;
  50   friend class HeapInspection;
  51   friend class GCCauseSetter;
  52   friend class VMStructs;
  53 public:
  54   enum SomeConstants {
  55     max_gens = 10
  56   };
  57 
  58   friend class VM_PopulateDumpSharedSpace;
  59 
  60  protected:
  61   // Fields:
  62   static GenCollectedHeap* _gch;
  63 
  64  private:
  65   int _n_gens;
  66   Generation* _gens[max_gens];
  67   GenerationSpec** _gen_specs;
  68 
  69   // The generational collector policy.
  70   GenCollectorPolicy* _gen_policy;
  71 
  72   // Indicates that the most recent previous incremental collection failed.
  73   // The flag is cleared when an action is taken that might clear the
  74   // condition that caused that incremental collection to fail.
  75   bool _incremental_collection_failed;
  76 
  77   // In support of ExplicitGCInvokesConcurrent functionality
  78   unsigned int _full_collections_completed;
  79 
  80   // Data structure for claiming the (potentially) parallel tasks in
  81   // (gen-specific) strong roots processing.
  82   SubTasksDone* _gen_process_strong_tasks;
  83   SubTasksDone* gen_process_strong_tasks() { return _gen_process_strong_tasks; }
  84 
  85   // In block contents verification, the number of header words to skip
  86   NOT_PRODUCT(static size_t _skip_header_HeapWords;)
  87 
  88 protected:
  89   // Directs each generation up to and including "collectedGen" to recompute
  90   // its desired size.
  91   void compute_new_generation_sizes(int collectedGen);
  92 
  93   // Helper functions for allocation
  94   HeapWord* attempt_allocation(size_t size,
  95                                bool   is_tlab,
  96                                bool   first_only);
  97 
  98   // Helper function for two callbacks below.
  99   // Considers collection of the first max_level+1 generations.
 100   void do_collection(bool   full,
 101                      bool   clear_all_soft_refs,
 102                      size_t size,
 103                      bool   is_tlab,
 104                      int    max_level);
 105 
 106   // Callback from VM_GenCollectForAllocation operation.
 107   // This function does everything necessary/possible to satisfy an
 108   // allocation request that failed in the youngest generation that should
 109   // have handled it (including collection, expansion, etc.)
 110   HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
 111 
 112   // Callback from VM_GenCollectFull operation.
 113   // Perform a full collection of the first max_level+1 generations.
 114   virtual void do_full_collection(bool clear_all_soft_refs);
 115   void do_full_collection(bool clear_all_soft_refs, int max_level);
 116 
 117   // Does the "cause" of GC indicate that
 118   // we absolutely __must__ clear soft refs?
 119   bool must_clear_all_soft_refs();
 120 
 121 public:
 122   GenCollectedHeap(GenCollectorPolicy *policy);
 123 
 124   GCStats* gc_stats(int level) const;
 125 
 126   // Returns JNI_OK on success
 127   virtual jint initialize();
 128   char* allocate(size_t alignment,
 129                  size_t* _total_reserved, int* _n_covered_regions,
 130                  ReservedSpace* heap_rs);
 131 
 132   // Does operations required after initialization has been done.
 133   void post_initialize();
 134 
 135   // Initialize ("weak") refs processing support
 136   virtual void ref_processing_init();
 137 
 138   virtual CollectedHeap::Name kind() const {
 139     return CollectedHeap::GenCollectedHeap;
 140   }
 141 
 142   // The generational collector policy.
 143   GenCollectorPolicy* gen_policy() const { return _gen_policy; }
 144   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }
 145 
 146   // Adaptive size policy
 147   virtual AdaptiveSizePolicy* size_policy() {
 148     return gen_policy()->size_policy();
 149   }
 150 
 151   size_t capacity() const;
 152   size_t used() const;
 153 
 154   // Save the "used_region" for generations level and lower.
 155   void save_used_regions(int level);
 156 
 157   size_t max_capacity() const;
 158 
 159   HeapWord* mem_allocate(size_t size,
 160                          bool*  gc_overhead_limit_was_exceeded);
 161 
 162   // We may support a shared contiguous allocation area, if the youngest
 163   // generation does.
 164   bool supports_inline_contig_alloc() const;
 165   HeapWord** top_addr() const;
 166   HeapWord** end_addr() const;
 167 
 168   // Return an estimate of the maximum allocation that could be performed
 169   // without triggering any collection activity.  In a generational
 170   // collector, for example, this is probably the largest allocation that
 171   // could be supported in the youngest generation.  It is "unsafe" because
 172   // no locks are taken; the result should be treated as an approximation,
 173   // not a guarantee.
