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