src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

Mon, 17 Sep 2012 10:33:13 +0200

author
brutisso
date
Mon, 17 Sep 2012 10:33:13 +0200
changeset 4063
9646b7ff4d14
parent 4037
da91efe96a93
child 4065
8fbf05030e24
permissions
-rw-r--r--

7198130: G1: PrintReferenceGC output comes out of order
Summary: Move the first part of the GC logging, including timestamp, to the start of the GC
Reviewed-by: johnc, jwilhelm

     1 /*
     2  * Copyright (c) 2001, 2012, 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  */
    25 #include "precompiled.hpp"
    26 #include "code/icBuffer.hpp"
    27 #include "gc_implementation/g1/bufferingOopClosure.hpp"
    28 #include "gc_implementation/g1/concurrentG1Refine.hpp"
    29 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
    30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
    31 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
    32 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
    33 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
    34 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
    35 #include "gc_implementation/g1/g1EvacFailure.hpp"
    36 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
    37 #include "gc_implementation/g1/g1Log.hpp"
    38 #include "gc_implementation/g1/g1MarkSweep.hpp"
    39 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
    40 #include "gc_implementation/g1/g1RemSet.inline.hpp"
    41 #include "gc_implementation/g1/heapRegion.inline.hpp"
    42 #include "gc_implementation/g1/heapRegionRemSet.hpp"
    43 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
    44 #include "gc_implementation/g1/vm_operations_g1.hpp"
    45 #include "gc_implementation/shared/isGCActiveMark.hpp"
    46 #include "memory/gcLocker.inline.hpp"
    47 #include "memory/genOopClosures.inline.hpp"
    48 #include "memory/generationSpec.hpp"
    49 #include "memory/referenceProcessor.hpp"
    50 #include "oops/oop.inline.hpp"
    51 #include "oops/oop.pcgc.inline.hpp"
    52 #include "runtime/aprofiler.hpp"
    53 #include "runtime/vmThread.hpp"
    55 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
    57 // turn it on so that the contents of the young list (scan-only /
    58 // to-be-collected) are printed at "strategic" points before / during
    59 // / after the collection --- this is useful for debugging
    60 #define YOUNG_LIST_VERBOSE 0
    61 // CURRENT STATUS
    62 // This file is under construction.  Search for "FIXME".
    64 // INVARIANTS/NOTES
    65 //
    66 // All allocation activity covered by the G1CollectedHeap interface is
    67 // serialized by acquiring the HeapLock.  This happens in mem_allocate
    68 // and allocate_new_tlab, which are the "entry" points to the
    69 // allocation code from the rest of the JVM.  (Note that this does not
    70 // apply to TLAB allocation, which is not part of this interface: it
    71 // is done by clients of this interface.)
    73 // Notes on implementation of parallelism in different tasks.
    74 //
    75 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
    76 // The number of GC workers is passed to heap_region_par_iterate_chunked().
    77 // It does use run_task() which sets _n_workers in the task.
    78 // G1ParTask executes g1_process_strong_roots() ->
    79 // SharedHeap::process_strong_roots() which calls eventuall to
    80 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
    81 // SequentialSubTasksDone.  SharedHeap::process_strong_roots() also
    82 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
    83 //
    85 // Local to this file.
    87 class RefineCardTableEntryClosure: public CardTableEntryClosure {
    88   SuspendibleThreadSet* _sts;
    89   G1RemSet* _g1rs;
    90   ConcurrentG1Refine* _cg1r;
    91   bool _concurrent;
    92 public:
    93   RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
    94                               G1RemSet* g1rs,
    95                               ConcurrentG1Refine* cg1r) :
    96     _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
    97   {}
    98   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
    99     bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
   100     // This path is executed by the concurrent refine or mutator threads,
   101     // concurrently, and so we do not care if card_ptr contains references
   102     // that point into the collection set.
   103     assert(!oops_into_cset, "should be");
   105     if (_concurrent && _sts->should_yield()) {
   106       // Caller will actually yield.
   107       return false;
   108     }
   109     // Otherwise, we finished successfully; return true.
   110     return true;
   111   }
   112   void set_concurrent(bool b) { _concurrent = b; }
   113 };
   116 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
   117   int _calls;
   118   G1CollectedHeap* _g1h;
   119   CardTableModRefBS* _ctbs;
   120   int _histo[256];
   121 public:
   122   ClearLoggedCardTableEntryClosure() :
   123     _calls(0)
   124   {
   125     _g1h = G1CollectedHeap::heap();
   126     _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
   127     for (int i = 0; i < 256; i++) _histo[i] = 0;
   128   }
   129   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
   130     if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
   131       _calls++;
   132       unsigned char* ujb = (unsigned char*)card_ptr;
   133       int ind = (int)(*ujb);
   134       _histo[ind]++;
   135       *card_ptr = -1;
   136     }
   137     return true;
   138   }
   139   int calls() { return _calls; }
   140   void print_histo() {
   141     gclog_or_tty->print_cr("Card table value histogram:");
   142     for (int i = 0; i < 256; i++) {
   143       if (_histo[i] != 0) {
   144         gclog_or_tty->print_cr("  %d: %d", i, _histo[i]);
   145       }
   146     }
   147   }
   148 };
   150 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
   151   int _calls;
   152   G1CollectedHeap* _g1h;
   153   CardTableModRefBS* _ctbs;
   154 public:
   155   RedirtyLoggedCardTableEntryClosure() :
   156     _calls(0)
   157   {
   158     _g1h = G1CollectedHeap::heap();
   159     _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
   160   }
   161   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
   162     if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
   163       _calls++;
   164       *card_ptr = 0;
   165     }
   166     return true;
   167   }
   168   int calls() { return _calls; }
   169 };
   171 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
   172 public:
   173   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
   174     *card_ptr = CardTableModRefBS::dirty_card_val();
   175     return true;
   176   }
   177 };
   179 YoungList::YoungList(G1CollectedHeap* g1h) :
   180     _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
   181     _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
   182   guarantee(check_list_empty(false), "just making sure...");
   183 }
   185 void YoungList::push_region(HeapRegion *hr) {
   186   assert(!hr->is_young(), "should not already be young");
   187   assert(hr->get_next_young_region() == NULL, "cause it should!");
   189   hr->set_next_young_region(_head);
   190   _head = hr;
   192   _g1h->g1_policy()->set_region_eden(hr, (int) _length);
   193   ++_length;
   194 }
   196 void YoungList::add_survivor_region(HeapRegion* hr) {
   197   assert(hr->is_survivor(), "should be flagged as survivor region");
   198   assert(hr->get_next_young_region() == NULL, "cause it should!");
   200   hr->set_next_young_region(_survivor_head);
   201   if (_survivor_head == NULL) {
   202     _survivor_tail = hr;
   203   }
   204   _survivor_head = hr;
   205   ++_survivor_length;
   206 }
   208 void YoungList::empty_list(HeapRegion* list) {
   209   while (list != NULL) {
   210     HeapRegion* next = list->get_next_young_region();
   211     list->set_next_young_region(NULL);
   212     list->uninstall_surv_rate_group();
   213     list->set_not_young();
   214     list = next;
   215   }
   216 }
   218 void YoungList::empty_list() {
   219   assert(check_list_well_formed(), "young list should be well formed");
   221   empty_list(_head);
   222   _head = NULL;
   223   _length = 0;
   225   empty_list(_survivor_head);
   226   _survivor_head = NULL;
   227   _survivor_tail = NULL;
   228   _survivor_length = 0;
   230   _last_sampled_rs_lengths = 0;
   232   assert(check_list_empty(false), "just making sure...");
   233 }
   235 bool YoungList::check_list_well_formed() {
   236   bool ret = true;
   238   uint length = 0;
   239   HeapRegion* curr = _head;
   240   HeapRegion* last = NULL;
   241   while (curr != NULL) {
   242     if (!curr->is_young()) {
   243       gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
   244                              "incorrectly tagged (y: %d, surv: %d)",
   245                              curr->bottom(), curr->end(),
   246                              curr->is_young(), curr->is_survivor());
   247       ret = false;
   248     }
   249     ++length;
   250     last = curr;
   251     curr = curr->get_next_young_region();
   252   }
   253   ret = ret && (length == _length);
   255   if (!ret) {
   256     gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
   257     gclog_or_tty->print_cr("###   list has %u entries, _length is %u",
   258                            length, _length);
   259   }
   261   return ret;
   262 }
   264 bool YoungList::check_list_empty(bool check_sample) {
   265   bool ret = true;
   267   if (_length != 0) {
   268     gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
   269                   _length);
   270     ret = false;
   271   }
   272   if (check_sample && _last_sampled_rs_lengths != 0) {
   273     gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
   274     ret = false;
   275   }
   276   if (_head != NULL) {
   277     gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
   278     ret = false;
   279   }
   280   if (!ret) {
   281     gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
   282   }
   284   return ret;
   285 }
   287 void
   288 YoungList::rs_length_sampling_init() {
   289   _sampled_rs_lengths = 0;
   290   _curr               = _head;
   291 }
   293 bool
   294 YoungList::rs_length_sampling_more() {
   295   return _curr != NULL;
   296 }
   298 void
   299 YoungList::rs_length_sampling_next() {
   300   assert( _curr != NULL, "invariant" );
   301   size_t rs_length = _curr->rem_set()->occupied();
   303   _sampled_rs_lengths += rs_length;
   305   // The current region may not yet have been added to the
   306   // incremental collection set (it gets added when it is
   307   // retired as the current allocation region).
   308   if (_curr->in_collection_set()) {
   309     // Update the collection set policy information for this region
   310     _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
   311   }
   313   _curr = _curr->get_next_young_region();
   314   if (_curr == NULL) {
   315     _last_sampled_rs_lengths = _sampled_rs_lengths;
   316     // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
   317   }
   318 }
   320 void
   321 YoungList::reset_auxilary_lists() {
   322   guarantee( is_empty(), "young list should be empty" );
   323   assert(check_list_well_formed(), "young list should be well formed");
   325   // Add survivor regions to SurvRateGroup.
   326   _g1h->g1_policy()->note_start_adding_survivor_regions();
   327   _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
   329   int young_index_in_cset = 0;
   330   for (HeapRegion* curr = _survivor_head;
   331        curr != NULL;
   332        curr = curr->get_next_young_region()) {
   333     _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
   335     // The region is a non-empty survivor so let's add it to
   336     // the incremental collection set for the next evacuation
   337     // pause.
   338     _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
   339     young_index_in_cset += 1;
   340   }
   341   assert((uint) young_index_in_cset == _survivor_length, "post-condition");
   342   _g1h->g1_policy()->note_stop_adding_survivor_regions();
   344   _head   = _survivor_head;
   345   _length = _survivor_length;
   346   if (_survivor_head != NULL) {
   347     assert(_survivor_tail != NULL, "cause it shouldn't be");
   348     assert(_survivor_length > 0, "invariant");
   349     _survivor_tail->set_next_young_region(NULL);
   350   }
   352   // Don't clear the survivor list handles until the start of
   353   // the next evacuation pause - we need it in order to re-tag
   354   // the survivor regions from this evacuation pause as 'young'
   355   // at the start of the next.
   357   _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
   359   assert(check_list_well_formed(), "young list should be well formed");
   360 }
   362 void YoungList::print() {
   363   HeapRegion* lists[] = {_head,   _survivor_head};
   364   const char* names[] = {"YOUNG", "SURVIVOR"};
   366   for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
   367     gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
   368     HeapRegion *curr = lists[list];
   369     if (curr == NULL)
   370       gclog_or_tty->print_cr("  empty");
   371     while (curr != NULL) {
   372       gclog_or_tty->print_cr("  "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
   373                              HR_FORMAT_PARAMS(curr),
   374                              curr->prev_top_at_mark_start(),
   375                              curr->next_top_at_mark_start(),
   376                              curr->age_in_surv_rate_group_cond());
   377       curr = curr->get_next_young_region();
   378     }
   379   }
   381   gclog_or_tty->print_cr("");
   382 }
   384 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
   385 {
   386   // Claim the right to put the region on the dirty cards region list
   387   // by installing a self pointer.
   388   HeapRegion* next = hr->get_next_dirty_cards_region();
   389   if (next == NULL) {
   390     HeapRegion* res = (HeapRegion*)
   391       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
   392                           NULL);
   393     if (res == NULL) {
   394       HeapRegion* head;
   395       do {
   396         // Put the region to the dirty cards region list.
   397         head = _dirty_cards_region_list;
   398         next = (HeapRegion*)
   399           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
   400         if (next == head) {
   401           assert(hr->get_next_dirty_cards_region() == hr,
   402                  "hr->get_next_dirty_cards_region() != hr");
   403           if (next == NULL) {
   404             // The last region in the list points to itself.
   405             hr->set_next_dirty_cards_region(hr);
   406           } else {
   407             hr->set_next_dirty_cards_region(next);
   408           }
   409         }
   410       } while (next != head);
   411     }
   412   }
   413 }
   415 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
   416 {
   417   HeapRegion* head;
   418   HeapRegion* hr;
   419   do {
   420     head = _dirty_cards_region_list;
   421     if (head == NULL) {
   422       return NULL;
   423     }
   424     HeapRegion* new_head = head->get_next_dirty_cards_region();
   425     if (head == new_head) {
   426       // The last region.
   427       new_head = NULL;
   428     }
   429     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
   430                                           head);
   431   } while (hr != head);
   432   assert(hr != NULL, "invariant");
   433   hr->set_next_dirty_cards_region(NULL);
   434   return hr;
   435 }
   437 void G1CollectedHeap::stop_conc_gc_threads() {
   438   _cg1r->stop();
   439   _cmThread->stop();
   440 }
   442 #ifdef ASSERT
   443 // A region is added to the collection set as it is retired
   444 // so an address p can point to a region which will be in the
   445 // collection set but has not yet been retired.  This method
   446 // therefore is only accurate during a GC pause after all
   447 // regions have been retired.  It is used for debugging
   448 // to check if an nmethod has references to objects that can
   449 // be move during a partial collection.  Though it can be
   450 // inaccurate, it is sufficient for G1 because the conservative
   451 // implementation of is_scavengable() for G1 will indicate that
   452 // all nmethods must be scanned during a partial collection.
   453 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
   454   HeapRegion* hr = heap_region_containing(p);
   455   return hr != NULL && hr->in_collection_set();
   456 }
   457 #endif
   459 // Returns true if the reference points to an object that
   460 // can move in an incremental collecction.
   461 bool G1CollectedHeap::is_scavengable(const void* p) {
   462   G1CollectedHeap* g1h = G1CollectedHeap::heap();
   463   G1CollectorPolicy* g1p = g1h->g1_policy();
   464   HeapRegion* hr = heap_region_containing(p);
   465   if (hr == NULL) {
   466      // null
   467      assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p));
   468      return false;
   469   } else {
   470     return !hr->isHumongous();
   471   }
   472 }
   474 void G1CollectedHeap::check_ct_logs_at_safepoint() {
   475   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
   476   CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
   478   // Count the dirty cards at the start.
   479   CountNonCleanMemRegionClosure count1(this);
   480   ct_bs->mod_card_iterate(&count1);
   481   int orig_count = count1.n();
   483   // First clear the logged cards.
   484   ClearLoggedCardTableEntryClosure clear;
   485   dcqs.set_closure(&clear);
   486   dcqs.apply_closure_to_all_completed_buffers();
   487   dcqs.iterate_closure_all_threads(false);
   488   clear.print_histo();
   490   // Now ensure that there's no dirty cards.
   491   CountNonCleanMemRegionClosure count2(this);
   492   ct_bs->mod_card_iterate(&count2);
   493   if (count2.n() != 0) {
   494     gclog_or_tty->print_cr("Card table has %d entries; %d originally",
   495                            count2.n(), orig_count);
   496   }
   497   guarantee(count2.n() == 0, "Card table should be clean.");
   499   RedirtyLoggedCardTableEntryClosure redirty;
   500   JavaThread::dirty_card_queue_set().set_closure(&redirty);
   501   dcqs.apply_closure_to_all_completed_buffers();
   502   dcqs.iterate_closure_all_threads(false);
   503   gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
   504                          clear.calls(), orig_count);
   505   guarantee(redirty.calls() == clear.calls(),
   506             "Or else mechanism is broken.");
   508   CountNonCleanMemRegionClosure count3(this);
   509   ct_bs->mod_card_iterate(&count3);
   510   if (count3.n() != orig_count) {
   511     gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
   512                            orig_count, count3.n());
   513     guarantee(count3.n() >= orig_count, "Should have restored them all.");
   514   }
   516   JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
   517 }
   519 // Private class members.
   521 G1CollectedHeap* G1CollectedHeap::_g1h;
   523 // Private methods.
   525 HeapRegion*
   526 G1CollectedHeap::new_region_try_secondary_free_list() {
   527   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
   528   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
   529     if (!_secondary_free_list.is_empty()) {
   530       if (G1ConcRegionFreeingVerbose) {
   531         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
   532                                "secondary_free_list has %u entries",
   533                                _secondary_free_list.length());
   534       }
   535       // It looks as if there are free regions available on the
   536       // secondary_free_list. Let's move them to the free_list and try
   537       // again to allocate from it.
   538       append_secondary_free_list();
   540       assert(!_free_list.is_empty(), "if the secondary_free_list was not "
   541              "empty we should have moved at least one entry to the free_list");
   542       HeapRegion* res = _free_list.remove_head();
   543       if (G1ConcRegionFreeingVerbose) {
   544         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
   545                                "allocated "HR_FORMAT" from secondary_free_list",
   546                                HR_FORMAT_PARAMS(res));
   547       }
   548       return res;
   549     }
   551     // Wait here until we get notifed either when (a) there are no
   552     // more free regions coming or (b) some regions have been moved on
   553     // the secondary_free_list.
   554     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
   555   }
   557   if (G1ConcRegionFreeingVerbose) {
   558     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
   559                            "could not allocate from secondary_free_list");
   560   }
   561   return NULL;
   562 }
   564 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
   565   assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
   566          "the only time we use this to allocate a humongous region is "
   567          "when we are allocating a single humongous region");
   569   HeapRegion* res;
   570   if (G1StressConcRegionFreeing) {
   571     if (!_secondary_free_list.is_empty()) {
   572       if (G1ConcRegionFreeingVerbose) {
   573         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
   574                                "forced to look at the secondary_free_list");
   575       }
   576       res = new_region_try_secondary_free_list();
   577       if (res != NULL) {
   578         return res;
   579       }
   580     }
   581   }
   582   res = _free_list.remove_head_or_null();
   583   if (res == NULL) {
   584     if (G1ConcRegionFreeingVerbose) {
   585       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
   586                              "res == NULL, trying the secondary_free_list");
   587     }
   588     res = new_region_try_secondary_free_list();
   589   }
   590   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
   591     // Currently, only attempts to allocate GC alloc regions set
   592     // do_expand to true. So, we should only reach here during a
   593     // safepoint. If this assumption changes we might have to
   594     // reconsider the use of _expand_heap_after_alloc_failure.
   595     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
   597     ergo_verbose1(ErgoHeapSizing,
   598                   "attempt heap expansion",
   599                   ergo_format_reason("region allocation request failed")
   600                   ergo_format_byte("allocation request"),
   601                   word_size * HeapWordSize);
   602     if (expand(word_size * HeapWordSize)) {
   603       // Given that expand() succeeded in expanding the heap, and we
   604       // always expand the heap by an amount aligned to the heap
   605       // region size, the free list should in theory not be empty. So
   606       // it would probably be OK to use remove_head(). But the extra
   607       // check for NULL is unlikely to be a performance issue here (we
   608       // just expanded the heap!) so let's just be conservative and
   609       // use remove_head_or_null().
   610       res = _free_list.remove_head_or_null();
   611     } else {
   612       _expand_heap_after_alloc_failure = false;
   613     }
   614   }
   615   return res;
   616 }
   618 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
   619                                                         size_t word_size) {
   620   assert(isHumongous(word_size), "word_size should be humongous");
   621   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
   623   uint first = G1_NULL_HRS_INDEX;
   624   if (num_regions == 1) {
   625     // Only one region to allocate, no need to go through the slower
   626     // path. The caller will attempt the expasion if this fails, so
   627     // let's not try to expand here too.
   628     HeapRegion* hr = new_region(word_size, false /* do_expand */);
   629     if (hr != NULL) {
   630       first = hr->hrs_index();
   631     } else {
   632       first = G1_NULL_HRS_INDEX;
   633     }
   634   } else {
   635     // We can't allocate humongous regions while cleanupComplete() is
   636     // running, since some of the regions we find to be empty might not
   637     // yet be added to the free list and it is not straightforward to
   638     // know which list they are on so that we can remove them. Note
   639     // that we only need to do this if we need to allocate more than
   640     // one region to satisfy the current humongous allocation
   641     // request. If we are only allocating one region we use the common
   642     // region allocation code (see above).