 174   size_t unsafe_max_alloc();
 175 
 176   // Does this heap support heap inspection? (+PrintClassHistogram)
 177   virtual bool supports_heap_inspection() const { return true; }
 178 
 179   // Perform a full collection of the heap; intended for use in implementing
 180   // "System.gc". This implies as full a collection as the CollectedHeap
 181   // supports. Caller does not hold the Heap_lock on entry.
 182   void collect(GCCause::Cause cause);
 183 
 184   // The same as above but assume that the caller holds the Heap_lock.
 185   void collect_locked(GCCause::Cause cause);
 186 
 187   // Perform a full collection of the first max_level+1 generations.
 188   // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
 189   void collect(GCCause::Cause cause, int max_level);
 190 
 191   // Returns "TRUE" iff "p" points into the committed areas of the heap.
 192   // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
 193   // be expensive to compute in general, so, to prevent
 194   // their inadvertent use in product jvm's, we restrict their use to
 195   // assertion checking or verification only.
 196   bool is_in(const void* p) const;
 197 
 198   // override
 199   bool is_in_closed_subset(const void* p) const {
 200     if (UseConcMarkSweepGC) {
 201       return is_in_reserved(p);
 202     } else {
 203       return is_in(p);
 204     }
 205   }
 206 
 207   // Returns true if the reference is to an object in the reserved space
 208   // for the young generation.
 209   // Assumes the the young gen address range is less than that of the old gen.
 210   bool is_in_young(oop p);
 211 
 212 #ifdef ASSERT
 213   virtual bool is_in_partial_collection(const void* p);
 214 #endif
 215 
 216   virtual bool is_scavengable(const void* addr) {
 217     return is_in_young((oop)addr);
 218   }
 219 
 220   // Iteration functions.
 221   void oop_iterate(ExtendedOopClosure* cl);
 222   void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
 223   void object_iterate(ObjectClosure* cl);
 224   void safe_object_iterate(ObjectClosure* cl);
 225   Space* space_containing(const void* addr) const;
 226 
 227   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
 228   // each address in the (reserved) heap is a member of exactly
 229   // one block.  The defining characteristic of a block is that it is
 230   // possible to find its size, and thus to progress forward to the next
 231   // block.  (Blocks may be of different sizes.)  Thus, blocks may
 232   // represent Java objects, or they might be free blocks in a
 233   // free-list-based heap (or subheap), as long as the two kinds are
 234   // distinguishable and the size of each is determinable.
 235 
 236   // Returns the address of the start of the "block" that contains the
 237   // address "addr".  We say "blocks" instead of "object" since some heaps
 238   // may not pack objects densely; a chunk may either be an object or a
 239   // non-object.
 240   virtual HeapWord* block_start(const void* addr) const;
 241 
 242   // Requires "addr" to be the start of a chunk, and returns its size.
 243   // "addr + size" is required to be the start of a new chunk, or the end
 244   // of the active area of the heap. Assumes (and verifies in non-product
 245   // builds) that addr is in the allocated part of the heap and is
 246   // the start of a chunk.
 247   virtual size_t block_size(const HeapWord* addr) const;
 248 
 249   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 250   // the block is an object. Assumes (and verifies in non-product
 251   // builds) that addr is in the allocated part of the heap and is
 252   // the start of a chunk.
 253   virtual bool block_is_obj(const HeapWord* addr) const;
 254 
 255   // Section on TLAB's.
 256   virtual bool supports_tlab_allocation() const;
 257   virtual size_t tlab_capacity(Thread* thr) const;
 258   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
 259   virtual HeapWord* allocate_new_tlab(size_t size);
 260 
 261   // Can a compiler initialize a new object without store barriers?
 262   // This permission only extends from the creation of a new object
 263   // via a TLAB up to the first subsequent safepoint.
 264   virtual bool can_elide_tlab_store_barriers() const {
 265     return true;
 266   }
 267 
 268   virtual bool card_mark_must_follow_store() const {
 269     return UseConcMarkSweepGC;
 270   }
 271 
 272   // We don't need barriers for stores to objects in the
 273   // young gen and, a fortiori, for initializing stores to
 274   // objects therein. This applies to {DefNew,ParNew}+{Tenured,CMS}
 275   // only and may need to be re-examined in case other
 276   // kinds of collectors are implemented in the future.
 277   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
 278     // We wanted to assert that:-
 279     // assert(UseParNewGC || UseSerialGC || UseConcMarkSweepGC,
 280     //       "Check can_elide_initializing_store_barrier() for this collector");
 281     // but unfortunately the flag UseSerialGC need not necessarily always
 282     // be set when DefNew+Tenured are being used.
 283     return is_in_young(new_obj);
 284   }
 285 
 286   // The "requestor" generation is performing some garbage collection
 287   // action for which it would be useful to have scratch space.  The
 288   // requestor promises to allocate no more than "max_alloc_words" in any
 289   // older generation (via promotion say.)   Any blocks of space that can
 290   // be provided are returned as a list of ScratchBlocks, sorted by
 291   // decreasing size.
 292   ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
 293   // Allow each generation to reset any scratch space that it has
 294   // contributed as it needs.
 295   void release_scratch();
 296 
 297   // Ensure parsability: override
 298   virtual void ensure_parsability(bool retire_tlabs);
 299 
 300   // Time in ms since the longest time a collector ran in
 301   // in any generation.
 302   virtual jlong millis_since_last_gc();
 303 
 304   // Total number of full collections completed.
 305   unsigned int total_full_collections_completed() {
 306     assert(_full_collections_completed <= _total_full_collections,
 307            "Can't complete more collections than were started");
 308     return _full_collections_completed;
 309   }
 310 
 311   // Update above counter, as appropriate, at the end of a stop-world GC cycle
 312   unsigned int update_full_collections_completed();
 313   // Update above counter, as appropriate, at the end of a concurrent GC cycle
 314   unsigned int update_full_collections_completed(unsigned int count);
 315 
 316   // Update "time of last gc" for all constituent generations
 317   // to "now".
 318   void update_time_of_last_gc(jlong now) {
 319     for (int i = 0; i < _n_gens; i++) {
 320       _gens[i]->update_time_of_last_gc(now);
 321     }
 322   }
 323 
 324   // Update the gc statistics for each generation.
 325   // "level" is the level of the lastest collection
 326   void update_gc_stats(int current_level, bool full) {
 327     for (int i = 0; i < _n_gens; i++) {
 328       _gens[i]->update_gc_stats(current_level, full);
 329     }
 330   }
 331 
 332   // Override.
 333   bool no_gc_in_progress() { return !is_gc_active(); }
 334 
 335   // Override.
 336   void prepare_for_verify();
 337 
 338   // Override.
 339   void verify(bool silent, VerifyOption option);
 340 
 341   // Override.
 342   virtual void print_on(outputStream* st) const;
 343   virtual void print_gc_threads_on(outputStream* st) const;
 344   virtual void gc_threads_do(ThreadClosure* tc) const;
 345   virtual void print_tracing_info() const;
 346   virtual void print_on_error(outputStream* st) const;
 347 
 348   // PrintGC, PrintGCDetails support
 349   void print_heap_change(size_t prev_used) const;
 350 
 351   // The functions below are helper functions that a subclass of
 352   // "CollectedHeap" can use in the implementation of its virtual
 353   // functions.
 354 
 355   class GenClosure : public StackObj {
 356    public:
 357     virtual void do_generation(Generation* gen) = 0;
 358   };
 359 
 360   // Apply "cl.do_generation" to all generations in the heap
 361   // If "old_to_young" determines the order.
 362   void generation_iterate(GenClosure* cl, bool old_to_young);
 363 
 364   void space_iterate(SpaceClosure* cl);
 365 
 366   // Return "true" if all generations have reached the
 367   // maximal committed limit that they can reach, without a garbage
 368   // collection.
 369   virtual bool is_maximal_no_gc() const;
 370 
 371   // Return the generation before "gen", or else NULL.
 372   Generation* prev_gen(Generation* gen) const {
 373     int l = gen->level();
 374     if (l == 0) return NULL;
 375     else return _gens[l-1];
 376   }
 377 
 378   // Return the generation after "gen", or else NULL.
 379   Generation* next_gen(Generation* gen) const {
 380     int l = gen->level() + 1;
 381     if (l == _n_gens) return NULL;
 382     else return _gens[l];
 383   }
 384 
 385   Generation* get_gen(int i) const {
 386     if (i >= 0 && i < _n_gens)
 387       return _gens[i];
 388     else
 389       return NULL;
 390   }
 391 
 392   int n_gens() const {
 393     assert(_n_gens == gen_policy()->number_of_generations(), "Sanity");
 394     return _n_gens;
 395   }
 396 
 397   // Convenience function to be used in situations where the heap type can be
 398   // asserted to be this type.
 399   static GenCollectedHeap* heap();
 400 
 401   void set_par_threads(uint t);
 402 
 403   // Invoke the "do_oop" method of one of the closures "not_older_gens"
 404   // or "older_gens" on root locations for the generation at
 405   // "level".  (The "older_gens" closure is used for scanning references
 406   // from older generations; "not_older_gens" is used everywhere else.)
 407   // If "younger_gens_as_roots" is false, younger generations are
 408   // not scanned as roots; in this case, the caller must be arranging to
 409   // scan the younger generations itself.  (For example, a generation might
 410   // explicitly mark reachable objects in younger generations, to avoid
 411   // excess storage retention.)
