1 /*
   2  * Copyright (c) 2000, 2014, 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 is represented with a sequence of Generation's.
  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   Generation* _gens[max_gens];
  67   GenerationSpec** _gen_specs;
  68 
  69   // The singleton Gen Remembered Set.
  70   GenRemSet* _rem_set;
  71 
  72   // The generational collector policy.
  73   GenCollectorPolicy* _gen_policy;
  74 
  75   // Indicates that the most recent previous incremental collection failed.
  76   // The flag is cleared when an action is taken that might clear the
  77   // condition that caused that incremental collection to fail.
  78   bool _incremental_collection_failed;
  79 
  80   // In support of ExplicitGCInvokesConcurrent functionality
  81   unsigned int _full_collections_completed;
  82 
  83   // Data structure for claiming the (potentially) parallel tasks in
  84   // (gen-specific) roots processing.
  85   SubTasksDone* _gen_process_roots_tasks;
  86   SubTasksDone* gen_process_roots_tasks() { return _gen_process_roots_tasks; }
  87 
  88   // In block contents verification, the number of header words to skip
  89   NOT_PRODUCT(static size_t _skip_header_HeapWords;)
  90 
  91 protected:
  92   // Helper functions for allocation
  93   HeapWord* attempt_allocation(size_t size,
  94                                bool   is_tlab,
  95                                bool   first_only);
  96 
  97   // Helper function for two callbacks below.
  98   // Considers collection of the first max_level+1 generations.
  99   void do_collection(bool   full,
 100                      bool   clear_all_soft_refs,
 101                      size_t size,
 102                      bool   is_tlab,
 103                      int    max_level);
 104 
 105   // Callback from VM_GenCollectForAllocation operation.
 106   // This function does everything necessary/possible to satisfy an
 107   // allocation request that failed in the youngest generation that should
 108   // have handled it (including collection, expansion, etc.)
 109   HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
 110 
 111   // Callback from VM_GenCollectFull operation.
 112   // Perform a full collection of the first max_level+1 generations.
 113   virtual void do_full_collection(bool clear_all_soft_refs);
 114   void do_full_collection(bool clear_all_soft_refs, int max_level);
 115 
 116   // Does the "cause" of GC indicate that
 117   // we absolutely __must__ clear soft refs?
 118   bool must_clear_all_soft_refs();
 119 
 120 public:
 121   GenCollectedHeap(GenCollectorPolicy *policy);
 122 
 123   GCStats* gc_stats(int level) const;
 124 
 125   // Returns JNI_OK on success
 126   virtual jint initialize();
 127   char* allocate(size_t alignment, size_t* _total_reserved, ReservedSpace* heap_rs);
 128 
 129   // Does operations required after initialization has been done.
 130   void post_initialize();
 131 
 132   // Initialize ("weak") refs processing support
 133   virtual void ref_processing_init();
 134 
 135   virtual CollectedHeap::Name kind() const {
 136     return CollectedHeap::GenCollectedHeap;
 137   }
 138 
 139   // The generational collector policy.
 140   GenCollectorPolicy* gen_policy() const { return _gen_policy; }
 141   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }
 142 
 143   // Adaptive size policy
 144   virtual AdaptiveSizePolicy* size_policy() {
 145     return gen_policy()->size_policy();
 146   }
 147 
 148   // Return the (conservative) maximum heap alignment
 149   static size_t conservative_max_heap_alignment() {
 150     return Generation::GenGrain;
 151   }
 152 
 153   size_t capacity() const;
 154   size_t used() const;
 155 
 156   // Save the "used_region" for generations level and lower.
 157   void save_used_regions(int level);
 158 
 159   size_t max_capacity() const;
 160 
 161   HeapWord* mem_allocate(size_t size,
 162                          bool*  gc_overhead_limit_was_exceeded);
 163 
 164   // We may support a shared contiguous allocation area, if the youngest
 165   // generation does.
 166   bool supports_inline_contig_alloc() const;
 167   HeapWord** top_addr() const;
 168   HeapWord** end_addr() const;
 169 
 170   // Does this heap support heap inspection? (+PrintClassHistogram)
 171   virtual bool supports_heap_inspection() const { return true; }
 172 
 173   // Perform a full collection of the heap; intended for use in implementing
 174   // "System.gc". This implies as full a collection as the CollectedHeap
 175   // supports. Caller does not hold the Heap_lock on entry.
 176   void collect(GCCause::Cause cause);
 177 
 178   // The same as above but assume that the caller holds the Heap_lock.
 179   void collect_locked(GCCause::Cause cause);
 180 
 181   // Perform a full collection of the first max_level+1 generations.
 182   // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
 183   void collect(GCCause::Cause cause, int max_level);
 184 
 185   // Returns "TRUE" iff "p" points into the committed areas of the heap.
 186   // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
 187   // be expensive to compute in general, so, to prevent
 188   // their inadvertent use in product jvm's, we restrict their use to
 189   // assertion checking or verification only.
 190   bool is_in(const void* p) const;
 191 
 192   // override
 193   bool is_in_closed_subset(const void* p) const {
 194     if (UseConcMarkSweepGC) {
 195       return is_in_reserved(p);
 196     } else {
 197       return is_in(p);
 198     }
 199   }
 200 
 201   // Returns true if the reference is to an object in the reserved space
 202   // for the young generation.
 203   // Assumes the the young gen address range is less than that of the old gen.
 204   bool is_in_young(oop p);
 205 
 206 #ifdef ASSERT
 207   virtual bool is_in_partial_collection(const void* p);
 208 #endif
 209 
 210   virtual bool is_scavengable(const void* addr) {
 211     return is_in_young((oop)addr);
 212   }
 213 
 214   // Iteration functions.
 215   void oop_iterate(ExtendedOopClosure* cl);
 216   void object_iterate(ObjectClosure* cl);
 217   void safe_object_iterate(ObjectClosure* cl);
 218   Space* space_containing(const void* addr) const;
 219 
 220   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
 221   // each address in the (reserved) heap is a member of exactly
 222   // one block.  The defining characteristic of a block is that it is
 223   // possible to find its size, and thus to progress forward to the next
 224   // block.  (Blocks may be of different sizes.)  Thus, blocks may
 225   // represent Java objects, or they might be free blocks in a
 226   // free-list-based heap (or subheap), as long as the two kinds are
 227   // distinguishable and the size of each is determinable.
 228 
 229   // Returns the address of the start of the "block" that contains the
 230   // address "addr".  We say "blocks" instead of "object" since some heaps
 231   // may not pack objects densely; a chunk may either be an object or a
 232   // non-object.
 233   virtual HeapWord* block_start(const void* addr) const;
 234 
 235   // Requires "addr" to be the start of a chunk, and returns its size.
 236   // "addr + size" is required to be the start of a new chunk, or the end
 237   // of the active area of the heap. Assumes (and verifies in non-product
 238   // builds) that addr is in the allocated part of the heap and is
 239   // the start of a chunk.
 240   virtual size_t block_size(const HeapWord* addr) const;
 241 
 242   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 243   // the block is an object. Assumes (and verifies in non-product
 244   // builds) that addr is in the allocated part of the heap and is
 245   // the start of a chunk.
 246   virtual bool block_is_obj(const HeapWord* addr) const;
 247 
 248   // Section on TLAB's.
 249   virtual bool supports_tlab_allocation() const;
 250   virtual size_t tlab_capacity(Thread* thr) const;
 251   virtual size_t tlab_used(Thread* thr) const;
 252   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
 253   virtual HeapWord* allocate_new_tlab(size_t size);
 254 
 255   // Can a compiler initialize a new object without store barriers?
 256   // This permission only extends from the creation of a new object
 257   // via a TLAB up to the first subsequent safepoint.
 258   virtual bool can_elide_tlab_store_barriers() const {
 259     return true;
 260   }
 261 
 262   virtual bool card_mark_must_follow_store() const {
 263     return UseConcMarkSweepGC;
 264   }
 265 
 266   // We don't need barriers for stores to objects in the
 267   // young gen and, a fortiori, for initializing stores to
 268   // objects therein. This applies to DefNew+Tenured and ParNew+CMS
 269   // only and may need to be re-examined in case other
 270   // kinds of collectors are implemented in the future.
 271   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
 272     // We wanted to assert that:-
 273     // assert(UseSerialGC || UseConcMarkSweepGC,
 274     //       "Check can_elide_initializing_store_barrier() for this collector");
 275     // but unfortunately the flag UseSerialGC need not necessarily always
 276     // be set when DefNew+Tenured are being used.
 277     return is_in_young(new_obj);
 278   }
 279 
 280   // The "requestor" generation is performing some garbage collection
 281   // action for which it would be useful to have scratch space.  The
 282   // requestor promises to allocate no more than "max_alloc_words" in any
 283   // older generation (via promotion say.)   Any blocks of space that can
 284   // be provided are returned as a list of ScratchBlocks, sorted by
 285   // decreasing size.
 286   ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
 287   // Allow each generation to reset any scratch space that it has
 288   // contributed as it needs.
 289   void release_scratch();
 290 
 291   // Ensure parsability: override
 292   virtual void ensure_parsability(bool retire_tlabs);
 293 
 294   // Time in ms since the longest time a collector ran in
 295   // in any generation.
 296   virtual jlong millis_since_last_gc();
 297 
 298   // Total number of full collections completed.
 299   unsigned int total_full_collections_completed() {
 300     assert(_full_collections_completed <= _total_full_collections,
 301            "Can't complete more collections than were started");
 302     return _full_collections_completed;
 303   }
 304 
 305   // Update above counter, as appropriate, at the end of a stop-world GC cycle
 306   unsigned int update_full_collections_completed();
 307   // Update above counter, as appropriate, at the end of a concurrent GC cycle
 308   unsigned int update_full_collections_completed(unsigned int count);
 309 
 310   // Update "time of last gc" for all constituent generations
 311   // to "now".
 312   void update_time_of_last_gc(jlong now) {
 313     for (int i = 0; i < _n_gens; i++) {
 314       _gens[i]->update_time_of_last_gc(now);
 315     }
 316   }
 317 
 318   // Update the gc statistics for each generation.
 319   // "level" is the level of the latest collection.
 320   void update_gc_stats(int current_level, bool full) {
 321     for (int i = 0; i < _n_gens; i++) {
 322       _gens[i]->update_gc_stats(current_level, full);
 323     }
 324   }
 325 
 326   // Override.
 327   bool no_gc_in_progress() { return !is_gc_active(); }
 328 
 329   // Override.
 330   void prepare_for_verify();
 331 
 332   // Override.
 333   void verify(bool silent, VerifyOption option);
 334 
 335   // Override.
 336   virtual void print_on(outputStream* st) const;
 337   virtual void print_gc_threads_on(outputStream* st) const;
 338   virtual void gc_threads_do(ThreadClosure* tc) const;
 339   virtual void print_tracing_info() const;
 340   virtual void print_on_error(outputStream* st) const;
 341 
 342   // PrintGC, PrintGCDetails support
 343   void print_heap_change(size_t prev_used) const;
 344 
 345   // The functions below are helper functions that a subclass of
 346   // "CollectedHeap" can use in the implementation of its virtual
 347   // functions.
 348 
 349   class GenClosure : public StackObj {
 350    public:
 351     virtual void do_generation(Generation* gen) = 0;
 352   };
 353 
 354   // Apply "cl.do_generation" to all generations in the heap
 355   // If "old_to_young" determines the order.
 356   void generation_iterate(GenClosure* cl, bool old_to_young);
 357 
 358   void space_iterate(SpaceClosure* cl);
 359 
 360   // Return "true" if all generations have reached the
 361   // maximal committed limit that they can reach, without a garbage
 362   // collection.
 363   virtual bool is_maximal_no_gc() const;
 364 
 365   // Return the generation before "gen".
 366   Generation* prev_gen(Generation* gen) const {
 367     int l = gen->level();
 368     guarantee(l > 0, "Out of bounds");
 369     return _gens[l-1];
 370   }
 371 
 372   // Return the generation after "gen".
 373   Generation* next_gen(Generation* gen) const {
 374     int l = gen->level() + 1;
 375     guarantee(l < _n_gens, "Out of bounds");
 376     return _gens[l];
 377   }
 378 
 379   Generation* get_gen(int i) const {
 380     guarantee(i >= 0 && i < _n_gens, "Out of bounds");
 381     return _gens[i];
 382   }
 383 
 384   int n_gens() const {
 385     assert(_n_gens == gen_policy()->number_of_generations(), "Sanity");
 386     return _n_gens;
 387   }
 388 
 389   // This function returns the "GenRemSet" object that allows us to scan
 390   // generations in a fully generational heap.
 391   GenRemSet* rem_set() { return _rem_set; }
 392 
 393   // Convenience function to be used in situations where the heap type can be
 394   // asserted to be this type.
 395   static GenCollectedHeap* heap();
 396 
 397   void set_par_threads(uint t);
 398 
 399   // Invoke the "do_oop" method of one of the closures "not_older_gens"
 400   // or "older_gens" on root locations for the generation at
 401   // "level".  (The "older_gens" closure is used for scanning references
 402   // from older generations; "not_older_gens" is used everywhere else.)
 403   // If "younger_gens_as_roots" is false, younger generations are
 404   // not scanned as roots; in this case, the caller must be arranging to
 405   // scan the younger generations itself.  (For example, a generation might
 406   // explicitly mark reachable objects in younger generations, to avoid
 407   // excess storage retention.)
 408   // The "so" argument determines which of the roots
 409   // the closure is applied to:
 410   // "SO_None" does none;
 411  private:
 412   void gen_process_roots(int level,
 413                          bool younger_gens_as_roots,
 414                          bool activate_scope,
 415                          SharedHeap::ScanningOption so,
 416                          OopsInGenClosure* not_older_gens,
 417                          OopsInGenClosure* weak_roots,
 418                          OopsInGenClosure* older_gens,
 419                          CLDClosure* cld_closure,
 420                          CLDClosure* weak_cld_closure,
 421                          CodeBlobClosure* code_closure);
 422 
 423  public:
 424   static const bool StrongAndWeakRoots = false;
 425   static const bool StrongRootsOnly    = true;
 426 
 427   void gen_process_roots(int level,
 428                          bool younger_gens_as_roots,
 429                          bool activate_scope,
 430                          SharedHeap::ScanningOption so,
 431                          bool only_strong_roots,
 432                          OopsInGenClosure* not_older_gens,
 433                          OopsInGenClosure* older_gens,
 434                          CLDClosure* cld_closure);
 435 
 436   // Apply "root_closure" to all the weak roots of the system.
 437   // These include JNI weak roots, string table,
 438   // and referents of reachable weak refs.
 439   void gen_process_weak_roots(OopClosure* root_closure);
 440 
 441   // Set the saved marks of generations, if that makes sense.
 442   // In particular, if any generation might iterate over the oops
 443   // in other generations, it should call this method.
 444   void save_marks();
 445 
 446   // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
 447   // allocated since the last call to save_marks in generations at or above
 448   // "level".  The "cur" closure is
 449   // applied to references in the generation at "level", and the "older"
 450   // closure to older generations.
 451 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix)    \
 452   void oop_since_save_marks_iterate(int level,                          \
 453                                     OopClosureType* cur,                \
 454                                     OopClosureType* older);
 455 
 456   ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
 457 
 458 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
 459 
 460   // Returns "true" iff no allocations have occurred in any generation at
 461   // "level" or above since the last
 462   // call to "save_marks".
 463   bool no_allocs_since_save_marks(int level);
 464 
 465   // Returns true if an incremental collection is likely to fail.
 466   // We optionally consult the young gen, if asked to do so;
 467   // otherwise we base our answer on whether the previous incremental
 468   // collection attempt failed with no corrective action as of yet.
 469   bool incremental_collection_will_fail(bool consult_young) {
 470     // Assumes a 2-generation system; the first disjunct remembers if an
 471     // incremental collection failed, even when we thought (second disjunct)
 472     // that it would not.
 473     assert(heap()->collector_policy()->is_generation_policy(),
 474            "the following definition may not be suitable for an n(>2)-generation system");
 475     return incremental_collection_failed() ||
 476            (consult_young && !get_gen(0)->collection_attempt_is_safe());
 477   }
 478 
 479   // If a generation bails out of an incremental collection,
 480   // it sets this flag.
 481   bool incremental_collection_failed() const {
 482     return _incremental_collection_failed;
 483   }
 484   void set_incremental_collection_failed() {
 485     _incremental_collection_failed = true;
 486   }
 487   void clear_incremental_collection_failed() {
 488     _incremental_collection_failed = false;
 489   }
 490 
 491   // Promotion of obj into gen failed.  Try to promote obj to higher
 492   // gens in ascending order; return the new location of obj if successful.
 493   // Otherwise, try expand-and-allocate for obj in both the young and old
 494   // generation; return the new location of obj if successful.  Otherwise, return NULL.
 495   oop handle_failed_promotion(Generation* old_gen,
 496                               oop obj,
 497                               size_t obj_size);
 498 
 499 private:
 500   // Accessor for memory state verification support
 501   NOT_PRODUCT(
 502     static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
 503   )
 504 
 505   // Override
 506   void check_for_non_bad_heap_word_value(HeapWord* addr,
 507     size_t size) PRODUCT_RETURN;
 508 
 509   // For use by mark-sweep.  As implemented, mark-sweep-compact is global
 510   // in an essential way: compaction is performed across generations, by
 511   // iterating over spaces.
 512   void prepare_for_compaction();
 513 
 514   // Perform a full collection of the first max_level+1 generations.
 515   // This is the low level interface used by the public versions of
 516   // collect() and collect_locked(). Caller holds the Heap_lock on entry.
 517   void collect_locked(GCCause::Cause cause, int max_level);
 518 
 519   // Returns success or failure.
 520   bool create_cms_collector();
 521 
 522   // In support of ExplicitGCInvokesConcurrent functionality
 523   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 524   void collect_mostly_concurrent(GCCause::Cause cause);
 525 
 526   // Save the tops of the spaces in all generations
 527   void record_gen_tops_before_GC() PRODUCT_RETURN;
 528 
 529 protected:
 530   virtual void gc_prologue(bool full);
 531   virtual void gc_epilogue(bool full);
 532 };
 533 
 534 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP