1 /*
   2  * Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  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).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  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   char* allocate(size_t alignment, size_t* _total_reserved, ReservedSpace* heap_rs);
 137 
 138   // Does operations required after initialization has been done.
 139   void post_initialize();
 140 
 141   // Initialize ("weak") refs processing support
 142   virtual void ref_processing_init();
 143 
 144   virtual CollectedHeap::Name kind() const {
 145     return CollectedHeap::GenCollectedHeap;
 146   }
 147 
 148   Generation* young_gen() { return _young_gen; }
 149   Generation* old_gen()   { return _old_gen; }
 150 
 151   // The generational collector policy.
 152   GenCollectorPolicy* gen_policy() const { return _gen_policy; }
 153 
 154   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) 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 generations level and lower.
 170   void save_used_regions(int level);
 171 
 172   size_t max_capacity() const;
 173 
 174   HeapWord* mem_allocate(size_t size,
 175                          bool*  gc_overhead_limit_was_exceeded);
 176 
 177   // We may support a shared contiguous allocation area, if the youngest
 178   // generation does.
 179   bool supports_inline_contig_alloc() const;
 180   HeapWord** top_addr() const;
 181   HeapWord** end_addr() const;
 182 
 183   // Does this heap support heap inspection? (+PrintClassHistogram)
 184   virtual bool supports_heap_inspection() const { return true; }
 185 
 186   // Perform a full collection of the heap; intended for use in implementing
 187   // "System.gc". This implies as full a collection as the CollectedHeap
 188   // supports. Caller does not hold the Heap_lock on entry.
 189   void collect(GCCause::Cause cause);
 190 
 191   // The same as above but assume that the caller holds the Heap_lock.
 192   void collect_locked(GCCause::Cause cause);
 193 
 194   // Perform a full collection of the first max_level+1 generations.
 195   // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
 196   void collect(GCCause::Cause cause, int max_level);
 197 
 198   // Returns "TRUE" iff "p" points into the committed areas of the heap.
 199   // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
 200   // be expensive to compute in general, so, to prevent
 201   // their inadvertent use in product jvm's, we restrict their use to
 202   // assertion checking or verification only.
 203   bool is_in(const void* p) const;
 204 
 205   // override
 206   bool is_in_closed_subset(const void* p) const {
 207     if (UseConcMarkSweepGC) {
 208       return is_in_reserved(p);
 209     } else {
 210       return is_in(p);
 211     }
 212   }
 213 
 214   // Returns true if the reference is to an object in the reserved space
 215   // for the young generation.
 216   // Assumes the the young gen address range is less than that of the old gen.
 217   bool is_in_young(oop p);
 218 
 219 #ifdef ASSERT
 220   virtual bool is_in_partial_collection(const void* p);
 221 #endif
 222 
 223   virtual bool is_scavengable(const void* addr) {
 224     return is_in_young((oop)addr);
 225   }
 226 
 227   // Iteration functions.
 228   void oop_iterate(ExtendedOopClosure* cl);
 229   void object_iterate(ObjectClosure* cl);
 230   void safe_object_iterate(ObjectClosure* cl);
 231   Space* space_containing(const void* addr) const;
 232 
 233   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
 234   // each address in the (reserved) heap is a member of exactly
 235   // one block.  The defining characteristic of a block is that it is
 236   // possible to find its size, and thus to progress forward to the next
 237   // block.  (Blocks may be of different sizes.)  Thus, blocks may
 238   // represent Java objects, or they might be free blocks in a
 239   // free-list-based heap (or subheap), as long as the two kinds are
 240   // distinguishable and the size of each is determinable.
 241 
 242   // Returns the address of the start of the "block" that contains the
 243   // address "addr".  We say "blocks" instead of "object" since some heaps
 244   // may not pack objects densely; a chunk may either be an object or a
 245   // non-object.
 246   virtual HeapWord* block_start(const void* addr) const;
 247 
 248   // Requires "addr" to be the start of a chunk, and returns its size.
 249   // "addr + size" is required to be the start of a new chunk, or the end
 250   // of the active area of the heap. Assumes (and verifies in non-product
 251   // builds) that addr is in the allocated part of the heap and is
 252   // the start of a chunk.
 253   virtual size_t block_size(const HeapWord* addr) const;
 254 
 255   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 256   // the block is an object. Assumes (and verifies in non-product
 257   // builds) that addr is in the allocated part of the heap and is
 258   // the start of a chunk.
 259   virtual bool block_is_obj(const HeapWord* addr) const;
 260 
 261   // Section on TLAB's.
 262   virtual bool supports_tlab_allocation() const;
 263   virtual size_t tlab_capacity(Thread* thr) const;
 264   virtual size_t tlab_used(Thread* thr) const;
 265   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
 266   virtual HeapWord* allocate_new_tlab(size_t size);
 267 
 268   // Can a compiler initialize a new object without store barriers?
 269   // This permission only extends from the creation of a new object
 270   // via a TLAB up to the first subsequent safepoint.
 271   virtual bool can_elide_tlab_store_barriers() const {
 272     return true;
 273   }
 274 
 275   virtual bool card_mark_must_follow_store() const {
 276     return UseConcMarkSweepGC;
 277   }
 278 
 279   // We don't need barriers for stores to objects in the
 280   // young gen and, a fortiori, for initializing stores to
 281   // objects therein. This applies to DefNew+Tenured and ParNew+CMS
 282   // only and may need to be re-examined in case other
 283   // kinds of collectors are implemented in the future.
 284   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
 285     // We wanted to assert that:-
 286     // assert(UseSerialGC || UseConcMarkSweepGC,
 287     //       "Check can_elide_initializing_store_barrier() for this collector");
 288     // but unfortunately the flag UseSerialGC need not necessarily always
 289     // be set when DefNew+Tenured are being used.
 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   // "level" is the level of the latest collection.
 331   void update_gc_stats(int current_level, bool full) {
 332     _young_gen->update_gc_stats(current_level, full);
 333     _old_gen->update_gc_stats(current_level, full);
 334   }
 335 
 336   // Override.
 337   bool no_gc_in_progress() { return !is_gc_active(); }
 338 
 339   // Override.
 340   void prepare_for_verify();
 341 
 342   // Override.
 343   void verify(bool silent, VerifyOption option);
 344 
 345   // Override.
 346   virtual void print_on(outputStream* st) const;
 347   virtual void print_gc_threads_on(outputStream* st) const;
 348   virtual void gc_threads_do(ThreadClosure* tc) const;
 349   virtual void print_tracing_info() const;
 350   virtual void print_on_error(outputStream* st) const;
 351 
 352   // PrintGC, PrintGCDetails support
 353   void print_heap_change(size_t prev_used) const;
 354 
 355   // The functions below are helper functions that a subclass of
 356   // "CollectedHeap" can use in the implementation of its virtual
 357   // functions.
 358 
 359   class GenClosure : public StackObj {
 360    public:
 361     virtual void do_generation(Generation* gen) = 0;
 362   };
 363 
 364   // Apply "cl.do_generation" to all generations in the heap
 365   // If "old_to_young" determines the order.
 366   void generation_iterate(GenClosure* cl, bool old_to_young);
 367 
 368   void space_iterate(SpaceClosure* cl);
 369 
 370   // Return "true" if all generations have reached the
 371   // maximal committed limit that they can reach, without a garbage
 372   // collection.
 373   virtual bool is_maximal_no_gc() const;
 374 
 375   // Return the generation before "gen".
 376   Generation* prev_gen(Generation* gen) const {
 377     guarantee(gen->level() == 1, "Out of bounds");
 378     return _young_gen;
 379   }
 380 
 381   // Return the generation after "gen".
 382   Generation* next_gen(Generation* gen) const {
 383     guarantee(gen->level() == 0, "Out of bounds");
 384     return _old_gen;
 385   }
 386 
 387   Generation* get_gen(int i) const {
 388     guarantee(i == 0 || i == 1, "Out of bounds");
 389     if (i == 0) {
 390       return _young_gen;
 391     } else {
 392       return _old_gen;
 393     }
 394   }
 395 
 396   int n_gens() const {
 397     assert(_n_gens == gen_policy()->number_of_generations(), "Sanity");
 398     return _n_gens;
 399   }
 400 
 401   // This function returns the "GenRemSet" object that allows us to scan
 402   // generations in a fully generational heap.
 403   GenRemSet* rem_set() { return _rem_set; }
 404 
 405   // Convenience function to be used in situations where the heap type can be
 406   // asserted to be this type.
 407   static GenCollectedHeap* heap();
 408 
 409   void set_par_threads(uint t);
 410 
 411   // Invoke the "do_oop" method of one of the closures "not_older_gens"
 412   // or "older_gens" on root locations for the generation at
 413   // "level".  (The "older_gens" closure is used for scanning references
 414   // from older generations; "not_older_gens" is used everywhere else.)
 415   // If "younger_gens_as_roots" is false, younger generations are
 416   // not scanned as roots; in this case, the caller must be arranging to
 417   // scan the younger generations itself.  (For example, a generation might
 418   // explicitly mark reachable objects in younger generations, to avoid
 419   // excess storage retention.)
 420   // The "so" argument determines which of the roots
 421   // the closure is applied to:
 422   // "SO_None" does none;
 423  private:
 424   void gen_process_roots(int level,
 425                          bool younger_gens_as_roots,
 426                          bool activate_scope,
 427                          SharedHeap::ScanningOption so,
 428                          OopsInGenClosure* not_older_gens,
 429                          OopsInGenClosure* weak_roots,
 430                          OopsInGenClosure* older_gens,
 431                          CLDClosure* cld_closure,
 432                          CLDClosure* weak_cld_closure,
 433                          CodeBlobClosure* code_closure);
 434 
 435  public:
 436   static const bool StrongAndWeakRoots = false;
 437   static const bool StrongRootsOnly    = true;
 438 
 439   void gen_process_roots(int level,
 440                          bool younger_gens_as_roots,
 441                          bool activate_scope,
 442                          SharedHeap::ScanningOption so,
 443                          bool only_strong_roots,
 444                          OopsInGenClosure* not_older_gens,
 445                          OopsInGenClosure* older_gens,
 446                          CLDClosure* cld_closure);
 447 
 448   // Apply "root_closure" to all the weak roots of the system.
 449   // These include JNI weak roots, string table,
 450   // and referents of reachable weak refs.
 451   void gen_process_weak_roots(OopClosure* root_closure);
 452 
 453   // Set the saved marks of generations, if that makes sense.
 454   // In particular, if any generation might iterate over the oops
 455   // in other generations, it should call this method.
 456   void save_marks();
 457 
 458   // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
 459   // allocated since the last call to save_marks in generations at or above
 460   // "level".  The "cur" closure is
 461   // applied to references in the generation at "level", and the "older"
 462   // closure to older generations.
 463 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix)    \
 464   void oop_since_save_marks_iterate(int level,                          \
 465                                     OopClosureType* cur,                \
 466                                     OopClosureType* older);
 467 
 468   ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
 469 
 470 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
 471 
 472   // Returns "true" iff no allocations have occurred in any generation at
 473   // "level" or above since the last
 474   // call to "save_marks".
 475   bool no_allocs_since_save_marks(int level);
 476 
 477   // Returns true if an incremental collection is likely to fail.
 478   // We optionally consult the young gen, if asked to do so;
 479   // otherwise we base our answer on whether the previous incremental
 480   // collection attempt failed with no corrective action as of yet.
 481   bool incremental_collection_will_fail(bool consult_young) {
 482     // Assumes a 2-generation system; the first disjunct remembers if an
 483     // incremental collection failed, even when we thought (second disjunct)
 484     // that it would not.
 485     assert(heap()->collector_policy()->is_generation_policy(),
 486            "the following definition may not be suitable for an n(>2)-generation system");
 487     return incremental_collection_failed() ||
 488            (consult_young && !get_gen(0)->collection_attempt_is_safe());
 489   }
 490 
 491   // If a generation bails out of an incremental collection,
 492   // it sets this flag.
 493   bool incremental_collection_failed() const {
 494     return _incremental_collection_failed;
 495   }
 496   void set_incremental_collection_failed() {
 497     _incremental_collection_failed = true;
 498   }
 499   void clear_incremental_collection_failed() {
 500     _incremental_collection_failed = false;
 501   }
 502 
 503   // Promotion of obj into gen failed.  Try to promote obj to higher
 504   // gens in ascending order; return the new location of obj if successful.
 505   // Otherwise, try expand-and-allocate for obj in both the young and old
 506   // generation; return the new location of obj if successful.  Otherwise, return NULL.
 507   oop handle_failed_promotion(Generation* old_gen,
 508                               oop obj,
 509                               size_t obj_size);
 510 
 511 private:
 512   // Accessor for memory state verification support
 513   NOT_PRODUCT(
 514     static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
 515   )
 516 
 517   // Override
 518   void check_for_non_bad_heap_word_value(HeapWord* addr,
 519     size_t size) PRODUCT_RETURN;
 520 
 521   // For use by mark-sweep.  As implemented, mark-sweep-compact is global
 522   // in an essential way: compaction is performed across generations, by
 523   // iterating over spaces.
 524   void prepare_for_compaction();
 525 
 526   // Perform a full collection of the first max_level+1 generations.
 527   // This is the low level interface used by the public versions of
 528   // collect() and collect_locked(). Caller holds the Heap_lock on entry.
 529   void collect_locked(GCCause::Cause cause, int max_level);
 530 
 531   // Returns success or failure.
 532   bool create_cms_collector();
 533 
 534   // In support of ExplicitGCInvokesConcurrent functionality
 535   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 536   void collect_mostly_concurrent(GCCause::Cause cause);
 537 
 538   // Save the tops of the spaces in all generations
 539   void record_gen_tops_before_GC() PRODUCT_RETURN;
 540 
 541 protected:
 542   virtual void gc_prologue(bool full);
 543   virtual void gc_epilogue(bool full);
 544 };
 545 
 546 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP