1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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 has two generations, young and old.
  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 
  67   Generation* _young_gen;
  68   Generation* _old_gen;
  69 
  70   // The singleton Gen Remembered Set.
  71   GenRemSet* _rem_set;
  72 
  73   // The generational collector policy.
  74   GenCollectorPolicy* _gen_policy;
  75 
  76   // Indicates that the most recent previous incremental collection failed.
  77   // The flag is cleared when an action is taken that might clear the
  78   // condition that caused that incremental collection to fail.
  79   bool _incremental_collection_failed;
  80 
  81   // In support of ExplicitGCInvokesConcurrent functionality
  82   unsigned int _full_collections_completed;
  83 
  84   // Data structure for claiming the (potentially) parallel tasks in
  85   // (gen-specific) roots processing.
  86   SubTasksDone* _process_strong_tasks;
  87 
  88   // Collects the given generation.
  89   void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
  90                           bool run_verification, bool clear_soft_refs,
  91                           bool restore_marks_for_biased_locking);
  92 
  93   // In block contents verification, the number of header words to skip
  94   NOT_PRODUCT(static size_t _skip_header_HeapWords;)
  95 
  96 protected:
  97   // Helper functions for allocation
  98   HeapWord* attempt_allocation(size_t size,
  99                                bool   is_tlab,
 100                                bool   first_only);
 101 
 102   // Helper function for two callbacks below.
 103   // Considers collection of the first max_level+1 generations.
 104   void do_collection(bool   full,
 105                      bool   clear_all_soft_refs,
 106                      size_t size,
 107                      bool   is_tlab,
 108                      int    max_level);
 109 
 110   // Callback from VM_GenCollectForAllocation operation.
 111   // This function does everything necessary/possible to satisfy an
 112   // allocation request that failed in the youngest generation that should
 113   // have handled it (including collection, expansion, etc.)
 114   HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
 115 
 116   // Callback from VM_GenCollectFull operation.
 117   // Perform a full collection of the first max_level+1 generations.
 118   virtual void do_full_collection(bool clear_all_soft_refs);
 119   void do_full_collection(bool clear_all_soft_refs, int max_level);
 120 
 121   // Does the "cause" of GC indicate that
 122   // we absolutely __must__ clear soft refs?
 123   bool must_clear_all_soft_refs();
 124 
 125 public:
 126   GenCollectedHeap(GenCollectorPolicy *policy);
 127 
 128   GCStats* gc_stats(int level) const;
 129 
 130   // Returns JNI_OK on success
 131   virtual jint initialize();
 132 
 133   // Reserve aligned space for the heap as needed by the contained generations.
 134   char* allocate(size_t alignment, ReservedSpace* heap_rs);
 135 
 136   // Does operations required after initialization has been done.
 137   void post_initialize();
 138 
 139   // Initialize ("weak") refs processing support
 140   virtual void ref_processing_init();
 141 
 142   virtual Name kind() const {
 143     return CollectedHeap::GenCollectedHeap;
 144   }
 145 
 146   Generation* young_gen() const { return _young_gen; }
 147   Generation* old_gen()   const { return _old_gen; }
 148 
 149   // The generational collector policy.
 150   GenCollectorPolicy* gen_policy() const { return _gen_policy; }
 151 
 152   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }
 153 
 154   // Adaptive size policy
 155   virtual AdaptiveSizePolicy* size_policy() {
 156     return gen_policy()->size_policy();
 157   }
 158 
 159   // Return the (conservative) maximum heap alignment
 160   static size_t conservative_max_heap_alignment() {
 161     return Generation::GenGrain;
 162   }
 163 
 164   size_t capacity() const;
 165   size_t used() const;
 166 
 167   // Save the "used_region" for generations level and lower.
 168   void save_used_regions(int level);
 169 
 170   size_t max_capacity() const;
 171 
 172   HeapWord* mem_allocate(size_t size,
 173                          bool*  gc_overhead_limit_was_exceeded);
 174 
 175   // We may support a shared contiguous allocation area, if the youngest
 176   // generation does.
 177   bool supports_inline_contig_alloc() const;
 178   HeapWord** top_addr() const;
 179   HeapWord** end_addr() const;
 180 
 181   // Does this heap support heap inspection? (+PrintClassHistogram)
 182   virtual bool supports_heap_inspection() const { return true; }
 183 
 184   // Perform a full collection of the heap; intended for use in implementing
 185   // "System.gc". This implies as full a collection as the CollectedHeap
 186   // supports. Caller does not hold the Heap_lock on entry.
