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   virtual const char* name() const {
 146     if (UseConcMarkSweepGC) {
 147       return "Concurrent Mark Sweep";
 148     } else {
 149       return "Serial";
 150     }
 151   }
 152 
 153   Generation* young_gen() const { return _young_gen; }
 154   Generation* old_gen()   const { return _old_gen; }
 155 
 156   bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
 157   bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
 158 
 159   // The generational collector policy.
 160   GenCollectorPolicy* gen_policy() const { return _gen_policy; }
 161 
 162   virtual CollectorPolicy* collector_policy() const { return gen_policy(); }
 163 
 164   // Adaptive size policy
 165   virtual AdaptiveSizePolicy* size_policy() {
 166     return gen_policy()->size_policy();
 167   }
 168 
 169   // Return the (conservative) maximum heap alignment
 170   static size_t conservative_max_heap_alignment() {
 171     return Generation::GenGrain;
 172   }
 173 
 174   size_t capacity() const;
 175   size_t used() const;
 176 
 177   // Save the "used_region" for both generations.
 178   void save_used_regions();
 179 
 180   size_t max_capacity() const;
 181 
 182   HeapWord* mem_allocate(size_t size, bool*  gc_overhead_limit_was_exceeded);
 183 
 184   // We may support a shared contiguous allocation area, if the youngest
 185   // generation does.
 186   bool supports_inline_contig_alloc() const;
 187   HeapWord** top_addr() const;
 188   HeapWord** end_addr() const;
 189 
 190   // Perform a full collection of the heap; intended for use in implementing
 191   // "System.gc". This implies as full a collection as the CollectedHeap
 192   // supports. Caller does not hold the Heap_lock on entry.
 193   void collect(GCCause::Cause cause);
 194 
 195   // The same as above but assume that the caller holds the Heap_lock.
 196   void collect_locked(GCCause::Cause cause);
 197 
 198   // Perform a full collection of generations up to and including max_generation.
 199   // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
 200   void collect(GCCause::Cause cause, GenerationType max_generation);
 201 
 202   // Returns "TRUE" iff "p" points into the committed areas of the heap.
 203   // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
 204   // be expensive to compute in general, so, to prevent
 205   // their inadvertent use in product jvm's, we restrict their use to
 206   // assertion checking or verification only.
 207   bool is_in(const void* p) const;
 208 
 209   // override
 210   bool is_in_closed_subset(const void* p) const {
 211     if (UseConcMarkSweepGC) {
 212       return is_in_reserved(p);
 213     } else {
 214       return is_in(p);
 215     }
 216   }
 217 
 218   // Returns true if the reference is to an object in the reserved space
 219   // for the young generation.
 220   // Assumes the the young gen address range is less than that of the old gen.
 221   bool is_in_young(oop p);
 222 
 223 #ifdef ASSERT
 224   bool is_in_partial_collection(const void* p);
 225 #endif
 226 
 227   virtual bool is_scavengable(const void* addr) {
 228     return is_in_young((oop)addr);
 229   }
 230 
 231   // Iteration functions.
 232   void oop_iterate_no_header(OopClosure* cl);
 233   void oop_iterate(ExtendedOopClosure* cl);
 234   void object_iterate(ObjectClosure* cl);
 235   void safe_object_iterate(ObjectClosure* cl);
 236   Space* space_containing(const void* addr) const;
 237 
 238   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
 239   // each address in the (reserved) heap is a member of exactly
 240   // one block.  The defining characteristic of a block is that it is
 241   // possible to find its size, and thus to progress forward to the next
 242   // block.  (Blocks may be of different sizes.)  Thus, blocks may
 243   // represent Java objects, or they might be free blocks in a
 244   // free-list-based heap (or subheap), as long as the two kinds are
 245   // distinguishable and the size of each is determinable.
 246 
 247   // Returns the address of the start of the "block" that contains the
 248   // address "addr".  We say "blocks" instead of "object" since some heaps
 249   // may not pack objects densely; a chunk may either be an object or a
 250   // non-object.
 251   virtual HeapWord* block_start(const void* addr) const;
 252 
 253   // Requires "addr" to be the start of a chunk, and returns its size.
 254   // "addr + size" is required to be the start of a new chunk, or the end
 255   // of the active area of the heap. Assumes (and verifies in non-product
 256   // builds) that addr is in the allocated part of the heap and is
 257   // the start of a chunk.
 258   virtual size_t block_size(const HeapWord* addr) const;
 259 
 260   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 261   // the block is an object. Assumes (and verifies in non-product
 262   // builds) that addr is in the allocated part of the heap and is
 263   // the start of a chunk.
 264   virtual bool block_is_obj(const HeapWord* addr) const;
 265 
 266   // Section on TLAB's.
 267   virtual bool supports_tlab_allocation() const;
 268   virtual size_t tlab_capacity(Thread* thr) const;
 269   virtual size_t tlab_used(Thread* thr) const;
 270   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
 271   virtual HeapWord* allocate_new_tlab(size_t size);
 272 
 273   // Can a compiler initialize a new object without store barriers?
 274   // This permission only extends from the creation of a new object
 275   // via a TLAB up to the first subsequent safepoint.
 276   virtual bool can_elide_tlab_store_barriers() const {
 277     return true;
 278   }
 279 
 280   virtual bool card_mark_must_follow_store() const {
 281     return UseConcMarkSweepGC;
 282   }
 283 
 284   // We don't need barriers for stores to objects in the
 285   // young gen and, a fortiori, for initializing stores to
 286   // objects therein. This applies to DefNew+Tenured and ParNew+CMS
 287   // only and may need to be re-examined in case other
 288   // kinds of collectors are implemented in the future.
 289   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
 290     return is_in_young(new_obj);
 291   }
 292 
 293   // The "requestor" generation is performing some garbage collection
 294   // action for which it would be useful to have scratch space.  The
 295   // requestor promises to allocate no more than "max_alloc_words" in any
 296   // older generation (via promotion say.)   Any blocks of space that can
 297   // be provided are returned as a list of ScratchBlocks, sorted by
 298   // decreasing size.
 299   ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
 300   // Allow each generation to reset any scratch space that it has
 301   // contributed as it needs.
 302   void release_scratch();
 303 
 304   // Ensure parsability: override
 305   virtual void ensure_parsability(bool retire_tlabs);
 306 
 307   // Time in ms since the longest time a collector ran in
 308   // in any generation.
 309   virtual jlong millis_since_last_gc();
 310 
 311   // Total number of full collections completed.
 312   unsigned int total_full_collections_completed() {
 313     assert(_full_collections_completed <= _total_full_collections,
 314            "Can't complete more collections than were started");
 315     return _full_collections_completed;
 316   }
 317 
 318   // Update above counter, as appropriate, at the end of a stop-world GC cycle
 319   unsigned int update_full_collections_completed();
 320   // Update above counter, as appropriate, at the end of a concurrent GC cycle
 321   unsigned int update_full_collections_completed(unsigned int count);
 322 
 323   // Update "time of last gc" for all generations to "now".
 324   void update_time_of_last_gc(jlong now) {
 325     _young_gen->update_time_of_last_gc(now);
 326     _old_gen->update_time_of_last_gc(now);
 327   }
 328 
 329   // Update the gc statistics for each generation.
 330   void update_gc_stats(Generation* current_generation, bool full) {
 331     _old_gen->update_gc_stats(current_generation, 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(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   void print_heap_change(size_t young_prev_used, size_t old_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   // Return "true" if all generations have reached the
 365   // maximal committed limit that they can reach, without a garbage
 366   // collection.
 367   virtual bool is_maximal_no_gc() const;
 368 
 369   // This function returns the CardTableRS object that allows us to scan
 370   // generations in a fully generational heap.
 371   CardTableRS* rem_set() { return _rem_set; }
 372 
 373   // Convenience function to be used in situations where the heap type can be
 374   // asserted to be this type.
 375   static GenCollectedHeap* heap();
 376 
 377   // The ScanningOption determines which of the roots
 378   // the closure is applied to:
 379   // "SO_None" does none;
 380   enum ScanningOption {
 381     SO_None                =  0x0,
 382     SO_AllCodeCache        =  0x8,
 383     SO_ScavengeCodeCache   = 0x10
 384   };
 385 
 386  private:
 387   void process_roots(StrongRootsScope* scope,
 388                      ScanningOption so,
 389                      OopClosure* strong_roots,
 390                      OopClosure* weak_roots,
 391                      CLDClosure* strong_cld_closure,
 392                      CLDClosure* weak_cld_closure,
 393                      CodeBlobToOopClosure* code_roots);
 394 
 395  public:
 396   void young_process_roots(StrongRootsScope* scope,
 397                            OopsInGenClosure* root_closure,
 398                            OopsInGenClosure* old_gen_closure,
 399                            CLDClosure* cld_closure);
 400 
 401   // If "young_gen_as_roots" is false, younger generations are
 402   // not scanned as roots; in this case, the caller must be arranging to
 403   // scan the younger generations itself.  (For example, a generation might
 404   // explicitly mark reachable objects in younger generations, to avoid
 405   // excess storage retention.)
 406   void cms_process_roots(StrongRootsScope* scope,
 407                          bool young_gen_as_roots,
 408                          ScanningOption so,
 409                          bool only_strong_roots,
 410                          OopsInGenClosure* root_closure,
 411                          CLDClosure* cld_closure);
 412 
 413   void full_process_roots(StrongRootsScope* scope,
 414                           bool only_strong_roots,
 415                           ScanningOption so,
 416                           bool is_adjust_phase,
 417                           OopsInGenClosure* root_closure,
 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(GenerationType start_gen,           \
 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 since the last
 445   // call to "save_marks".
 446   bool no_allocs_since_save_marks();
 447 
 448   // Returns true if an incremental collection is likely to fail.
 449   // We optionally consult the young gen, if asked to do so;
 450   // otherwise we base our answer on whether the previous incremental
 451   // collection attempt failed with no corrective action as of yet.
 452   bool incremental_collection_will_fail(bool consult_young) {
 453     // The first disjunct remembers if an incremental collection failed, even
 454     // when we thought (second disjunct) that it would not.
 455     return incremental_collection_failed() ||
 456            (consult_young && !_young_gen->collection_attempt_is_safe());
 457   }
 458 
 459   // If a generation bails out of an incremental collection,
 460   // it sets this flag.
 461   bool incremental_collection_failed() const {
 462     return _incremental_collection_failed;
 463   }
 464   void set_incremental_collection_failed() {
 465     _incremental_collection_failed = true;
 466   }
 467   void clear_incremental_collection_failed() {
 468     _incremental_collection_failed = false;
 469   }
 470 
 471   // Promotion of obj into gen failed.  Try to promote obj to higher
 472   // gens in ascending order; return the new location of obj if successful.
 473   // Otherwise, try expand-and-allocate for obj in both the young and old
 474   // generation; return the new location of obj if successful.  Otherwise, return NULL.
 475   oop handle_failed_promotion(Generation* old_gen,
 476                               oop obj,
 477                               size_t obj_size);
 478 
 479 private:
 480   // Accessor for memory state verification support
 481   NOT_PRODUCT(
 482     static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
 483   )
 484 
 485   // Override
 486   void check_for_non_bad_heap_word_value(HeapWord* addr,
 487     size_t size) PRODUCT_RETURN;
 488 
 489   // For use by mark-sweep.  As implemented, mark-sweep-compact is global
 490   // in an essential way: compaction is performed across generations, by
 491   // iterating over spaces.
 492   void prepare_for_compaction();
 493 
 494   // Perform a full collection of the generations up to and including max_generation.
 495   // This is the low level interface used by the public versions of
 496   // collect() and collect_locked(). Caller holds the Heap_lock on entry.
 497   void collect_locked(GCCause::Cause cause, GenerationType max_generation);
 498 
 499   // Returns success or failure.
 500   bool create_cms_collector();
 501 
 502   // In support of ExplicitGCInvokesConcurrent functionality
 503   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 504   void collect_mostly_concurrent(GCCause::Cause cause);
 505 
 506   // Save the tops of the spaces in all generations
 507   void record_gen_tops_before_GC() PRODUCT_RETURN;
 508 
 509 protected:
 510   void gc_prologue(bool full);
 511   void gc_epilogue(bool full);
 512 
 513 public:
 514   void stop();
 515 };
 516 
 517 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP