rev 5918 : 8035326: Assume non-NULL references in G1CollectedHeap::in_cset_fast_test
Summary: Remove the assumption that G1CollectedHeap::in_cset_fast_test needs to check for NULL references. Most of the time this is not required, making the code doing this check multiple times.
Reviewed-by:
rev 5919 : 8035329: Move G1ParCopyClosure::copy_to_survivor_space into G1ParScanThreadState
Summary: Move G1ParCopyClosure::copy_to_survivor_space to decrease code size.

   1 /*
   2  * Copyright (c) 2001, 2013, 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
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  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
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  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  27 
  28 #include "gc_implementation/g1/concurrentMark.hpp"
  29 #include "gc_implementation/g1/evacuationInfo.hpp"
  30 #include "gc_implementation/g1/g1AllocRegion.hpp"
  31 #include "gc_implementation/g1/g1HRPrinter.hpp"
  32 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
  33 #include "gc_implementation/g1/g1RemSet.hpp"
  34 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
  35 #include "gc_implementation/g1/g1YCTypes.hpp"
  36 #include "gc_implementation/g1/heapRegionSeq.hpp"
  37 #include "gc_implementation/g1/heapRegionSets.hpp"
  38 #include "gc_implementation/shared/hSpaceCounters.hpp"
  39 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
  40 #include "memory/barrierSet.hpp"
  41 #include "memory/memRegion.hpp"
  42 #include "memory/sharedHeap.hpp"
  43 #include "utilities/stack.hpp"
  44 
  45 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  46 // It uses the "Garbage First" heap organization and algorithm, which
  47 // may combine concurrent marking with parallel, incremental compaction of
  48 // heap subsets that will yield large amounts of garbage.
  49 
  50 // Forward declarations
  51 class HeapRegion;
  52 class HRRSCleanupTask;
  53 class GenerationSpec;
  54 class OopsInHeapRegionClosure;
  55 class G1KlassScanClosure;
  56 class G1ScanHeapEvacClosure;
  57 class ObjectClosure;
  58 class SpaceClosure;
  59 class CompactibleSpaceClosure;
  60 class Space;
  61 class G1CollectorPolicy;
  62 class GenRemSet;
  63 class G1RemSet;
  64 class HeapRegionRemSetIterator;
  65 class ConcurrentMark;
  66 class ConcurrentMarkThread;
  67 class ConcurrentG1Refine;
  68 class ConcurrentGCTimer;
  69 class GenerationCounters;
  70 class STWGCTimer;
  71 class G1NewTracer;
  72 class G1OldTracer;
  73 class EvacuationFailedInfo;
  74 class nmethod;
  75 class Ticks;
  76 
  77 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  78 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  79 
  80 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  81 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  82 
  83 enum GCAllocPurpose {
  84   GCAllocForTenured,
  85   GCAllocForSurvived,
  86   GCAllocPurposeCount
  87 };
  88 
  89 class YoungList : public CHeapObj<mtGC> {
  90 private:
  91   G1CollectedHeap* _g1h;
  92 
  93   HeapRegion* _head;
  94 
  95   HeapRegion* _survivor_head;
  96   HeapRegion* _survivor_tail;
  97 
  98   HeapRegion* _curr;
  99 
 100   uint        _length;
 101   uint        _survivor_length;
 102 
 103   size_t      _last_sampled_rs_lengths;
 104   size_t      _sampled_rs_lengths;
 105 
 106   void         empty_list(HeapRegion* list);
 107 
 108 public:
 109   YoungList(G1CollectedHeap* g1h);
 110 
 111   void         push_region(HeapRegion* hr);
 112   void         add_survivor_region(HeapRegion* hr);
 113 
 114   void         empty_list();
 115   bool         is_empty() { return _length == 0; }
 116   uint         length() { return _length; }
 117   uint         survivor_length() { return _survivor_length; }
 118 
 119   // Currently we do not keep track of the used byte sum for the
 120   // young list and the survivors and it'd be quite a lot of work to
 121   // do so. When we'll eventually replace the young list with
 122   // instances of HeapRegionLinkedList we'll get that for free. So,
 123   // we'll report the more accurate information then.
 124   size_t       eden_used_bytes() {
 125     assert(length() >= survivor_length(), "invariant");
 126     return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
 127   }
 128   size_t       survivor_used_bytes() {
 129     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 130   }
 131 
 132   void rs_length_sampling_init();
 133   bool rs_length_sampling_more();
 134   void rs_length_sampling_next();
 135 
 136   void reset_sampled_info() {
 137     _last_sampled_rs_lengths =   0;
 138   }
 139   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 140 
 141   // for development purposes
 142   void reset_auxilary_lists();
 143   void clear() { _head = NULL; _length = 0; }
 144 
 145   void clear_survivors() {
 146     _survivor_head    = NULL;
 147     _survivor_tail    = NULL;
 148     _survivor_length  = 0;
 149   }
 150 
 151   HeapRegion* first_region() { return _head; }
 152   HeapRegion* first_survivor_region() { return _survivor_head; }
 153   HeapRegion* last_survivor_region() { return _survivor_tail; }
 154 
 155   // debugging
 156   bool          check_list_well_formed();
 157   bool          check_list_empty(bool check_sample = true);
 158   void          print();
 159 };
 160 
 161 class MutatorAllocRegion : public G1AllocRegion {
 162 protected:
 163   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 164   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 165 public:
 166   MutatorAllocRegion()
 167     : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
 168 };
 169 
 170 class SurvivorGCAllocRegion : public G1AllocRegion {
 171 protected:
 172   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 173   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 174 public:
 175   SurvivorGCAllocRegion()
 176   : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { }
 177 };
 178 
 179 class OldGCAllocRegion : public G1AllocRegion {
 180 protected:
 181   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 182   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 183 public:
 184   OldGCAllocRegion()
 185   : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { }
 186 };
 187 
 188 // The G1 STW is alive closure.
 189 // An instance is embedded into the G1CH and used as the
 190 // (optional) _is_alive_non_header closure in the STW
 191 // reference processor. It is also extensively used during
 192 // reference processing during STW evacuation pauses.
 193 class G1STWIsAliveClosure: public BoolObjectClosure {
 194   G1CollectedHeap* _g1;
 195 public:
 196   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 197   bool do_object_b(oop p);
 198 };
 199 
 200 class RefineCardTableEntryClosure;
 201 
 202 class G1CollectedHeap : public SharedHeap {
 203   friend class VM_G1CollectForAllocation;
 204   friend class VM_G1CollectFull;
 205   friend class VM_G1IncCollectionPause;
 206   friend class VMStructs;
 207   friend class MutatorAllocRegion;
 208   friend class SurvivorGCAllocRegion;
 209   friend class OldGCAllocRegion;
 210 
 211   // Closures used in implementation.
 212   template <G1Barrier barrier, bool do_mark_object>
 213   friend class G1ParCopyClosure;
 214   friend class G1IsAliveClosure;
 215   friend class G1EvacuateFollowersClosure;
 216   friend class G1ParScanThreadState;
 217   friend class G1ParScanClosureSuper;
 218   friend class G1ParEvacuateFollowersClosure;
 219   friend class G1ParTask;
 220   friend class G1FreeGarbageRegionClosure;
 221   friend class RefineCardTableEntryClosure;
 222   friend class G1PrepareCompactClosure;
 223   friend class RegionSorter;
 224   friend class RegionResetter;
 225   friend class CountRCClosure;
 226   friend class EvacPopObjClosure;
 227   friend class G1ParCleanupCTTask;
 228 
 229   // Other related classes.
 230   friend class G1MarkSweep;
 231 
 232 private:
 233   // The one and only G1CollectedHeap, so static functions can find it.
 234   static G1CollectedHeap* _g1h;
 235 
 236   static size_t _humongous_object_threshold_in_words;
 237 
 238   // Storage for the G1 heap.
 239   VirtualSpace _g1_storage;
 240   MemRegion    _g1_reserved;
 241 
 242   // The part of _g1_storage that is currently committed.
 243   MemRegion _g1_committed;
 244 
 245   // The master free list. It will satisfy all new region allocations.
 246   MasterFreeRegionList      _free_list;
 247 
 248   // The secondary free list which contains regions that have been
 249   // freed up during the cleanup process. This will be appended to the
 250   // master free list when appropriate.
 251   SecondaryFreeRegionList   _secondary_free_list;
 252 
 253   // It keeps track of the old regions.
 254   MasterOldRegionSet        _old_set;
 255 
 256   // It keeps track of the humongous regions.
 257   MasterHumongousRegionSet  _humongous_set;
 258 
 259   // The number of regions we could create by expansion.
 260   uint _expansion_regions;
 261 
 262   // The block offset table for the G1 heap.
 263   G1BlockOffsetSharedArray* _bot_shared;
 264 
 265   // Tears down the region sets / lists so that they are empty and the
 266   // regions on the heap do not belong to a region set / list. The
 267   // only exception is the humongous set which we leave unaltered. If
 268   // free_list_only is true, it will only tear down the master free
 269   // list. It is called before a Full GC (free_list_only == false) or
 270   // before heap shrinking (free_list_only == true).
 271   void tear_down_region_sets(bool free_list_only);
 272 
 273   // Rebuilds the region sets / lists so that they are repopulated to
 274   // reflect the contents of the heap. The only exception is the
 275   // humongous set which was not torn down in the first place. If
 276   // free_list_only is true, it will only rebuild the master free
 277   // list. It is called after a Full GC (free_list_only == false) or
 278   // after heap shrinking (free_list_only == true).
 279   void rebuild_region_sets(bool free_list_only);
 280 
 281   // The sequence of all heap regions in the heap.
 282   HeapRegionSeq _hrs;
 283 
 284   // Alloc region used to satisfy mutator allocation requests.
 285   MutatorAllocRegion _mutator_alloc_region;
 286 
 287   // Alloc region used to satisfy allocation requests by the GC for
 288   // survivor objects.
 289   SurvivorGCAllocRegion _survivor_gc_alloc_region;
 290 
 291   // PLAB sizing policy for survivors.
 292   PLABStats _survivor_plab_stats;
 293 
 294   // Alloc region used to satisfy allocation requests by the GC for
 295   // old objects.
 296   OldGCAllocRegion _old_gc_alloc_region;
 297 
 298   // PLAB sizing policy for tenured objects.
 299   PLABStats _old_plab_stats;
 300 
 301   PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
 302     PLABStats* stats = NULL;
 303 
 304     switch (purpose) {
 305     case GCAllocForSurvived:
 306       stats = &_survivor_plab_stats;
 307       break;
 308     case GCAllocForTenured:
 309       stats = &_old_plab_stats;
 310       break;
 311     default:
 312       assert(false, "unrecognized GCAllocPurpose");
 313     }
 314 
 315     return stats;
 316   }
 317 
 318   // The last old region we allocated to during the last GC.
 319   // Typically, it is not full so we should re-use it during the next GC.
 320   HeapRegion* _retained_old_gc_alloc_region;
 321 
 322   // It specifies whether we should attempt to expand the heap after a
 323   // region allocation failure. If heap expansion fails we set this to
 324   // false so that we don't re-attempt the heap expansion (it's likely
 325   // that subsequent expansion attempts will also fail if one fails).
 326   // Currently, it is only consulted during GC and it's reset at the
 327   // start of each GC.
 328   bool _expand_heap_after_alloc_failure;
 329 
 330   // It resets the mutator alloc region before new allocations can take place.
 331   void init_mutator_alloc_region();
 332 
 333   // It releases the mutator alloc region.
 334   void release_mutator_alloc_region();
 335 
 336   // It initializes the GC alloc regions at the start of a GC.
 337   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 338 
 339   // It releases the GC alloc regions at the end of a GC.
 340   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 341 
 342   // It does any cleanup that needs to be done on the GC alloc regions
 343   // before a Full GC.
 344   void abandon_gc_alloc_regions();
 345 
 346   // Helper for monitoring and management support.
 347   G1MonitoringSupport* _g1mm;
 348 
 349   // Determines PLAB size for a particular allocation purpose.
 350   size_t desired_plab_sz(GCAllocPurpose purpose);
 351 
 352   // Outside of GC pauses, the number of bytes used in all regions other
 353   // than the current allocation region.
 354   size_t _summary_bytes_used;
 355 
 356   // This is used for a quick test on whether a reference points into
 357   // the collection set or not. Basically, we have an array, with one
 358   // byte per region, and that byte denotes whether the corresponding
 359   // region is in the collection set or not. The entry corresponding
 360   // the bottom of the heap, i.e., region 0, is pointed to by
 361   // _in_cset_fast_test_base.  The _in_cset_fast_test field has been
 362   // biased so that it actually points to address 0 of the address
 363   // space, to make the test as fast as possible (we can simply shift
 364   // the address to address into it, instead of having to subtract the
 365   // bottom of the heap from the address before shifting it; basically
 366   // it works in the same way the card table works).
 367   bool* _in_cset_fast_test;
 368 
 369   // The allocated array used for the fast test on whether a reference
 370   // points into the collection set or not. This field is also used to
 371   // free the array.
 372   bool* _in_cset_fast_test_base;
 373 
 374   // The length of the _in_cset_fast_test_base array.
 375   uint _in_cset_fast_test_length;
 376 
 377   volatile unsigned _gc_time_stamp;
 378 
 379   size_t* _surviving_young_words;
 380 
 381   G1HRPrinter _hr_printer;
 382 
 383   void setup_surviving_young_words();
 384   void update_surviving_young_words(size_t* surv_young_words);
 385   void cleanup_surviving_young_words();
 386 
 387   // It decides whether an explicit GC should start a concurrent cycle
 388   // instead of doing a STW GC. Currently, a concurrent cycle is
 389   // explicitly started if:
 390   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 391   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 392   // (c) cause == _g1_humongous_allocation
 393   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 394 
 395   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 396   // concurrent cycles) we have started.
 397   volatile unsigned int _old_marking_cycles_started;
 398 
 399   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 400   // concurrent cycles) we have completed.
 401   volatile unsigned int _old_marking_cycles_completed;
 402 
 403   bool _concurrent_cycle_started;
 404 
 405   // This is a non-product method that is helpful for testing. It is
 406   // called at the end of a GC and artificially expands the heap by
 407   // allocating a number of dead regions. This way we can induce very
 408   // frequent marking cycles and stress the cleanup / concurrent
 409   // cleanup code more (as all the regions that will be allocated by
 410   // this method will be found dead by the marking cycle).
 411   void allocate_dummy_regions() PRODUCT_RETURN;
 412 
 413   // Clear RSets after a compaction. It also resets the GC time stamps.
 414   void clear_rsets_post_compaction();
 415 
 416   // If the HR printer is active, dump the state of the regions in the
 417   // heap after a compaction.
 418   void print_hrs_post_compaction();
 419 
 420   double verify(bool guard, const char* msg);
 421   void verify_before_gc();
 422   void verify_after_gc();
 423 
 424   void log_gc_header();
 425   void log_gc_footer(double pause_time_sec);
 426 
 427   // These are macros so that, if the assert fires, we get the correct
 428   // line number, file, etc.
 429 
 430 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 431   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 432           (_extra_message_),                                                  \
 433           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 434           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 435           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 436 
 437 #define assert_heap_locked()                                                  \
 438   do {                                                                        \
 439     assert(Heap_lock->owned_by_self(),                                        \
 440            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 441   } while (0)
 442 
 443 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 444   do {                                                                        \
 445     assert(Heap_lock->owned_by_self() ||                                      \
 446            (SafepointSynchronize::is_at_safepoint() &&                        \
 447              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 448            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 449                                         "should be at a safepoint"));         \
 450   } while (0)
 451 
 452 #define assert_heap_locked_and_not_at_safepoint()                             \
 453   do {                                                                        \
 454     assert(Heap_lock->owned_by_self() &&                                      \
 455                                     !SafepointSynchronize::is_at_safepoint(), \
 456           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 457                                        "should not be at a safepoint"));      \
 458   } while (0)
 459 
 460 #define assert_heap_not_locked()                                              \
 461   do {                                                                        \
 462     assert(!Heap_lock->owned_by_self(),                                       \
 463         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 464   } while (0)
 465 
 466 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 467   do {                                                                        \
 468     assert(!Heap_lock->owned_by_self() &&                                     \
 469                                     !SafepointSynchronize::is_at_safepoint(), \
 470       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 471                                    "should not be at a safepoint"));          \
 472   } while (0)
 473 
 474 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 475   do {                                                                        \
 476     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 477               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 478            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 479   } while (0)
 480 
 481 #define assert_not_at_safepoint()                                             \
 482   do {                                                                        \
 483     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 484            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 485   } while (0)
 486 
 487 protected:
 488 
 489   // The young region list.
 490   YoungList*  _young_list;
 491 
 492   // The current policy object for the collector.
 493   G1CollectorPolicy* _g1_policy;
 494 
 495   // This is the second level of trying to allocate a new region. If
 496   // new_region() didn't find a region on the free_list, this call will
 497   // check whether there's anything available on the
 498   // secondary_free_list and/or wait for more regions to appear on
 499   // that list, if _free_regions_coming is set.
 500   HeapRegion* new_region_try_secondary_free_list();
 501 
 502   // Try to allocate a single non-humongous HeapRegion sufficient for
 503   // an allocation of the given word_size. If do_expand is true,
 504   // attempt to expand the heap if necessary to satisfy the allocation
 505   // request.
 506   HeapRegion* new_region(size_t word_size, bool do_expand);
 507 
 508   // Attempt to satisfy a humongous allocation request of the given
 509   // size by finding a contiguous set of free regions of num_regions
 510   // length and remove them from the master free list. Return the
 511   // index of the first region or G1_NULL_HRS_INDEX if the search
 512   // was unsuccessful.
 513   uint humongous_obj_allocate_find_first(uint num_regions,
 514                                          size_t word_size);
 515 
 516   // Initialize a contiguous set of free regions of length num_regions
 517   // and starting at index first so that they appear as a single
 518   // humongous region.
 519   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 520                                                       uint num_regions,
 521                                                       size_t word_size);
 522 
 523   // Attempt to allocate a humongous object of the given size. Return
 524   // NULL if unsuccessful.
 525   HeapWord* humongous_obj_allocate(size_t word_size);
 526 
 527   // The following two methods, allocate_new_tlab() and
 528   // mem_allocate(), are the two main entry points from the runtime
 529   // into the G1's allocation routines. They have the following
 530   // assumptions:
 531   //
 532   // * They should both be called outside safepoints.
 533   //
 534   // * They should both be called without holding the Heap_lock.
 535   //
 536   // * All allocation requests for new TLABs should go to
 537   //   allocate_new_tlab().
 538   //
 539   // * All non-TLAB allocation requests should go to mem_allocate().
 540   //
 541   // * If either call cannot satisfy the allocation request using the
 542   //   current allocating region, they will try to get a new one. If
 543   //   this fails, they will attempt to do an evacuation pause and
 544   //   retry the allocation.
 545   //
 546   // * If all allocation attempts fail, even after trying to schedule
 547   //   an evacuation pause, allocate_new_tlab() will return NULL,
 548   //   whereas mem_allocate() will attempt a heap expansion and/or
 549   //   schedule a Full GC.
 550   //
 551   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 552   //   should never be called with word_size being humongous. All
 553   //   humongous allocation requests should go to mem_allocate() which
 554   //   will satisfy them with a special path.
 555 
 556   virtual HeapWord* allocate_new_tlab(size_t word_size);
 557 
 558   virtual HeapWord* mem_allocate(size_t word_size,
 559                                  bool*  gc_overhead_limit_was_exceeded);
 560 
 561   // The following three methods take a gc_count_before_ret
 562   // parameter which is used to return the GC count if the method
 563   // returns NULL. Given that we are required to read the GC count
 564   // while holding the Heap_lock, and these paths will take the
 565   // Heap_lock at some point, it's easier to get them to read the GC
 566   // count while holding the Heap_lock before they return NULL instead
 567   // of the caller (namely: mem_allocate()) having to also take the
 568   // Heap_lock just to read the GC count.
 569 
 570   // First-level mutator allocation attempt: try to allocate out of
 571   // the mutator alloc region without taking the Heap_lock. This
 572   // should only be used for non-humongous allocations.
 573   inline HeapWord* attempt_allocation(size_t word_size,
 574                                       unsigned int* gc_count_before_ret,
 575                                       int* gclocker_retry_count_ret);
 576 
 577   // Second-level mutator allocation attempt: take the Heap_lock and
 578   // retry the allocation attempt, potentially scheduling a GC
 579   // pause. This should only be used for non-humongous allocations.
 580   HeapWord* attempt_allocation_slow(size_t word_size,
 581                                     unsigned int* gc_count_before_ret,
 582                                     int* gclocker_retry_count_ret);
 583 
 584   // Takes the Heap_lock and attempts a humongous allocation. It can
 585   // potentially schedule a GC pause.
 586   HeapWord* attempt_allocation_humongous(size_t word_size,
 587                                          unsigned int* gc_count_before_ret,
 588                                          int* gclocker_retry_count_ret);
 589 
 590   // Allocation attempt that should be called during safepoints (e.g.,
 591   // at the end of a successful GC). expect_null_mutator_alloc_region
 592   // specifies whether the mutator alloc region is expected to be NULL
 593   // or not.
 594   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 595                                        bool expect_null_mutator_alloc_region);
 596 
 597   // It dirties the cards that cover the block so that so that the post
 598   // write barrier never queues anything when updating objects on this
 599   // block. It is assumed (and in fact we assert) that the block
 600   // belongs to a young region.
 601   inline void dirty_young_block(HeapWord* start, size_t word_size);
 602 
 603   // Allocate blocks during garbage collection. Will ensure an
 604   // allocation region, either by picking one or expanding the
 605   // heap, and then allocate a block of the given size. The block
 606   // may not be a humongous - it must fit into a single heap region.
 607   HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
 608 
 609   // Ensure that no further allocations can happen in "r", bearing in mind
 610   // that parallel threads might be attempting allocations.
 611   void par_allocate_remaining_space(HeapRegion* r);
 612 
 613   // Allocation attempt during GC for a survivor object / PLAB.
 614   inline HeapWord* survivor_attempt_allocation(size_t word_size);
 615 
 616   // Allocation attempt during GC for an old object / PLAB.
 617   inline HeapWord* old_attempt_allocation(size_t word_size);
 618 
 619   // These methods are the "callbacks" from the G1AllocRegion class.
 620 
 621   // For mutator alloc regions.
 622   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 623   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 624                                    size_t allocated_bytes);
 625 
 626   // For GC alloc regions.
 627   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 628                                   GCAllocPurpose ap);
 629   void retire_gc_alloc_region(HeapRegion* alloc_region,
 630                               size_t allocated_bytes, GCAllocPurpose ap);
 631 
 632   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 633   //   inspection request and should collect the entire heap
 634   // - if clear_all_soft_refs is true, all soft references should be
 635   //   cleared during the GC
 636   // - if explicit_gc is false, word_size describes the allocation that
 637   //   the GC should attempt (at least) to satisfy
 638   // - it returns false if it is unable to do the collection due to the
 639   //   GC locker being active, true otherwise
 640   bool do_collection(bool explicit_gc,
 641                      bool clear_all_soft_refs,
 642                      size_t word_size);
 643 
 644   // Callback from VM_G1CollectFull operation.
 645   // Perform a full collection.
 646   virtual void do_full_collection(bool clear_all_soft_refs);
 647 
 648   // Resize the heap if necessary after a full collection.  If this is
 649   // after a collect-for allocation, "word_size" is the allocation size,
 650   // and will be considered part of the used portion of the heap.
 651   void resize_if_necessary_after_full_collection(size_t word_size);
 652 
 653   // Callback from VM_G1CollectForAllocation operation.
 654   // This function does everything necessary/possible to satisfy a
 655   // failed allocation request (including collection, expansion, etc.)
 656   HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
 657 
 658   // Attempting to expand the heap sufficiently
 659   // to support an allocation of the given "word_size".  If
 660   // successful, perform the allocation and return the address of the
 661   // allocated block, or else "NULL".
 662   HeapWord* expand_and_allocate(size_t word_size);
 663 
 664   // Process any reference objects discovered during
 665   // an incremental evacuation pause.
 666   void process_discovered_references(uint no_of_gc_workers);
 667 
 668   // Enqueue any remaining discovered references
 669   // after processing.
 670   void enqueue_discovered_references(uint no_of_gc_workers);
 671 
 672 public:
 673 
 674   G1MonitoringSupport* g1mm() {
 675     assert(_g1mm != NULL, "should have been initialized");
 676     return _g1mm;
 677   }
 678 
 679   // Expand the garbage-first heap by at least the given size (in bytes!).
 680   // Returns true if the heap was expanded by the requested amount;
 681   // false otherwise.
 682   // (Rounds up to a HeapRegion boundary.)
 683   bool expand(size_t expand_bytes);
 684 
 685   // Do anything common to GC's.
 686   virtual void gc_prologue(bool full);
 687   virtual void gc_epilogue(bool full);
 688 
 689   // We register a region with the fast "in collection set" test. We
 690   // simply set to true the array slot corresponding to this region.
 691   void register_region_with_in_cset_fast_test(HeapRegion* r) {
 692     assert(_in_cset_fast_test_base != NULL, "sanity");
 693     assert(r->in_collection_set(), "invariant");
 694     uint index = r->hrs_index();
 695     assert(index < _in_cset_fast_test_length, "invariant");
 696     assert(!_in_cset_fast_test_base[index], "invariant");
 697     _in_cset_fast_test_base[index] = true;
 698   }
 699 
 700   // This is a fast test on whether a reference points into the
 701   // collection set or not. Assume that the reference
 702   // points into the heap.
 703   bool in_cset_fast_test(oop obj) {
 704     assert(_in_cset_fast_test != NULL, "sanity");
 705     assert(_g1_committed.contains((HeapWord*) obj), "");
 706     // no need to subtract the bottom of the heap from obj,
 707     // _in_cset_fast_test is biased
 708     uintx index = cast_from_oop<uintx>(obj) >> HeapRegion::LogOfHRGrainBytes;
 709     bool ret = _in_cset_fast_test[index];
 710     // let's make sure the result is consistent with what the slower
 711     // test returns
 712     assert( ret || !obj_in_cs(obj), "sanity");
 713     assert(!ret ||  obj_in_cs(obj), "sanity");
 714     return ret;
 715   }
 716 
 717   void clear_cset_fast_test() {
 718     assert(_in_cset_fast_test_base != NULL, "sanity");
 719     memset(_in_cset_fast_test_base, false,
 720            (size_t) _in_cset_fast_test_length * sizeof(bool));
 721   }
 722 
 723   // This is called at the start of either a concurrent cycle or a Full
 724   // GC to update the number of old marking cycles started.
 725   void increment_old_marking_cycles_started();
 726 
 727   // This is called at the end of either a concurrent cycle or a Full
 728   // GC to update the number of old marking cycles completed. Those two
 729   // can happen in a nested fashion, i.e., we start a concurrent
 730   // cycle, a Full GC happens half-way through it which ends first,
 731   // and then the cycle notices that a Full GC happened and ends
 732   // too. The concurrent parameter is a boolean to help us do a bit
 733   // tighter consistency checking in the method. If concurrent is
 734   // false, the caller is the inner caller in the nesting (i.e., the
 735   // Full GC). If concurrent is true, the caller is the outer caller
 736   // in this nesting (i.e., the concurrent cycle). Further nesting is
 737   // not currently supported. The end of this call also notifies
 738   // the FullGCCount_lock in case a Java thread is waiting for a full
 739   // GC to happen (e.g., it called System.gc() with
 740   // +ExplicitGCInvokesConcurrent).
 741   void increment_old_marking_cycles_completed(bool concurrent);
 742 
 743   unsigned int old_marking_cycles_completed() {
 744     return _old_marking_cycles_completed;
 745   }
 746 
 747   void register_concurrent_cycle_start(const Ticks& start_time);
 748   void register_concurrent_cycle_end();
 749   void trace_heap_after_concurrent_cycle();
 750 
 751   G1YCType yc_type();
 752 
 753   G1HRPrinter* hr_printer() { return &_hr_printer; }
 754 
 755 protected:
 756 
 757   // Shrink the garbage-first heap by at most the given size (in bytes!).
 758   // (Rounds down to a HeapRegion boundary.)
 759   virtual void shrink(size_t expand_bytes);
 760   void shrink_helper(size_t expand_bytes);
 761 
 762   #if TASKQUEUE_STATS
 763   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 764   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 765   void reset_taskqueue_stats();
 766   #endif // TASKQUEUE_STATS
 767 
 768   // Schedule the VM operation that will do an evacuation pause to
 769   // satisfy an allocation request of word_size. *succeeded will
 770   // return whether the VM operation was successful (it did do an
 771   // evacuation pause) or not (another thread beat us to it or the GC
 772   // locker was active). Given that we should not be holding the
 773   // Heap_lock when we enter this method, we will pass the
 774   // gc_count_before (i.e., total_collections()) as a parameter since
 775   // it has to be read while holding the Heap_lock. Currently, both
 776   // methods that call do_collection_pause() release the Heap_lock
 777   // before the call, so it's easy to read gc_count_before just before.
 778   HeapWord* do_collection_pause(size_t         word_size,
 779                                 unsigned int   gc_count_before,
 780                                 bool*          succeeded,
 781                                 GCCause::Cause gc_cause);
 782 
 783   // The guts of the incremental collection pause, executed by the vm
 784   // thread. It returns false if it is unable to do the collection due
 785   // to the GC locker being active, true otherwise
 786   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 787 
 788   // Actually do the work of evacuating the collection set.
 789   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 790 
 791   // The g1 remembered set of the heap.
 792   G1RemSet* _g1_rem_set;
 793 
 794   // A set of cards that cover the objects for which the Rsets should be updated
 795   // concurrently after the collection.
 796   DirtyCardQueueSet _dirty_card_queue_set;
 797 
 798   // The closure used to refine a single card.
 799   RefineCardTableEntryClosure* _refine_cte_cl;
 800 
 801   // A function to check the consistency of dirty card logs.
 802   void check_ct_logs_at_safepoint();
 803 
 804   // A DirtyCardQueueSet that is used to hold cards that contain
 805   // references into the current collection set. This is used to
 806   // update the remembered sets of the regions in the collection
 807   // set in the event of an evacuation failure.
 808   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 809 
 810   // After a collection pause, make the regions in the CS into free
 811   // regions.
 812   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 813 
 814   // Abandon the current collection set without recording policy
 815   // statistics or updating free lists.
 816   void abandon_collection_set(HeapRegion* cs_head);
 817 
 818   // Applies "scan_non_heap_roots" to roots outside the heap,
 819   // "scan_rs" to roots inside the heap (having done "set_region" to
 820   // indicate the region in which the root resides),
 821   // and does "scan_metadata" If "scan_rs" is
 822   // NULL, then this step is skipped.  The "worker_i"
 823   // param is for use with parallel roots processing, and should be
 824   // the "i" of the calling parallel worker thread's work(i) function.
 825   // In the sequential case this param will be ignored.
 826   void g1_process_strong_roots(bool is_scavenging,
 827                                ScanningOption so,
 828                                OopClosure* scan_non_heap_roots,
 829                                OopsInHeapRegionClosure* scan_rs,
 830                                G1KlassScanClosure* scan_klasses,
 831                                int worker_i);
 832 
 833   // Frees a non-humongous region by initializing its contents and
 834   // adding it to the free list that's passed as a parameter (this is
 835   // usually a local list which will be appended to the master free
 836   // list later). The used bytes of freed regions are accumulated in
 837   // pre_used. If par is true, the region's RSet will not be freed
 838   // up. The assumption is that this will be done later.
 839   void free_region(HeapRegion* hr,
 840                    size_t* pre_used,
 841                    FreeRegionList* free_list,
 842                    bool par);
 843 
 844   // Frees a humongous region by collapsing it into individual regions
 845   // and calling free_region() for each of them. The freed regions
 846   // will be added to the free list that's passed as a parameter (this
 847   // is usually a local list which will be appended to the master free
 848   // list later). The used bytes of freed regions are accumulated in
 849   // pre_used. If par is true, the region's RSet will not be freed
 850   // up. The assumption is that this will be done later.
 851   void free_humongous_region(HeapRegion* hr,
 852                              size_t* pre_used,
 853                              FreeRegionList* free_list,
 854                              HumongousRegionSet* humongous_proxy_set,
 855                              bool par);
 856 
 857   // Notifies all the necessary spaces that the committed space has
 858   // been updated (either expanded or shrunk). It should be called
 859   // after _g1_storage is updated.
 860   void update_committed_space(HeapWord* old_end, HeapWord* new_end);
 861 
 862   // The concurrent marker (and the thread it runs in.)
 863   ConcurrentMark* _cm;
 864   ConcurrentMarkThread* _cmThread;
 865   bool _mark_in_progress;
 866 
 867   // The concurrent refiner.
 868   ConcurrentG1Refine* _cg1r;
 869 
 870   // The parallel task queues
 871   RefToScanQueueSet *_task_queues;
 872 
 873   // True iff a evacuation has failed in the current collection.
 874   bool _evacuation_failed;
 875 
 876   EvacuationFailedInfo* _evacuation_failed_info_array;
 877 
 878   // Failed evacuations cause some logical from-space objects to have
 879   // forwarding pointers to themselves.  Reset them.
 880   void remove_self_forwarding_pointers();
 881 
 882   // Together, these store an object with a preserved mark, and its mark value.
 883   Stack<oop, mtGC>     _objs_with_preserved_marks;
 884   Stack<markOop, mtGC> _preserved_marks_of_objs;
 885 
 886   // Preserve the mark of "obj", if necessary, in preparation for its mark
 887   // word being overwritten with a self-forwarding-pointer.
 888   void preserve_mark_if_necessary(oop obj, markOop m);
 889 
 890   // The stack of evac-failure objects left to be scanned.
 891   GrowableArray<oop>*    _evac_failure_scan_stack;
 892   // The closure to apply to evac-failure objects.
 893 
 894   OopsInHeapRegionClosure* _evac_failure_closure;
 895   // Set the field above.
 896   void
 897   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 898     _evac_failure_closure = evac_failure_closure;
 899   }
 900 
 901   // Push "obj" on the scan stack.
 902   void push_on_evac_failure_scan_stack(oop obj);
 903   // Process scan stack entries until the stack is empty.
 904   void drain_evac_failure_scan_stack();
 905   // True iff an invocation of "drain_scan_stack" is in progress; to
 906   // prevent unnecessary recursion.
 907   bool _drain_in_progress;
 908 
 909   // Do any necessary initialization for evacuation-failure handling.
 910   // "cl" is the closure that will be used to process evac-failure
 911   // objects.
 912   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 913   // Do any necessary cleanup for evacuation-failure handling data
 914   // structures.
 915   void finalize_for_evac_failure();
 916 
 917   // An attempt to evacuate "obj" has failed; take necessary steps.
 918   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 919   void handle_evacuation_failure_common(oop obj, markOop m);
 920 
 921 #ifndef PRODUCT
 922   // Support for forcing evacuation failures. Analogous to
 923   // PromotionFailureALot for the other collectors.
 924 
 925   // Records whether G1EvacuationFailureALot should be in effect
 926   // for the current GC
 927   bool _evacuation_failure_alot_for_current_gc;
 928 
 929   // Used to record the GC number for interval checking when
 930   // determining whether G1EvaucationFailureALot is in effect
 931   // for the current GC.
 932   size_t _evacuation_failure_alot_gc_number;
 933 
 934   // Count of the number of evacuations between failures.
 935   volatile size_t _evacuation_failure_alot_count;
 936 
 937   // Set whether G1EvacuationFailureALot should be in effect
 938   // for the current GC (based upon the type of GC and which
 939   // command line flags are set);
 940   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 941                                                   bool during_initial_mark,
 942                                                   bool during_marking);
 943 
 944   inline void set_evacuation_failure_alot_for_current_gc();
 945 
 946   // Return true if it's time to cause an evacuation failure.
 947   inline bool evacuation_should_fail();
 948 
 949   // Reset the G1EvacuationFailureALot counters.  Should be called at
 950   // the end of an evacuation pause in which an evacuation failure occurred.
 951   inline void reset_evacuation_should_fail();
 952 #endif // !PRODUCT
 953 
 954   // ("Weak") Reference processing support.
 955   //
 956   // G1 has 2 instances of the reference processor class. One
 957   // (_ref_processor_cm) handles reference object discovery
 958   // and subsequent processing during concurrent marking cycles.
 959   //
 960   // The other (_ref_processor_stw) handles reference object
 961   // discovery and processing during full GCs and incremental
 962   // evacuation pauses.
 963   //
 964   // During an incremental pause, reference discovery will be
 965   // temporarily disabled for _ref_processor_cm and will be
 966   // enabled for _ref_processor_stw. At the end of the evacuation
 967   // pause references discovered by _ref_processor_stw will be
 968   // processed and discovery will be disabled. The previous
 969   // setting for reference object discovery for _ref_processor_cm
 970   // will be re-instated.
 971   //
 972   // At the start of marking:
 973   //  * Discovery by the CM ref processor is verified to be inactive
 974   //    and it's discovered lists are empty.
 975   //  * Discovery by the CM ref processor is then enabled.
 976   //
 977   // At the end of marking:
 978   //  * Any references on the CM ref processor's discovered
 979   //    lists are processed (possibly MT).
 980   //
 981   // At the start of full GC we:
 982   //  * Disable discovery by the CM ref processor and
 983   //    empty CM ref processor's discovered lists
 984   //    (without processing any entries).
 985   //  * Verify that the STW ref processor is inactive and it's
 986   //    discovered lists are empty.
 987   //  * Temporarily set STW ref processor discovery as single threaded.
 988   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 989   //    field.
 990   //  * Finally enable discovery by the STW ref processor.
 991   //
 992   // The STW ref processor is used to record any discovered
 993   // references during the full GC.
 994   //
 995   // At the end of a full GC we:
 996   //  * Enqueue any reference objects discovered by the STW ref processor
 997   //    that have non-live referents. This has the side-effect of
 998   //    making the STW ref processor inactive by disabling discovery.
 999   //  * Verify that the CM ref processor is still inactive
1000   //    and no references have been placed on it's discovered
1001   //    lists (also checked as a precondition during initial marking).
1002 
1003   // The (stw) reference processor...
1004   ReferenceProcessor* _ref_processor_stw;
1005 
1006   STWGCTimer* _gc_timer_stw;
1007   ConcurrentGCTimer* _gc_timer_cm;
1008 
1009   G1OldTracer* _gc_tracer_cm;
1010   G1NewTracer* _gc_tracer_stw;
1011 
1012   // During reference object discovery, the _is_alive_non_header
1013   // closure (if non-null) is applied to the referent object to
1014   // determine whether the referent is live. If so then the
1015   // reference object does not need to be 'discovered' and can
1016   // be treated as a regular oop. This has the benefit of reducing
1017   // the number of 'discovered' reference objects that need to
1018   // be processed.
1019   //
1020   // Instance of the is_alive closure for embedding into the
1021   // STW reference processor as the _is_alive_non_header field.
1022   // Supplying a value for the _is_alive_non_header field is
1023   // optional but doing so prevents unnecessary additions to
1024   // the discovered lists during reference discovery.
1025   G1STWIsAliveClosure _is_alive_closure_stw;
1026 
1027   // The (concurrent marking) reference processor...
1028   ReferenceProcessor* _ref_processor_cm;
1029 
1030   // Instance of the concurrent mark is_alive closure for embedding
1031   // into the Concurrent Marking reference processor as the
1032   // _is_alive_non_header field. Supplying a value for the
1033   // _is_alive_non_header field is optional but doing so prevents
1034   // unnecessary additions to the discovered lists during reference
1035   // discovery.
1036   G1CMIsAliveClosure _is_alive_closure_cm;
1037 
1038   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1039   HeapRegion** _worker_cset_start_region;
1040 
1041   // Time stamp to validate the regions recorded in the cache
1042   // used by G1CollectedHeap::start_cset_region_for_worker().
1043   // The heap region entry for a given worker is valid iff
1044   // the associated time stamp value matches the current value
1045   // of G1CollectedHeap::_gc_time_stamp.
1046   unsigned int* _worker_cset_start_region_time_stamp;
1047 
1048   enum G1H_process_strong_roots_tasks {
1049     G1H_PS_filter_satb_buffers,
1050     G1H_PS_refProcessor_oops_do,
1051     // Leave this one last.
1052     G1H_PS_NumElements
1053   };
1054 
1055   SubTasksDone* _process_strong_tasks;
1056 
1057   volatile bool _free_regions_coming;
1058 
1059 public:
1060 
1061   SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1062 
1063   void set_refine_cte_cl_concurrency(bool concurrent);
1064 
1065   RefToScanQueue *task_queue(int i) const;
1066 
1067   // A set of cards where updates happened during the GC
1068   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1069 
1070   // A DirtyCardQueueSet that is used to hold cards that contain
1071   // references into the current collection set. This is used to
1072   // update the remembered sets of the regions in the collection
1073   // set in the event of an evacuation failure.
1074   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1075         { return _into_cset_dirty_card_queue_set; }
1076 
1077   // Create a G1CollectedHeap with the specified policy.
1078   // Must call the initialize method afterwards.
1079   // May not return if something goes wrong.
1080   G1CollectedHeap(G1CollectorPolicy* policy);
1081 
1082   // Initialize the G1CollectedHeap to have the initial and
1083   // maximum sizes and remembered and barrier sets
1084   // specified by the policy object.
1085   jint initialize();
1086 
1087   // Return the (conservative) maximum heap alignment for any G1 heap
1088   static size_t conservative_max_heap_alignment();
1089 
1090   // Initialize weak reference processing.
1091   virtual void ref_processing_init();
1092 
1093   void set_par_threads(uint t) {
1094     SharedHeap::set_par_threads(t);
1095     // Done in SharedHeap but oddly there are
1096     // two _process_strong_tasks's in a G1CollectedHeap
1097     // so do it here too.
1098     _process_strong_tasks->set_n_threads(t);
1099   }
1100 
1101   // Set _n_par_threads according to a policy TBD.
1102   void set_par_threads();
1103 
1104   void set_n_termination(int t) {
1105     _process_strong_tasks->set_n_threads(t);
1106   }
1107 
1108   virtual CollectedHeap::Name kind() const {
1109     return CollectedHeap::G1CollectedHeap;
1110   }
1111 
1112   // The current policy object for the collector.
1113   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1114 
1115   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1116 
1117   // Adaptive size policy.  No such thing for g1.
1118   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1119 
1120   // The rem set and barrier set.
1121   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1122 
1123   unsigned get_gc_time_stamp() {
1124     return _gc_time_stamp;
1125   }
1126 
1127   void reset_gc_time_stamp() {
1128     _gc_time_stamp = 0;
1129     OrderAccess::fence();
1130     // Clear the cached CSet starting regions and time stamps.
1131     // Their validity is dependent on the GC timestamp.
1132     clear_cset_start_regions();
1133   }
1134 
1135   void check_gc_time_stamps() PRODUCT_RETURN;
1136 
1137   void increment_gc_time_stamp() {
1138     ++_gc_time_stamp;
1139     OrderAccess::fence();
1140   }
1141 
1142   // Reset the given region's GC timestamp. If it's starts humongous,
1143   // also reset the GC timestamp of its corresponding
1144   // continues humongous regions too.
1145   void reset_gc_time_stamps(HeapRegion* hr);
1146 
1147   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1148                                   DirtyCardQueue* into_cset_dcq,
1149                                   bool concurrent, int worker_i);
1150 
1151   // The shared block offset table array.
1152   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1153 
1154   // Reference Processing accessors
1155 
1156   // The STW reference processor....
1157   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1158 
1159   // The Concurrent Marking reference processor...
1160   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1161 
1162   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1163   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1164 
1165   virtual size_t capacity() const;
1166   virtual size_t used() const;
1167   // This should be called when we're not holding the heap lock. The
1168   // result might be a bit inaccurate.
1169   size_t used_unlocked() const;
1170   size_t recalculate_used() const;
1171 
1172   // These virtual functions do the actual allocation.
1173   // Some heaps may offer a contiguous region for shared non-blocking
1174   // allocation, via inlined code (by exporting the address of the top and
1175   // end fields defining the extent of the contiguous allocation region.)
1176   // But G1CollectedHeap doesn't yet support this.
1177 
1178   virtual bool is_maximal_no_gc() const {
1179     return _g1_storage.uncommitted_size() == 0;
1180   }
1181 
1182   // The total number of regions in the heap.
1183   uint n_regions() { return _hrs.length(); }
1184 
1185   // The max number of regions in the heap.
1186   uint max_regions() { return _hrs.max_length(); }
1187 
1188   // The number of regions that are completely free.
1189   uint free_regions() { return _free_list.length(); }
1190 
1191   // The number of regions that are not completely free.
1192   uint used_regions() { return n_regions() - free_regions(); }
1193 
1194   // The number of regions available for "regular" expansion.
1195   uint expansion_regions() { return _expansion_regions; }
1196 
1197   // Factory method for HeapRegion instances. It will return NULL if
1198   // the allocation fails.
1199   HeapRegion* new_heap_region(uint hrs_index, HeapWord* bottom);
1200 
1201   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1202   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1203   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1204   void verify_dirty_young_regions() PRODUCT_RETURN;
1205 
1206   // verify_region_sets() performs verification over the region
1207   // lists. It will be compiled in the product code to be used when
1208   // necessary (i.e., during heap verification).
1209   void verify_region_sets();
1210 
1211   // verify_region_sets_optional() is planted in the code for
1212   // list verification in non-product builds (and it can be enabled in
1213   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1214 #if HEAP_REGION_SET_FORCE_VERIFY
1215   void verify_region_sets_optional() {
1216     verify_region_sets();
1217   }
1218 #else // HEAP_REGION_SET_FORCE_VERIFY
1219   void verify_region_sets_optional() { }
1220 #endif // HEAP_REGION_SET_FORCE_VERIFY
1221 
1222 #ifdef ASSERT
1223   bool is_on_master_free_list(HeapRegion* hr) {
1224     return hr->containing_set() == &_free_list;
1225   }
1226 
1227   bool is_in_humongous_set(HeapRegion* hr) {
1228     return hr->containing_set() == &_humongous_set;
1229   }
1230 #endif // ASSERT
1231 
1232   // Wrapper for the region list operations that can be called from
1233   // methods outside this class.
1234 
1235   void secondary_free_list_add_as_tail(FreeRegionList* list) {
1236     _secondary_free_list.add_as_tail(list);
1237   }
1238 
1239   void append_secondary_free_list() {
1240     _free_list.add_as_head(&_secondary_free_list);
1241   }
1242 
1243   void append_secondary_free_list_if_not_empty_with_lock() {
1244     // If the secondary free list looks empty there's no reason to
1245     // take the lock and then try to append it.
1246     if (!_secondary_free_list.is_empty()) {
1247       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1248       append_secondary_free_list();
1249     }
1250   }
1251 
1252   void old_set_remove(HeapRegion* hr) {
1253     _old_set.remove(hr);
1254   }
1255 
1256   size_t non_young_capacity_bytes() {
1257     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1258   }
1259 
1260   void set_free_regions_coming();
1261   void reset_free_regions_coming();
1262   bool free_regions_coming() { return _free_regions_coming; }
1263   void wait_while_free_regions_coming();
1264 
1265   // Determine whether the given region is one that we are using as an
1266   // old GC alloc region.
1267   bool is_old_gc_alloc_region(HeapRegion* hr) {
1268     return hr == _retained_old_gc_alloc_region;
1269   }
1270 
1271   // Perform a collection of the heap; intended for use in implementing
1272   // "System.gc".  This probably implies as full a collection as the
1273   // "CollectedHeap" supports.
1274   virtual void collect(GCCause::Cause cause);
1275 
1276   // The same as above but assume that the caller holds the Heap_lock.
1277   void collect_locked(GCCause::Cause cause);
1278 
1279   // True iff an evacuation has failed in the most-recent collection.
1280   bool evacuation_failed() { return _evacuation_failed; }
1281 
1282   // It will free a region if it has allocated objects in it that are
1283   // all dead. It calls either free_region() or
1284   // free_humongous_region() depending on the type of the region that
1285   // is passed to it.
1286   void free_region_if_empty(HeapRegion* hr,
1287                             size_t* pre_used,
1288                             FreeRegionList* free_list,
1289                             OldRegionSet* old_proxy_set,
1290                             HumongousRegionSet* humongous_proxy_set,
1291                             HRRSCleanupTask* hrrs_cleanup_task,
1292                             bool par);
1293 
1294   // It appends the free list to the master free list and updates the
1295   // master humongous list according to the contents of the proxy
1296   // list. It also adjusts the total used bytes according to pre_used
1297   // (if par is true, it will do so by taking the ParGCRareEvent_lock).
1298   void update_sets_after_freeing_regions(size_t pre_used,
1299                                        FreeRegionList* free_list,
1300                                        OldRegionSet* old_proxy_set,
1301                                        HumongousRegionSet* humongous_proxy_set,
1302                                        bool par);
1303 
1304   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1305   virtual bool is_in(const void* p) const;
1306 
1307   // Return "TRUE" iff the given object address is within the collection
1308   // set.
1309   inline bool obj_in_cs(oop obj);
1310 
1311   // Return "TRUE" iff the given object address is in the reserved
1312   // region of g1.
1313   bool is_in_g1_reserved(const void* p) const {
1314     return _g1_reserved.contains(p);
1315   }
1316 
1317   // Returns a MemRegion that corresponds to the space that has been
1318   // reserved for the heap
1319   MemRegion g1_reserved() {
1320     return _g1_reserved;
1321   }
1322 
1323   // Returns a MemRegion that corresponds to the space that has been
1324   // committed in the heap
1325   MemRegion g1_committed() {
1326     return _g1_committed;
1327   }
1328 
1329   virtual bool is_in_closed_subset(const void* p) const;
1330 
1331   G1SATBCardTableModRefBS* g1_barrier_set() {
1332     return (G1SATBCardTableModRefBS*) barrier_set();
1333   }
1334 
1335   // This resets the card table to all zeros.  It is used after
1336   // a collection pause which used the card table to claim cards.
1337   void cleanUpCardTable();
1338 
1339   // Iteration functions.
1340 
1341   // Iterate over all the ref-containing fields of all objects, calling
1342   // "cl.do_oop" on each.
1343   virtual void oop_iterate(ExtendedOopClosure* cl);
1344 
1345   // Same as above, restricted to a memory region.
1346   void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1347 
1348   // Iterate over all objects, calling "cl.do_object" on each.
1349   virtual void object_iterate(ObjectClosure* cl);
1350 
1351   virtual void safe_object_iterate(ObjectClosure* cl) {
1352     object_iterate(cl);
1353   }
1354 
1355   // Iterate over all spaces in use in the heap, in ascending address order.
1356   virtual void space_iterate(SpaceClosure* cl);
1357 
1358   // Iterate over heap regions, in address order, terminating the
1359   // iteration early if the "doHeapRegion" method returns "true".
1360   void heap_region_iterate(HeapRegionClosure* blk) const;
1361 
1362   // Return the region with the given index. It assumes the index is valid.
1363   HeapRegion* region_at(uint index) const { return _hrs.at(index); }
1364 
1365   // Divide the heap region sequence into "chunks" of some size (the number
1366   // of regions divided by the number of parallel threads times some
1367   // overpartition factor, currently 4).  Assumes that this will be called
1368   // in parallel by ParallelGCThreads worker threads with distinct worker
1369   // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1370   // calls will use the same "claim_value", and that that claim value is
1371   // different from the claim_value of any heap region before the start of
1372   // the iteration.  Applies "blk->doHeapRegion" to each of the regions, by
1373   // attempting to claim the first region in each chunk, and, if
1374   // successful, applying the closure to each region in the chunk (and
1375   // setting the claim value of the second and subsequent regions of the
1376   // chunk.)  For now requires that "doHeapRegion" always returns "false",
1377   // i.e., that a closure never attempt to abort a traversal.
1378   void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
1379                                        uint worker,
1380                                        uint no_of_par_workers,
1381                                        jint claim_value);
1382 
1383   // It resets all the region claim values to the default.
1384   void reset_heap_region_claim_values();
1385 
1386   // Resets the claim values of regions in the current
1387   // collection set to the default.
1388   void reset_cset_heap_region_claim_values();
1389 
1390 #ifdef ASSERT
1391   bool check_heap_region_claim_values(jint claim_value);
1392 
1393   // Same as the routine above but only checks regions in the
1394   // current collection set.
1395   bool check_cset_heap_region_claim_values(jint claim_value);
1396 #endif // ASSERT
1397 
1398   // Clear the cached cset start regions and (more importantly)
1399   // the time stamps. Called when we reset the GC time stamp.
1400   void clear_cset_start_regions();
1401 
1402   // Given the id of a worker, obtain or calculate a suitable
1403   // starting region for iterating over the current collection set.
1404   HeapRegion* start_cset_region_for_worker(int worker_i);
1405 
1406   // This is a convenience method that is used by the
1407   // HeapRegionIterator classes to calculate the starting region for
1408   // each worker so that they do not all start from the same region.
1409   HeapRegion* start_region_for_worker(uint worker_i, uint no_of_par_workers);
1410 
1411   // Iterate over the regions (if any) in the current collection set.
1412   void collection_set_iterate(HeapRegionClosure* blk);
1413 
1414   // As above but starting from region r
1415   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1416 
1417   // Returns the first (lowest address) compactible space in the heap.
1418   virtual CompactibleSpace* first_compactible_space();
1419 
1420   // A CollectedHeap will contain some number of spaces.  This finds the
1421   // space containing a given address, or else returns NULL.
1422   virtual Space* space_containing(const void* addr) const;
1423 
1424   // A G1CollectedHeap will contain some number of heap regions.  This
1425   // finds the region containing a given address, or else returns NULL.
1426   template <class T>
1427   inline HeapRegion* heap_region_containing(const T addr) const;
1428 
1429   // Like the above, but requires "addr" to be in the heap (to avoid a
1430   // null-check), and unlike the above, may return an continuing humongous
1431   // region.
1432   template <class T>
1433   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1434 
1435   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1436   // each address in the (reserved) heap is a member of exactly
1437   // one block.  The defining characteristic of a block is that it is
1438   // possible to find its size, and thus to progress forward to the next
1439   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1440   // represent Java objects, or they might be free blocks in a
1441   // free-list-based heap (or subheap), as long as the two kinds are
1442   // distinguishable and the size of each is determinable.
1443 
1444   // Returns the address of the start of the "block" that contains the
1445   // address "addr".  We say "blocks" instead of "object" since some heaps
1446   // may not pack objects densely; a chunk may either be an object or a
1447   // non-object.
1448   virtual HeapWord* block_start(const void* addr) const;
1449 
1450   // Requires "addr" to be the start of a chunk, and returns its size.
1451   // "addr + size" is required to be the start of a new chunk, or the end
1452   // of the active area of the heap.
1453   virtual size_t block_size(const HeapWord* addr) const;
1454 
1455   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1456   // the block is an object.
1457   virtual bool block_is_obj(const HeapWord* addr) const;
1458 
1459   // Does this heap support heap inspection? (+PrintClassHistogram)
1460   virtual bool supports_heap_inspection() const { return true; }
1461 
1462   // Section on thread-local allocation buffers (TLABs)
1463   // See CollectedHeap for semantics.
1464 
1465   bool supports_tlab_allocation() const;
1466   size_t tlab_capacity(Thread* ignored) const;
1467   size_t tlab_used(Thread* ignored) const;
1468   size_t max_tlab_size() const;
1469   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1470 
1471   // Can a compiler initialize a new object without store barriers?
1472   // This permission only extends from the creation of a new object
1473   // via a TLAB up to the first subsequent safepoint. If such permission
1474   // is granted for this heap type, the compiler promises to call
1475   // defer_store_barrier() below on any slow path allocation of
1476   // a new object for which such initializing store barriers will
1477   // have been elided. G1, like CMS, allows this, but should be
1478   // ready to provide a compensating write barrier as necessary
1479   // if that storage came out of a non-young region. The efficiency
1480   // of this implementation depends crucially on being able to
1481   // answer very efficiently in constant time whether a piece of
1482   // storage in the heap comes from a young region or not.
1483   // See ReduceInitialCardMarks.
1484   virtual bool can_elide_tlab_store_barriers() const {
1485     return true;
1486   }
1487 
1488   virtual bool card_mark_must_follow_store() const {
1489     return true;
1490   }
1491 
1492   bool is_in_young(const oop obj) {
1493     HeapRegion* hr = heap_region_containing(obj);
1494     return hr != NULL && hr->is_young();
1495   }
1496 
1497 #ifdef ASSERT
1498   virtual bool is_in_partial_collection(const void* p);
1499 #endif
1500 
1501   virtual bool is_scavengable(const void* addr);
1502 
1503   // We don't need barriers for initializing stores to objects
1504   // in the young gen: for the SATB pre-barrier, there is no
1505   // pre-value that needs to be remembered; for the remembered-set
1506   // update logging post-barrier, we don't maintain remembered set
1507   // information for young gen objects.
1508   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
1509     return is_in_young(new_obj);
1510   }
1511 
1512   // Returns "true" iff the given word_size is "very large".
1513   static bool isHumongous(size_t word_size) {
1514     // Note this has to be strictly greater-than as the TLABs
1515     // are capped at the humongous threshold and we want to
1516     // ensure that we don't try to allocate a TLAB as
1517     // humongous and that we don't allocate a humongous
1518     // object in a TLAB.
1519     return word_size > _humongous_object_threshold_in_words;
1520   }
1521 
1522   // Update mod union table with the set of dirty cards.
1523   void updateModUnion();
1524 
1525   // Set the mod union bits corresponding to the given memRegion.  Note
1526   // that this is always a safe operation, since it doesn't clear any
1527   // bits.
1528   void markModUnionRange(MemRegion mr);
1529 
1530   // Records the fact that a marking phase is no longer in progress.
1531   void set_marking_complete() {
1532     _mark_in_progress = false;
1533   }
1534   void set_marking_started() {
1535     _mark_in_progress = true;
1536   }
1537   bool mark_in_progress() {
1538     return _mark_in_progress;
1539   }
1540 
1541   // Print the maximum heap capacity.
1542   virtual size_t max_capacity() const;
1543 
1544   virtual jlong millis_since_last_gc();
1545 
1546 
1547   // Convenience function to be used in situations where the heap type can be
1548   // asserted to be this type.
1549   static G1CollectedHeap* heap();
1550 
1551   void set_region_short_lived_locked(HeapRegion* hr);
1552   // add appropriate methods for any other surv rate groups
1553 
1554   YoungList* young_list() const { return _young_list; }
1555 
1556   // debugging
1557   bool check_young_list_well_formed() {
1558     return _young_list->check_list_well_formed();
1559   }
1560 
1561   bool check_young_list_empty(bool check_heap,
1562                               bool check_sample = true);
1563 
1564   // *** Stuff related to concurrent marking.  It's not clear to me that so
1565   // many of these need to be public.
1566 
1567   // The functions below are helper functions that a subclass of
1568   // "CollectedHeap" can use in the implementation of its virtual
1569   // functions.
1570   // This performs a concurrent marking of the live objects in a
1571   // bitmap off to the side.
1572   void doConcurrentMark();
1573 
1574   bool isMarkedPrev(oop obj) const;
1575   bool isMarkedNext(oop obj) const;
1576 
1577   // Determine if an object is dead, given the object and also
1578   // the region to which the object belongs. An object is dead
1579   // iff a) it was not allocated since the last mark and b) it
1580   // is not marked.
1581 
1582   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1583     return
1584       !hr->obj_allocated_since_prev_marking(obj) &&
1585       !isMarkedPrev(obj);
1586   }
1587 
1588   // This function returns true when an object has been
1589   // around since the previous marking and hasn't yet
1590   // been marked during this marking.
1591 
1592   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1593     return
1594       !hr->obj_allocated_since_next_marking(obj) &&
1595       !isMarkedNext(obj);
1596   }
1597 
1598   // Determine if an object is dead, given only the object itself.
1599   // This will find the region to which the object belongs and
1600   // then call the region version of the same function.
1601 
1602   // Added if it is NULL it isn't dead.
1603 
1604   bool is_obj_dead(const oop obj) const {
1605     const HeapRegion* hr = heap_region_containing(obj);
1606     if (hr == NULL) {
1607       if (obj == NULL) return false;
1608       else return true;
1609     }
1610     else return is_obj_dead(obj, hr);
1611   }
1612 
1613   bool is_obj_ill(const oop obj) const {
1614     const HeapRegion* hr = heap_region_containing(obj);
1615     if (hr == NULL) {
1616       if (obj == NULL) return false;
1617       else return true;
1618     }
1619     else return is_obj_ill(obj, hr);
1620   }
1621 
1622   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1623   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1624   bool is_marked(oop obj, VerifyOption vo);
1625   const char* top_at_mark_start_str(VerifyOption vo);
1626 
1627   ConcurrentMark* concurrent_mark() const { return _cm; }
1628 
1629   // Refinement
1630 
1631   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1632 
1633   // The dirty cards region list is used to record a subset of regions
1634   // whose cards need clearing. The list if populated during the
1635   // remembered set scanning and drained during the card table
1636   // cleanup. Although the methods are reentrant, population/draining
1637   // phases must not overlap. For synchronization purposes the last
1638   // element on the list points to itself.
1639   HeapRegion* _dirty_cards_region_list;
1640   void push_dirty_cards_region(HeapRegion* hr);
1641   HeapRegion* pop_dirty_cards_region();
1642 
1643   // Optimized nmethod scanning support routines
1644 
1645   // Register the given nmethod with the G1 heap.
1646   virtual void register_nmethod(nmethod* nm);
1647 
1648   // Unregister the given nmethod from the G1 heap.
1649   virtual void unregister_nmethod(nmethod* nm);
1650 
1651   // Migrate the nmethods in the code root lists of the regions
1652   // in the collection set to regions in to-space. In the event
1653   // of an evacuation failure, nmethods that reference objects
1654   // that were not successfully evacuated are not migrated.
1655   void migrate_strong_code_roots();
1656 
1657   // During an initial mark pause, mark all the code roots that
1658   // point into regions *not* in the collection set.
1659   void mark_strong_code_roots(uint worker_id);
1660 
1661   // Rebuild the strong code root lists for each region
1662   // after a full GC.
1663   void rebuild_strong_code_roots();
1664 
1665   // Delete entries for dead interned string and clean up unreferenced symbols
1666   // in symbol table, possibly in parallel.
1667   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1668 
1669   // Verification
1670 
1671   // The following is just to alert the verification code
1672   // that a full collection has occurred and that the
1673   // remembered sets are no longer up to date.
1674   bool _full_collection;
1675   void set_full_collection() { _full_collection = true;}
1676   void clear_full_collection() {_full_collection = false;}
1677   bool full_collection() {return _full_collection;}
1678 
1679   // Perform any cleanup actions necessary before allowing a verification.
1680   virtual void prepare_for_verify();
1681 
1682   // Perform verification.
1683 
1684   // vo == UsePrevMarking  -> use "prev" marking information,
1685   // vo == UseNextMarking -> use "next" marking information
1686   // vo == UseMarkWord    -> use the mark word in the object header
1687   //
1688   // NOTE: Only the "prev" marking information is guaranteed to be
1689   // consistent most of the time, so most calls to this should use
1690   // vo == UsePrevMarking.
1691   // Currently, there is only one case where this is called with
1692   // vo == UseNextMarking, which is to verify the "next" marking
1693   // information at the end of remark.
1694   // Currently there is only one place where this is called with
1695   // vo == UseMarkWord, which is to verify the marking during a
1696   // full GC.
1697   void verify(bool silent, VerifyOption vo);
1698 
1699   // Override; it uses the "prev" marking information
1700   virtual void verify(bool silent);
1701 
1702   // The methods below are here for convenience and dispatch the
1703   // appropriate method depending on value of the given VerifyOption
1704   // parameter. The values for that parameter, and their meanings,
1705   // are the same as those above.
1706 
1707   bool is_obj_dead_cond(const oop obj,
1708                         const HeapRegion* hr,
1709                         const VerifyOption vo) const {
1710     switch (vo) {
1711     case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
1712     case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
1713     case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
1714     default:                            ShouldNotReachHere();
1715     }
1716     return false; // keep some compilers happy
1717   }
1718 
1719   bool is_obj_dead_cond(const oop obj,
1720                         const VerifyOption vo) const {
1721     switch (vo) {
1722     case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
1723     case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
1724     case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
1725     default:                            ShouldNotReachHere();
1726     }
1727     return false; // keep some compilers happy
1728   }
1729 
1730   // Printing
1731 
1732   virtual void print_on(outputStream* st) const;
1733   virtual void print_extended_on(outputStream* st) const;
1734   virtual void print_on_error(outputStream* st) const;
1735 
1736   virtual void print_gc_threads_on(outputStream* st) const;
1737   virtual void gc_threads_do(ThreadClosure* tc) const;
1738 
1739   // Override
1740   void print_tracing_info() const;
1741 
1742   // The following two methods are helpful for debugging RSet issues.
1743   void print_cset_rsets() PRODUCT_RETURN;
1744   void print_all_rsets() PRODUCT_RETURN;
1745 
1746 public:
1747   void stop_conc_gc_threads();
1748 
1749   size_t pending_card_num();
1750   size_t cards_scanned();
1751 
1752 protected:
1753   size_t _max_heap_capacity;
1754 };
1755 
1756 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1757 private:
1758   bool        _retired;
1759 
1760 public:
1761   G1ParGCAllocBuffer(size_t gclab_word_size);
1762 
1763   void set_buf(HeapWord* buf) {
1764     ParGCAllocBuffer::set_buf(buf);
1765     _retired = false;
1766   }
1767 
1768   void retire(bool end_of_gc, bool retain) {
1769     if (_retired)
1770       return;
1771     ParGCAllocBuffer::retire(end_of_gc, retain);
1772     _retired = true;
1773   }
1774 
1775   bool is_retired() {
1776     return _retired;
1777   }
1778 };
1779 
1780 class G1ParGCAllocBufferContainer {
1781 protected:
1782   static int const _priority_max = 2;
1783   G1ParGCAllocBuffer* _priority_buffer[_priority_max];
1784 
1785 public:
1786   G1ParGCAllocBufferContainer(size_t gclab_word_size) {
1787     for (int pr = 0; pr < _priority_max; ++pr) {
1788       _priority_buffer[pr] = new G1ParGCAllocBuffer(gclab_word_size);
1789     }
1790   }
1791 
1792   ~G1ParGCAllocBufferContainer() {
1793     for (int pr = 0; pr < _priority_max; ++pr) {
1794       assert(_priority_buffer[pr]->is_retired(), "alloc buffers should all retire at this point.");
1795       delete _priority_buffer[pr];
1796     }
1797   }
1798 
1799   HeapWord* allocate(size_t word_sz) {
1800     HeapWord* obj;
1801     for (int pr = 0; pr < _priority_max; ++pr) {
1802       obj = _priority_buffer[pr]->allocate(word_sz);
1803       if (obj != NULL) return obj;
1804     }
1805     return obj;
1806   }
1807 
1808   bool contains(void* addr) {
1809     for (int pr = 0; pr < _priority_max; ++pr) {
1810       if (_priority_buffer[pr]->contains(addr)) return true;
1811     }
1812     return false;
1813   }
1814 
1815   void undo_allocation(HeapWord* obj, size_t word_sz) {
1816     bool finish_undo;
1817     for (int pr = 0; pr < _priority_max; ++pr) {
1818       if (_priority_buffer[pr]->contains(obj)) {
1819         _priority_buffer[pr]->undo_allocation(obj, word_sz);
1820         finish_undo = true;
1821       }
1822     }
1823     if (!finish_undo) ShouldNotReachHere();
1824   }
1825 
1826   size_t words_remaining() {
1827     size_t result = 0;
1828     for (int pr = 0; pr < _priority_max; ++pr) {
1829       result += _priority_buffer[pr]->words_remaining();
1830     }
1831     return result;
1832   }
1833 
1834   size_t words_remaining_in_retired_buffer() {
1835     G1ParGCAllocBuffer* retired = _priority_buffer[0];
1836     return retired->words_remaining();
1837   }
1838 
1839   void flush_stats_and_retire(PLABStats* stats, bool end_of_gc, bool retain) {
1840     for (int pr = 0; pr < _priority_max; ++pr) {
1841       _priority_buffer[pr]->flush_stats_and_retire(stats, end_of_gc, retain);
1842     }
1843   }
1844 
1845   void update(bool end_of_gc, bool retain, HeapWord* buf, size_t word_sz) {
1846     G1ParGCAllocBuffer* retired_and_set = _priority_buffer[0];
1847     retired_and_set->retire(end_of_gc, retain);
1848     retired_and_set->set_buf(buf);
1849     retired_and_set->set_word_size(word_sz);
1850     adjust_priority_order();
1851   }
1852 
1853 private:
1854   void adjust_priority_order() {
1855     G1ParGCAllocBuffer* retired_and_set = _priority_buffer[0];
1856 
1857     int last = _priority_max - 1;
1858     for (int pr = 0; pr < last; ++pr) {
1859       _priority_buffer[pr] = _priority_buffer[pr + 1];
1860     }
1861     _priority_buffer[last] = retired_and_set;
1862   }
1863 };
1864 
1865 class G1ParScanThreadState : public StackObj {
1866 protected:
1867   G1CollectedHeap* _g1h;
1868   RefToScanQueue*  _refs;
1869   DirtyCardQueue   _dcq;
1870   G1SATBCardTableModRefBS* _ct_bs;
1871   G1RemSet* _g1_rem;
1872 
1873   G1ParGCAllocBufferContainer  _surviving_alloc_buffer;
1874   G1ParGCAllocBufferContainer  _tenured_alloc_buffer;
1875   G1ParGCAllocBufferContainer* _alloc_buffers[GCAllocPurposeCount];
1876   ageTable            _age_table;
1877 
1878   G1ParScanClosure    _scanner;
1879 
1880   size_t           _alloc_buffer_waste;
1881   size_t           _undo_waste;
1882 
1883   OopsInHeapRegionClosure*      _evac_failure_cl;
1884   G1ParScanHeapEvacClosure*     _evac_cl;
1885   G1ParScanPartialArrayClosure* _partial_scan_cl;
1886 
1887   int  _hash_seed;
1888   uint _queue_num;
1889 
1890   size_t _term_attempts;
1891 
1892   double _start;
1893   double _start_strong_roots;
1894   double _strong_roots_time;
1895   double _start_term;
1896   double _term_time;
1897 
1898   // Map from young-age-index (0 == not young, 1 is youngest) to
1899   // surviving words. base is what we get back from the malloc call
1900   size_t* _surviving_young_words_base;
1901   // this points into the array, as we use the first few entries for padding
1902   size_t* _surviving_young_words;
1903 
1904 #define PADDING_ELEM_NUM (DEFAULT_CACHE_LINE_SIZE / sizeof(size_t))
1905 
1906   void   add_to_alloc_buffer_waste(size_t waste) { _alloc_buffer_waste += waste; }
1907 
1908   void   add_to_undo_waste(size_t waste)         { _undo_waste += waste; }
1909 
1910   DirtyCardQueue& dirty_card_queue()             { return _dcq;  }
1911   G1SATBCardTableModRefBS* ctbs()                { return _ct_bs; }
1912 
1913   template <class T> void immediate_rs_update(HeapRegion* from, T* p, int tid) {
1914     if (!from->is_survivor()) {
1915       _g1_rem->par_write_ref(from, p, tid);
1916     }
1917   }
1918 
1919   template <class T> void deferred_rs_update(HeapRegion* from, T* p, int tid) {
1920     // If the new value of the field points to the same region or
1921     // is the to-space, we don't need to include it in the Rset updates.
1922     if (!from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && !from->is_survivor()) {
1923       size_t card_index = ctbs()->index_for(p);
1924       // If the card hasn't been added to the buffer, do it.
1925       if (ctbs()->mark_card_deferred(card_index)) {
1926         dirty_card_queue().enqueue((jbyte*)ctbs()->byte_for_index(card_index));
1927       }
1928     }
1929   }
1930 
1931 public:
1932   G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num, ReferenceProcessor* rp);
1933 
1934   ~G1ParScanThreadState() {
1935     FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base, mtGC);
1936   }
1937 
1938   RefToScanQueue*   refs()            { return _refs;             }
1939   ageTable*         age_table()       { return &_age_table;       }
1940 
1941   G1ParGCAllocBufferContainer* alloc_buffer(GCAllocPurpose purpose) {
1942     return _alloc_buffers[purpose];
1943   }
1944 
1945   size_t alloc_buffer_waste() const              { return _alloc_buffer_waste; }
1946   size_t undo_waste() const                      { return _undo_waste; }
1947 
1948 #ifdef ASSERT
1949   bool verify_ref(narrowOop* ref) const;
1950   bool verify_ref(oop* ref) const;
1951   bool verify_task(StarTask ref) const;
1952 #endif // ASSERT
1953 
1954   template <class T> void push_on_queue(T* ref) {
1955     assert(verify_ref(ref), "sanity");
1956     refs()->push(ref);
1957   }
1958 
1959   template <class T> void update_rs(HeapRegion* from, T* p, int tid) {
1960     if (G1DeferredRSUpdate) {
1961       deferred_rs_update(from, p, tid);
1962     } else {
1963       immediate_rs_update(from, p, tid);
1964     }
1965   }
1966 
1967   HeapWord* allocate_slow(GCAllocPurpose purpose, size_t word_sz) {
1968     HeapWord* obj = NULL;
1969     size_t gclab_word_size = _g1h->desired_plab_sz(purpose);
1970     if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) {
1971       G1ParGCAllocBufferContainer* alloc_buf = alloc_buffer(purpose);
1972 
1973       HeapWord* buf = _g1h->par_allocate_during_gc(purpose, gclab_word_size);
1974       if (buf == NULL) return NULL; // Let caller handle allocation failure.
1975 
1976       add_to_alloc_buffer_waste(alloc_buf->words_remaining_in_retired_buffer());
1977       alloc_buf->update(false /* end_of_gc */, false /* retain */, buf, gclab_word_size);
1978 
1979       obj = alloc_buf->allocate(word_sz);
1980       assert(obj != NULL, "buffer was definitely big enough...");
1981     } else {
1982       obj = _g1h->par_allocate_during_gc(purpose, word_sz);
1983     }
1984     return obj;
1985   }
1986 
1987   HeapWord* allocate(GCAllocPurpose purpose, size_t word_sz) {
1988     HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz);
1989     if (obj != NULL) return obj;
1990     return allocate_slow(purpose, word_sz);
1991   }
1992 
1993   void undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) {
1994     if (alloc_buffer(purpose)->contains(obj)) {
1995       assert(alloc_buffer(purpose)->contains(obj + word_sz - 1),
1996              "should contain whole object");
1997       alloc_buffer(purpose)->undo_allocation(obj, word_sz);
1998     } else {
1999       CollectedHeap::fill_with_object(obj, word_sz);
2000       add_to_undo_waste(word_sz);
2001     }
2002   }
2003 
2004   void set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_cl) {
2005     _evac_failure_cl = evac_failure_cl;
2006   }
2007   OopsInHeapRegionClosure* evac_failure_closure() {
2008     return _evac_failure_cl;
2009   }
2010 
2011   void set_evac_closure(G1ParScanHeapEvacClosure* evac_cl) {
2012     _evac_cl = evac_cl;
2013   }
2014 
2015   void set_partial_scan_closure(G1ParScanPartialArrayClosure* partial_scan_cl) {
2016     _partial_scan_cl = partial_scan_cl;
2017   }
2018 
2019   int* hash_seed() { return &_hash_seed; }
2020   uint queue_num() { return _queue_num; }
2021 
2022   size_t term_attempts() const  { return _term_attempts; }
2023   void note_term_attempt() { _term_attempts++; }
2024 
2025   void start_strong_roots() {
2026     _start_strong_roots = os::elapsedTime();
2027   }
2028   void end_strong_roots() {
2029     _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
2030   }
2031   double strong_roots_time() const { return _strong_roots_time; }
2032 
2033   void start_term_time() {
2034     note_term_attempt();
2035     _start_term = os::elapsedTime();
2036   }
2037   void end_term_time() {
2038     _term_time += (os::elapsedTime() - _start_term);
2039   }
2040   double term_time() const { return _term_time; }
2041 
2042   double elapsed_time() const {
2043     return os::elapsedTime() - _start;
2044   }
2045 
2046   static void
2047     print_termination_stats_hdr(outputStream* const st = gclog_or_tty);
2048   void
2049     print_termination_stats(int i, outputStream* const st = gclog_or_tty) const;
2050 
2051   size_t* surviving_young_words() {
2052     // We add on to hide entry 0 which accumulates surviving words for
2053     // age -1 regions (i.e. non-young ones)
2054     return _surviving_young_words;
2055   }
2056 
2057   void retire_alloc_buffers() {
2058     for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
2059       size_t waste = _alloc_buffers[ap]->words_remaining();
2060       add_to_alloc_buffer_waste(waste);
2061       _alloc_buffers[ap]->flush_stats_and_retire(_g1h->stats_for_purpose((GCAllocPurpose)ap),
2062                                                  true /* end_of_gc */,
2063                                                  false /* retain */);
2064     }
2065   }
2066 
2067   oop copy_to_survivor_space(oop const obj);
2068 
2069   template <class T> void deal_with_reference(T* ref_to_scan) {
2070     if (has_partial_array_mask(ref_to_scan)) {
2071       _partial_scan_cl->do_oop_nv(ref_to_scan);
2072     } else {
2073       // Note: we can use "raw" versions of "region_containing" because
2074       // "obj_to_scan" is definitely in the heap, and is not in a
2075       // humongous region.
2076       HeapRegion* r = _g1h->heap_region_containing_raw(ref_to_scan);
2077       _evac_cl->set_region(r);
2078       _evac_cl->do_oop_nv(ref_to_scan);
2079     }
2080   }
2081 
2082   void deal_with_reference(StarTask ref) {
2083     assert(verify_task(ref), "sanity");
2084     if (ref.is_narrow()) {
2085       deal_with_reference((narrowOop*)ref);
2086     } else {
2087       deal_with_reference((oop*)ref);
2088     }
2089   }
2090 
2091   void trim_queue();
2092 };
2093 
2094 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
--- EOF ---