 187   void collect(GCCause::Cause cause);
 188 
 189   // The same as above but assume that the caller holds the Heap_lock.
 190   void collect_locked(GCCause::Cause cause);
 191 
 192   // Perform a full collection of the first max_level+1 generations.
 193   // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
 194   void collect(GCCause::Cause cause, int max_level);
 195 
 196   // Returns "TRUE" iff "p" points into the committed areas of the heap.
 197   // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
 198   // be expensive to compute in general, so, to prevent
 199   // their inadvertent use in product jvm's, we restrict their use to
 200   // assertion checking or verification only.
 201   bool is_in(const void* p) const;
 202 
 203   // override
 204   bool is_in_closed_subset(const void* p) const {
 205     if (UseConcMarkSweepGC) {
 206       return is_in_reserved(p);
 207     } else {
 208       return is_in(p);
 209     }
 210   }
 211 
 212   // Returns true if the reference is to an object in the reserved space
 213   // for the young generation.
 214   // Assumes the the young gen address range is less than that of the old gen.
 215   bool is_in_young(oop p);
 216 
 217 #ifdef ASSERT
 218   bool is_in_partial_collection(const void* p);
 219 #endif
 220 
 221   virtual bool is_scavengable(const void* addr) {
 222     return is_in_young((oop)addr);
 223   }
 224 
 225   // Iteration functions.
 226   void oop_iterate(ExtendedOopClosure* cl);
 227   void object_iterate(ObjectClosure* cl);
 228   void safe_object_iterate(ObjectClosure* cl);
 229   Space* space_containing(const void* addr) const;
 230 
 231   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
 232   // each address in the (reserved) heap is a member of exactly
 233   // one block.  The defining characteristic of a block is that it is
 234   // possible to find its size, and thus to progress forward to the next
 235   // block.  (Blocks may be of different sizes.)  Thus, blocks may
 236   // represent Java objects, or they might be free blocks in a
 237   // free-list-based heap (or subheap), as long as the two kinds are
 238   // distinguishable and the size of each is determinable.
 239 
 240   // Returns the address of the start of the "block" that contains the
 241   // address "addr".  We say "blocks" instead of "object" since some heaps
 242   // may not pack objects densely; a chunk may either be an object or a
 243   // non-object.
 244   virtual HeapWord* block_start(const void* addr) const;
 245 
 246   // Requires "addr" to be the start of a chunk, and returns its size.
 247   // "addr + size" is required to be the start of a new chunk, or the end
 248   // of the active area of the heap. Assumes (and verifies in non-product
 249   // builds) that addr is in the allocated part of the heap and is
 250   // the start of a chunk.
 251   virtual size_t block_size(const HeapWord* addr) const;
 252 
 253   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 254   // the block is an object. Assumes (and verifies in non-product
 255   // builds) that addr is in the allocated part of the heap and is
 256   // the start of a chunk.
 257   virtual bool block_is_obj(const HeapWord* addr) const;
 258 
 259   // Section on TLAB's.
 260   virtual bool supports_tlab_allocation() const;
 261   virtual size_t tlab_capacity(Thread* thr) const;
 262   virtual size_t tlab_used(Thread* thr) const;
 263   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
 264   virtual HeapWord* allocate_new_tlab(size_t size);
 265 
 266   // Can a compiler initialize a new object without store barriers?
 267   // This permission only extends from the creation of a new object
 268   // via a TLAB up to the first subsequent safepoint.
 269   virtual bool can_elide_tlab_store_barriers() const {
 270     return true;
 271   }
 272 
 273   virtual bool card_mark_must_follow_store() const {
 274     return UseConcMarkSweepGC;
 275   }
 276 
 277   // We don't need barriers for stores to objects in the
 278   // young gen and, a fortiori, for initializing stores to
 279   // objects therein. This applies to DefNew+Tenured and ParNew+CMS
 280   // only and may need to be re-examined in case other
 281   // kinds of collectors are implemented in the future.
 282   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
 283     // We wanted to assert that:-
 284     // assert(UseSerialGC || UseConcMarkSweepGC,
 285     //       "Check can_elide_initializing_store_barrier() for this collector");
 286     // but unfortunately the flag UseSerialGC need not necessarily always
 287     // be set when DefNew+Tenured are being used.
 288     return is_in_young(new_obj);
 289   }
 290 
 291   // The "requestor" generation is performing some garbage collection
 292   // action for which it would be useful to have scratch space.  The
 293   // requestor promises to allocate no more than "max_alloc_words" in any
 294   // older generation (via promotion say.)   Any blocks of space that can
 295   // be provided are returned as a list of ScratchBlocks, sorted by
 296   // decreasing size.
 297   ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
 298   // Allow each generation to reset any scratch space that it has
 299   // contributed as it needs.
 300   void release_scratch();
 301 
 302   // Ensure parsability: override
 303   virtual void ensure_parsability(bool retire_tlabs);
 304 
 305   // Time in ms since the longest time a collector ran in
 306   // in any generation.
 307   virtual jlong millis_since_last_gc();
 308 
 309   // Total number of full collections completed.
 310   unsigned int total_full_collections_completed() {
 311     assert(_full_collections_completed <= _total_full_collections,
 312            "Can't complete more collections than were started");
 313     return _full_collections_completed;
 314   }
 315 
 316   // Update above counter, as appropriate, at the end of a stop-world GC cycle
 317   unsigned int update_full_collections_completed();
 318   // Update above counter, as appropriate, at the end of a concurrent GC cycle
 319   unsigned int update_full_collections_completed(unsigned int count);
 320 
 321   // Update "time of last gc" for all generations to "now".
 322   void update_time_of_last_gc(jlong now) {
 323     _young_gen->update_time_of_last_gc(now);
 324     _old_gen->update_time_of_last_gc(now);
 325   }
 326 
 327   // Update the gc statistics for each generation.
 328   // "level" is the level of the latest collection.
 329   void update_gc_stats(int current_level, bool full) {
 330     _young_gen->update_gc_stats(current_level, full);
 331     _old_gen->update_gc_stats(current_level, full);
 332   }
 333 
 334   bool no_gc_in_progress() { return !is_gc_active(); }
 335 
 336   // Override.
 337   void prepare_for_verify();
 338 
 339   // Override.
 340   void verify(bool silent, VerifyOption option);
 341 
 342   // Override.
 343   virtual void print_on(outputStream* st) const;
 344   virtual void print_gc_threads_on(outputStream* st) const;
 345   virtual void gc_threads_do(ThreadClosure* tc) const;
 346   virtual void print_tracing_info() const;
 347   virtual void print_on_error(outputStream* st) const;
 348 
 349   // PrintGC, PrintGCDetails support
 350   void print_heap_change(size_t 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   int n_gens() const {
 371     assert(_n_gens == gen_policy()->number_of_generations(), "Sanity");
 372     return _n_gens;
 373   }
 374 
 375   // This function returns the "GenRemSet" object that allows us to scan
 376   // generations in a fully generational heap.
 377   GenRemSet* rem_set() { return _rem_set; }
 378 
 379   // Convenience function to be used in situations where the heap type can be
 380   // asserted to be this type.
 381   static GenCollectedHeap* heap();
 382 
 383   void set_par_threads(uint t);
 384   void set_n_termination(uint t);
 385 
 386   // Invoke the "do_oop" method of one of the closures "not_older_gens"
 387   // or "older_gens" on root locations for the generation at
 388   // "level".  (The "older_gens" closure is used for scanning references
 389   // from older generations; "not_older_gens" is used everywhere else.)
 390   // If "younger_gens_as_roots" is false, younger generations are
 391   // not scanned as roots; in this case, the caller must be arranging to
 392   // scan the younger generations itself.  (For example, a generation might
 393   // explicitly mark reachable objects in younger generations, to avoid
 394   // excess storage retention.)
 395   // The "so" argument determines which of the roots
 396   // the closure is applied to:
 397   // "SO_None" does none;
 398   enum ScanningOption {
 399     SO_None                =  0x0,
 400     SO_AllCodeCache        =  0x8,
 401     SO_ScavengeCodeCache   = 0x10
 402   };
 403 
 404  private:
 405   void process_roots(bool activate_scope,
 406                      ScanningOption so,
 407                      OopClosure* strong_roots,
 408                      OopClosure* weak_roots,
 409                      CLDClosure* strong_cld_closure,
 410                      CLDClosure* weak_cld_closure,
 411                      CodeBlobClosure* code_roots);
 412 
 413   void gen_process_roots(int level,
 414                          bool younger_gens_as_roots,
 415                          bool activate_scope,
 416                          ScanningOption so,
 417                          OopsInGenClosure* not_older_gens,
 418                          OopsInGenClosure* weak_roots,
 419                          OopsInGenClosure* older_gens,
 420                          CLDClosure* cld_closure,
 421                          CLDClosure* weak_cld_closure,
 422                          CodeBlobClosure* code_closure);
 423 
 424  public:
 425   static const bool StrongAndWeakRoots = false;
 426   static const bool StrongRootsOnly    = true;
 427 
 428   void gen_process_roots(int level,
 429                          bool younger_gens_as_roots,
 430                          bool activate_scope,
 431                          ScanningOption so,
 432                          bool only_strong_roots,
 433                          OopsInGenClosure* not_older_gens,
 434                          OopsInGenClosure* older_gens,
 435                          CLDClosure* cld_closure);
 436 
 437   // Apply "root_closure" to all the weak roots of the system.
 438   // These include JNI weak roots, string table,
 439   // and referents of reachable weak refs.
 440   void gen_process_weak_roots(OopClosure* root_closure);
 441 
 442   // Set the saved marks of generations, if that makes sense.
 443   // In particular, if any generation might iterate over the oops
 444   // in other generations, it should call this method.
 445   void save_marks();
 446 
 447   // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
 448   // allocated since the last call to save_marks in generations at or above
 449   // "level".  The "cur" closure is
 450   // applied to references in the generation at "level", and the "older"
 451   // closure to older generations.
 452 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix)    \
 453   void oop_since_save_marks_iterate(int level,                          \
 454                                     OopClosureType* cur,                \
 455                                     OopClosureType* older);
 456 
 457   ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
 458 
 459 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
 460 
 461   // Returns "true" iff no allocations have occurred in any generation at
 462   // "level" or above since the last
 463   // call to "save_marks".
 464   bool no_allocs_since_save_marks(int level);
 465 
 466   // Returns true if an incremental collection is likely to fail.
 467   // We optionally consult the young gen, if asked to do so;
 468   // otherwise we base our answer on whether the previous incremental
 469   // collection attempt failed with no corrective action as of yet.
 470   bool incremental_collection_will_fail(bool consult_young) {
 471     // Assumes a 2-generation system; the first disjunct remembers if an
 472     // incremental collection failed, even when we thought (second disjunct)
 473     // that it would not.
 474     assert(heap()->collector_policy()->is_generation_policy(),
 475            "the following definition may not be suitable for an n(>2)-generation system");
 476     return incremental_collection_failed() ||
 477            (consult_young && !_young_gen->collection_attempt_is_safe());
 478   }
 479 
 480   // If a generation bails out of an incremental collection,
 481   // it sets this flag.
 482   bool incremental_collection_failed() const {
 483     return _incremental_collection_failed;
 484   }
 485   void set_incremental_collection_failed() {
 486     _incremental_collection_failed = true;
 487   }
 488   void clear_incremental_collection_failed() {
 489     _incremental_collection_failed = false;
 490   }
 491 
 492   // Promotion of obj into gen failed.  Try to promote obj to higher
 493   // gens in ascending order; return the new location of obj if successful.
 494   // Otherwise, try expand-and-allocate for obj in both the young and old
 495   // generation; return the new location of obj if successful.  Otherwise, return NULL.
 496   oop handle_failed_promotion(Generation* old_gen,
 497                               oop obj,
 498                               size_t obj_size);
 499 
 500 private:
 501   // Accessor for memory state verification support
 502   NOT_PRODUCT(
 503     static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
 504   )
 505 
 506   // Override
 507   void check_for_non_bad_heap_word_value(HeapWord* addr,
 508     size_t size) PRODUCT_RETURN;
 509 
 510   // For use by mark-sweep.  As implemented, mark-sweep-compact is global
 511   // in an essential way: compaction is performed across generations, by
 512   // iterating over spaces.
 513   void prepare_for_compaction();
 514 
 515   // Perform a full collection of the first max_level+1 generations.
 516   // This is the low level interface used by the public versions of
 517   // collect() and collect_locked(). Caller holds the Heap_lock on entry.
 518   void collect_locked(GCCause::Cause cause, int max_level);
 519 
 520   // Returns success or failure.
 521   bool create_cms_collector();
 522 
 523   // In support of ExplicitGCInvokesConcurrent functionality
 524   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 525   void collect_mostly_concurrent(GCCause::Cause cause);
 526 
 527   // Save the tops of the spaces in all generations
 528   void record_gen_tops_before_GC() PRODUCT_RETURN;
 529 
 530 protected:
 531   void gc_prologue(bool full);
 532   void gc_epilogue(bool full);
 533 };
 534 
 535 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP