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