 412   // The "so" argument determines which of the roots
 413   // the closure is applied to:
 414   // "SO_None" does none;
 415   // "SO_AllClasses" applies the closure to all entries in the SystemDictionary;
 416   // "SO_SystemClasses" to all the "system" classes and loaders;
 417   // "SO_Strings" applies the closure to all entries in the StringTable.
 418   void gen_process_strong_roots(int level,
 419                                 bool younger_gens_as_roots,
 420                                 // The remaining arguments are in an order
 421                                 // consistent with SharedHeap::process_strong_roots:
 422                                 bool activate_scope,
 423                                 bool is_scavenging,
 424                                 SharedHeap::ScanningOption so,
 425                                 OopsInGenClosure* not_older_gens,
 426                                 bool do_code_roots,
 427                                 OopsInGenClosure* older_gens,
 428                                 KlassClosure* klass_closure);
 429 
 430   // Apply "blk" to all the weak roots of the system.  These include
 431   // JNI weak roots, the code cache, system dictionary, symbol table,
 432   // string table, and referents of reachable weak refs.
 433   void gen_process_weak_roots(OopClosure* root_closure,
 434                               CodeBlobClosure* code_roots);
 435 
 436   // Set the saved marks of generations, if that makes sense.
 437   // In particular, if any generation might iterate over the oops
 438   // in other generations, it should call this method.
 439   void save_marks();
 440 
 441   // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
 442   // allocated since the last call to save_marks in generations at or above
 443   // "level".  The "cur" closure is
 444   // applied to references in the generation at "level", and the "older"
 445   // closure to older generations.
 446 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix)    \
 447   void oop_since_save_marks_iterate(int level,                          \
 448                                     OopClosureType* cur,                \
 449                                     OopClosureType* older);
 450 
 451   ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
 452 
 453 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
 454 
 455   // Returns "true" iff no allocations have occurred in any generation at
 456   // "level" or above since the last
 457   // call to "save_marks".
 458   bool no_allocs_since_save_marks(int level);
 459 
 460   // Returns true if an incremental collection is likely to fail.
 461   // We optionally consult the young gen, if asked to do so;
 462   // otherwise we base our answer on whether the previous incremental
 463   // collection attempt failed with no corrective action as of yet.
 464   bool incremental_collection_will_fail(bool consult_young) {
 465     // Assumes a 2-generation system; the first disjunct remembers if an
 466     // incremental collection failed, even when we thought (second disjunct)
 467     // that it would not.
 468     assert(heap()->collector_policy()->is_two_generation_policy(),
 469            "the following definition may not be suitable for an n(>2)-generation system");
 470     return incremental_collection_failed() ||
 471            (consult_young && !get_gen(0)->collection_attempt_is_safe());
 472   }
 473 
 474   // If a generation bails out of an incremental collection,
 475   // it sets this flag.
 476   bool incremental_collection_failed() const {
 477     return _incremental_collection_failed;
 478   }
 479   void set_incremental_collection_failed() {
 480     _incremental_collection_failed = true;
 481   }
 482   void clear_incremental_collection_failed() {
 483     _incremental_collection_failed = false;
 484   }
 485 
 486   // Promotion of obj into gen failed.  Try to promote obj to higher
 487   // gens in ascending order; return the new location of obj if successful.
 488   // Otherwise, try expand-and-allocate for obj in each generation starting at
 489   // gen; return the new location of obj if successful.  Otherwise, return NULL.
 490   oop handle_failed_promotion(Generation* gen,
 491                               oop obj,
 492                               size_t obj_size);
 493 
 494 private:
 495   // Accessor for memory state verification support
 496   NOT_PRODUCT(
 497     static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
 498   )
 499 
 500   // Override
 501   void check_for_non_bad_heap_word_value(HeapWord* addr,
 502     size_t size) PRODUCT_RETURN;
 503 
 504   // For use by mark-sweep.  As implemented, mark-sweep-compact is global
 505   // in an essential way: compaction is performed across generations, by
 506   // iterating over spaces.
 507   void prepare_for_compaction();
 508 
 509   // Perform a full collection of the first max_level+1 generations.
 510   // This is the low level interface used by the public versions of
 511   // collect() and collect_locked(). Caller holds the Heap_lock on entry.
 512   void collect_locked(GCCause::Cause cause, int max_level);
 513 
 514   // Returns success or failure.
 515   bool create_cms_collector();
 516 
 517   // In support of ExplicitGCInvokesConcurrent functionality
 518   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 519   void collect_mostly_concurrent(GCCause::Cause cause);
 520 
 521   // Save the tops of the spaces in all generations
 522   void record_gen_tops_before_GC() PRODUCT_RETURN;
 523 
 524 protected:
 525   virtual void gc_prologue(bool full);
 526   virtual void gc_epilogue(bool full);
 527 };
 528 
 529 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP