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