   643     wait_while_free_regions_coming();
   644     append_secondary_free_list_if_not_empty_with_lock();
   646     if (free_regions() >= num_regions) {
   647       first = _hrs.find_contiguous(num_regions);
   648       if (first != G1_NULL_HRS_INDEX) {
   649         for (uint i = first; i < first + num_regions; ++i) {
   650           HeapRegion* hr = region_at(i);
   651           assert(hr->is_empty(), "sanity");
   652           assert(is_on_master_free_list(hr), "sanity");
   653           hr->set_pending_removal(true);
   654         }
   655         _free_list.remove_all_pending(num_regions);
   656       }
   657     }
   658   }
   659   return first;
   660 }
   662 HeapWord*
   663 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
   664                                                            uint num_regions,
   665                                                            size_t word_size) {
   666   assert(first != G1_NULL_HRS_INDEX, "pre-condition");
   667   assert(isHumongous(word_size), "word_size should be humongous");
   668   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
   670   // Index of last region in the series + 1.
   671   uint last = first + num_regions;
   673   // We need to initialize the region(s) we just discovered. This is
   674   // a bit tricky given that it can happen concurrently with
   675   // refinement threads refining cards on these regions and
   676   // potentially wanting to refine the BOT as they are scanning
   677   // those cards (this can happen shortly after a cleanup; see CR
   678   // 6991377). So we have to set up the region(s) carefully and in
   679   // a specific order.
   681   // The word size sum of all the regions we will allocate.
   682   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
   683   assert(word_size <= word_size_sum, "sanity");
   685   // This will be the "starts humongous" region.
   686   HeapRegion* first_hr = region_at(first);
   687   // The header of the new object will be placed at the bottom of
   688   // the first region.
   689   HeapWord* new_obj = first_hr->bottom();
   690   // This will be the new end of the first region in the series that
   691   // should also match the end of the last region in the seriers.
   692   HeapWord* new_end = new_obj + word_size_sum;
   693   // This will be the new top of the first region that will reflect
   694   // this allocation.
   695   HeapWord* new_top = new_obj + word_size;
   697   // First, we need to zero the header of the space that we will be
   698   // allocating. When we update top further down, some refinement
   699   // threads might try to scan the region. By zeroing the header we
   700   // ensure that any thread that will try to scan the region will
   701   // come across the zero klass word and bail out.
   702   //
   703   // NOTE: It would not have been correct to have used
   704   // CollectedHeap::fill_with_object() and make the space look like
   705   // an int array. The thread that is doing the allocation will
   706   // later update the object header to a potentially different array
   707   // type and, for a very short period of time, the klass and length
   708   // fields will be inconsistent. This could cause a refinement
   709   // thread to calculate the object size incorrectly.
   710   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
   712   // We will set up the first region as "starts humongous". This
   713   // will also update the BOT covering all the regions to reflect
   714   // that there is a single object that starts at the bottom of the
   715   // first region.
   716   first_hr->set_startsHumongous(new_top, new_end);
   718   // Then, if there are any, we will set up the "continues
   719   // humongous" regions.
   720   HeapRegion* hr = NULL;
   721   for (uint i = first + 1; i < last; ++i) {
   722     hr = region_at(i);
   723     hr->set_continuesHumongous(first_hr);
   724   }
   725   // If we have "continues humongous" regions (hr != NULL), then the
   726   // end of the last one should match new_end.
   727   assert(hr == NULL || hr->end() == new_end, "sanity");
   729   // Up to this point no concurrent thread would have been able to
   730   // do any scanning on any region in this series. All the top
   731   // fields still point to bottom, so the intersection between
   732   // [bottom,top] and [card_start,card_end] will be empty. Before we
   733   // update the top fields, we'll do a storestore to make sure that
   734   // no thread sees the update to top before the zeroing of the
   735   // object header and the BOT initialization.
   736   OrderAccess::storestore();
   738   // Now that the BOT and the object header have been initialized,
   739   // we can update top of the "starts humongous" region.
   740   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
   741          "new_top should be in this region");
   742   first_hr->set_top(new_top);
   743   if (_hr_printer.is_active()) {
   744     HeapWord* bottom = first_hr->bottom();
   745     HeapWord* end = first_hr->orig_end();
   746     if ((first + 1) == last) {
   747       // the series has a single humongous region
   748       _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
   749     } else {
   750       // the series has more than one humongous regions
   751       _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
   752     }
   753   }
   755   // Now, we will update the top fields of the "continues humongous"
   756   // regions. The reason we need to do this is that, otherwise,
   757   // these regions would look empty and this will confuse parts of
   758   // G1. For example, the code that looks for a consecutive number
   759   // of empty regions will consider them empty and try to
   760   // re-allocate them. We can extend is_empty() to also include
   761   // !continuesHumongous(), but it is easier to just update the top
   762   // fields here. The way we set top for all regions (i.e., top ==
   763   // end for all regions but the last one, top == new_top for the
   764   // last one) is actually used when we will free up the humongous
   765   // region in free_humongous_region().
   766   hr = NULL;
   767   for (uint i = first + 1; i < last; ++i) {
   768     hr = region_at(i);
   769     if ((i + 1) == last) {
   770       // last continues humongous region
   771       assert(hr->bottom() < new_top && new_top <= hr->end(),
   772              "new_top should fall on this region");
   773       hr->set_top(new_top);
   774       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
   775     } else {
   776       // not last one
   777       assert(new_top > hr->end(), "new_top should be above this region");
   778       hr->set_top(hr->end());
   779       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
   780     }
   781   }
   782   // If we have continues humongous regions (hr != NULL), then the
   783   // end of the last one should match new_end and its top should
   784   // match new_top.
   785   assert(hr == NULL ||
   786          (hr->end() == new_end && hr->top() == new_top), "sanity");
   788   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
   789   _summary_bytes_used += first_hr->used();
   790   _humongous_set.add(first_hr);
   792   return new_obj;
   793 }
   795 // If could fit into free regions w/o expansion, try.
   796 // Otherwise, if can expand, do so.
   797 // Otherwise, if using ex regions might help, try with ex given back.
   798 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
   799   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
   801   verify_region_sets_optional();
   803   size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
   804   uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
   805   uint x_num = expansion_regions();
   806   uint fs = _hrs.free_suffix();
   807   uint first = humongous_obj_allocate_find_first(num_regions, word_size);
   808   if (first == G1_NULL_HRS_INDEX) {
   809     // The only thing we can do now is attempt expansion.
   810     if (fs + x_num >= num_regions) {
   811       // If the number of regions we're trying to allocate for this
   812       // object is at most the number of regions in the free suffix,
   813       // then the call to humongous_obj_allocate_find_first() above
   814       // should have succeeded and we wouldn't be here.
   815       //
   816       // We should only be trying to expand when the free suffix is
   817       // not sufficient for the object _and_ we have some expansion
   818       // room available.
   819       assert(num_regions > fs, "earlier allocation should have succeeded");
   821       ergo_verbose1(ErgoHeapSizing,
   822                     "attempt heap expansion",
   823                     ergo_format_reason("humongous allocation request failed")
   824                     ergo_format_byte("allocation request"),
   825                     word_size * HeapWordSize);
   826       if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
   827         // Even though the heap was expanded, it might not have
   828         // reached the desired size. So, we cannot assume that the
   829         // allocation will succeed.
   830         first = humongous_obj_allocate_find_first(num_regions, word_size);
   831       }
   832     }
   833   }
   835   HeapWord* result = NULL;
   836   if (first != G1_NULL_HRS_INDEX) {
   837     result =
   838       humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
   839     assert(result != NULL, "it should always return a valid result");
   841     // A successful humongous object allocation changes the used space
   842     // information of the old generation so we need to recalculate the
   843     // sizes and update the jstat counters here.
   844     g1mm()->update_sizes();
   845   }
   847   verify_region_sets_optional();
   849   return result;
   850 }
   852 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
   853   assert_heap_not_locked_and_not_at_safepoint();
   854   assert(!isHumongous(word_size), "we do not allow humongous TLABs");
   856   unsigned int dummy_gc_count_before;
   857   return attempt_allocation(word_size, &dummy_gc_count_before);
   858 }
   860 HeapWord*
   861 G1CollectedHeap::mem_allocate(size_t word_size,
   862                               bool*  gc_overhead_limit_was_exceeded) {
   863   assert_heap_not_locked_and_not_at_safepoint();
   865   // Loop until the allocation is satisified, or unsatisfied after GC.
   866   for (int try_count = 1; /* we'll return */; try_count += 1) {
   867     unsigned int gc_count_before;
   869     HeapWord* result = NULL;
   870     if (!isHumongous(word_size)) {
   871       result = attempt_allocation(word_size, &gc_count_before);
   872     } else {
   873       result = attempt_allocation_humongous(word_size, &gc_count_before);
   874     }
   875     if (result != NULL) {
   876       return result;
   877     }
   879     // Create the garbage collection operation...
   880     VM_G1CollectForAllocation op(gc_count_before, word_size);
   881     // ...and get the VM thread to execute it.
   882     VMThread::execute(&op);
   884     if (op.prologue_succeeded() && op.pause_succeeded()) {
   885       // If the operation was successful we'll return the result even
   886       // if it is NULL. If the allocation attempt failed immediately
   887       // after a Full GC, it's unlikely we'll be able to allocate now.
   888       HeapWord* result = op.result();
   889       if (result != NULL && !isHumongous(word_size)) {
   890         // Allocations that take place on VM operations do not do any
   891         // card dirtying and we have to do it here. We only have to do
   892         // this for non-humongous allocations, though.
   893         dirty_young_block(result, word_size);
   894       }
   895       return result;
   896     } else {
   897       assert(op.result() == NULL,
   898              "the result should be NULL if the VM op did not succeed");
   899     }
   901     // Give a warning if we seem to be looping forever.
   902     if ((QueuedAllocationWarningCount > 0) &&
   903         (try_count % QueuedAllocationWarningCount == 0)) {
   904       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
   905     }
   906   }
   908   ShouldNotReachHere();
   909   return NULL;
   910 }
   912 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
   913                                            unsigned int *gc_count_before_ret) {
   914   // Make sure you read the note in attempt_allocation_humongous().
   916   assert_heap_not_locked_and_not_at_safepoint();
   917   assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
   918          "be called for humongous allocation requests");
   920   // We should only get here after the first-level allocation attempt
   921   // (attempt_allocation()) failed to allocate.
   923   // We will loop until a) we manage to successfully perform the
   924   // allocation or b) we successfully schedule a collection which
   925   // fails to perform the allocation. b) is the only case when we'll
   926   // return NULL.
   927   HeapWord* result = NULL;
   928   for (int try_count = 1; /* we'll return */; try_count += 1) {
   929     bool should_try_gc;
   930     unsigned int gc_count_before;
   932     {
   933       MutexLockerEx x(Heap_lock);
   935       result = _mutator_alloc_region.attempt_allocation_locked(word_size,
   936                                                       false /* bot_updates */);
   937       if (result != NULL) {
   938         return result;
   939       }
   941       // If we reach here, attempt_allocation_locked() above failed to
   942       // allocate a new region. So the mutator alloc region should be NULL.
   943       assert(_mutator_alloc_region.get() == NULL, "only way to get here");
   945       if (GC_locker::is_active_and_needs_gc()) {
   946         if (g1_policy()->can_expand_young_list()) {
   947           // No need for an ergo verbose message here,
   948           // can_expand_young_list() does this when it returns true.
   949           result = _mutator_alloc_region.attempt_allocation_force(word_size,
   950                                                       false /* bot_updates */);
   951           if (result != NULL) {
   952             return result;
   953           }
   954         }
   955         should_try_gc = false;
   956       } else {
   957         // The GCLocker may not be active but the GCLocker initiated
   958         // GC may not yet have been performed (GCLocker::needs_gc()
   959         // returns true). In this case we do not try this GC and
   960         // wait until the GCLocker initiated GC is performed, and
   961         // then retry the allocation.
   962         if (GC_locker::needs_gc()) {
   963           should_try_gc = false;
   964         } else {
   965           // Read the GC count while still holding the Heap_lock.
   966           gc_count_before = total_collections();
   967           should_try_gc = true;
   968         }
   969       }
   970     }
   972     if (should_try_gc) {
   973       bool succeeded;
   974       result = do_collection_pause(word_size, gc_count_before, &succeeded);
   975       if (result != NULL) {
   976         assert(succeeded, "only way to get back a non-NULL result");
   977         return result;
   978       }
   980       if (succeeded) {
   981         // If we get here we successfully scheduled a collection which
   982         // failed to allocate. No point in trying to allocate
   983         // further. We'll just return NULL.
   984         MutexLockerEx x(Heap_lock);
   985         *gc_count_before_ret = total_collections();
   986         return NULL;
   987       }
   988     } else {
   989       // The GCLocker is either active or the GCLocker initiated
   990       // GC has not yet been performed. Stall until it is and
   991       // then retry the allocation.
   992       GC_locker::stall_until_clear();
   993     }
   995     // We can reach here if we were unsuccessul in scheduling a
   996     // collection (because another thread beat us to it) or if we were
   997     // stalled due to the GC locker. In either can we should retry the
   998     // allocation attempt in case another thread successfully
   999     // performed a collection and reclaimed enough space. We do the
  1000     // first attempt (without holding the Heap_lock) here and the
  1001     // follow-on attempt will be at the start of the next loop
  1002     // iteration (after taking the Heap_lock).
  1003     result = _mutator_alloc_region.attempt_allocation(word_size,
  1004                                                       false /* bot_updates */);
  1005     if (result != NULL) {
  1006       return result;
  1009     // Give a warning if we seem to be looping forever.
  1010     if ((QueuedAllocationWarningCount > 0) &&
  1011         (try_count % QueuedAllocationWarningCount == 0)) {
  1012       warning("G1CollectedHeap::attempt_allocation_slow() "
  1013               "retries %d times", try_count);
  1017   ShouldNotReachHere();
  1018   return NULL;
  1021 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
  1022                                           unsigned int * gc_count_before_ret) {
  1023   // The structure of this method has a lot of similarities to
  1024   // attempt_allocation_slow(). The reason these two were not merged
  1025   // into a single one is that such a method would require several "if
  1026   // allocation is not humongous do this, otherwise do that"
  1027   // conditional paths which would obscure its flow. In fact, an early
  1028   // version of this code did use a unified method which was harder to
  1029   // follow and, as a result, it had subtle bugs that were hard to
  1030   // track down. So keeping these two methods separate allows each to
  1031   // be more readable. It will be good to keep these two in sync as
  1032   // much as possible.
  1034   assert_heap_not_locked_and_not_at_safepoint();
  1035   assert(isHumongous(word_size), "attempt_allocation_humongous() "
  1036          "should only be called for humongous allocations");
  1038   // Humongous objects can exhaust the heap quickly, so we should check if we
  1039   // need to start a marking cycle at each humongous object allocation. We do
  1040   // the check before we do the actual allocation. The reason for doing it
  1041   // before the allocation is that we avoid having to keep track of the newly
  1042   // allocated memory while we do a GC.
  1043   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
  1044                                            word_size)) {
  1045     collect(GCCause::_g1_humongous_allocation);
  1048   // We will loop until a) we manage to successfully perform the
  1049   // allocation or b) we successfully schedule a collection which
  1050   // fails to perform the allocation. b) is the only case when we'll
  1051   // return NULL.
  1052   HeapWord* result = NULL;
  1053   for (int try_count = 1; /* we'll return */; try_count += 1) {
  1054     bool should_try_gc;
  1055     unsigned int gc_count_before;
  1058       MutexLockerEx x(Heap_lock);
  1060       // Given that humongous objects are not allocated in young
  1061       // regions, we'll first try to do the allocation without doing a
  1062       // collection hoping that there's enough space in the heap.
  1063       result = humongous_obj_allocate(word_size);
  1064       if (result != NULL) {
  1065         return result;
  1068       if (GC_locker::is_active_and_needs_gc()) {
  1069         should_try_gc = false;
  1070       } else {
  1071          // The GCLocker may not be active but the GCLocker initiated
  1072         // GC may not yet have been performed (GCLocker::needs_gc()
  1073         // returns true). In this case we do not try this GC and
  1074         // wait until the GCLocker initiated GC is performed, and
  1075         // then retry the allocation.
  1076         if (GC_locker::needs_gc()) {
  1077           should_try_gc = false;
  1078         } else {
  1079           // Read the GC count while still holding the Heap_lock.
  1080           gc_count_before = total_collections();
  1081           should_try_gc = true;
  1086     if (should_try_gc) {
  1087       // If we failed to allocate the humongous object, we should try to
  1088       // do a collection pause (if we're allowed) in case it reclaims
  1089       // enough space for the allocation to succeed after the pause.
  1091       bool succeeded;
  1092       result = do_collection_pause(word_size, gc_count_before, &succeeded);
  1093       if (result != NULL) {
  1094         assert(succeeded, "only way to get back a non-NULL result");
  1095         return result;
  1098       if (succeeded) {
  1099         // If we get here we successfully scheduled a collection which
  1100         // failed to allocate. No point in trying to allocate
  1101         // further. We'll just return NULL.
  1102         MutexLockerEx x(Heap_lock);
  1103         *gc_count_before_ret = total_collections();
  1104         return NULL;
  1106     } else {
  1107       // The GCLocker is either active or the GCLocker initiated
  1108       // GC has not yet been performed. Stall until it is and
  1109       // then retry the allocation.
  1110       GC_locker::stall_until_clear();
  1113     // We can reach here if we were unsuccessul in scheduling a
  1114     // collection (because another thread beat us to it) or if we were
  1115     // stalled due to the GC locker. In either can we should retry the
  1116     // allocation attempt in case another thread successfully
  1117     // performed a collection and reclaimed enough space.  Give a
  1118     // warning if we seem to be looping forever.
  1120     if ((QueuedAllocationWarningCount > 0) &&
  1121         (try_count % QueuedAllocationWarningCount == 0)) {
  1122       warning("G1CollectedHeap::attempt_allocation_humongous() "
  1123               "retries %d times", try_count);
  1127   ShouldNotReachHere();
  1128   return NULL;
  1131 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
  1132                                        bool expect_null_mutator_alloc_region) {
  1133   assert_at_safepoint(true /* should_be_vm_thread */);
  1134   assert(_mutator_alloc_region.get() == NULL ||
  1135                                              !expect_null_mutator_alloc_region,
  1136          "the current alloc region was unexpectedly found to be non-NULL");
  1138   if (!isHumongous(word_size)) {
  1139     return _mutator_alloc_region.attempt_allocation_locked(word_size,
  1140                                                       false /* bot_updates */);
  1141   } else {
  1142     HeapWord* result = humongous_obj_allocate(word_size);
  1143     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
  1144       g1_policy()->set_initiate_conc_mark_if_possible();
  1146     return result;
  1149   ShouldNotReachHere();
  1152 class PostMCRemSetClearClosure: public HeapRegionClosure {
  1153   G1CollectedHeap* _g1h;
  1154   ModRefBarrierSet* _mr_bs;
  1155 public:
  1156   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
  1157     _g1h(g1h), _mr_bs(mr_bs) { }
  1158   bool doHeapRegion(HeapRegion* r) {
  1159     if (r->continuesHumongous()) {
  1160       return false;
  1162     _g1h->reset_gc_time_stamps(r);
  1163     HeapRegionRemSet* hrrs = r->rem_set();
  1164     if (hrrs != NULL) hrrs->clear();
  1165     // You might think here that we could clear just the cards
  1166     // corresponding to the used region.  But no: if we leave a dirty card
  1167     // in a region we might allocate into, then it would prevent that card
  1168     // from being enqueued, and cause it to be missed.
  1169     // Re: the performance cost: we shouldn't be doing full GC anyway!
  1170     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
  1171     return false;
  1173 };
  1175 void G1CollectedHeap::clear_rsets_post_compaction() {
  1176   PostMCRemSetClearClosure rs_clear(this, mr_bs());
  1177   heap_region_iterate(&rs_clear);
  1180 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
  1181   G1CollectedHeap*   _g1h;
  1182   UpdateRSOopClosure _cl;
  1183   int                _worker_i;
  1184 public:
  1185   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
  1186     _cl(g1->g1_rem_set(), worker_i),
  1187     _worker_i(worker_i),
  1188     _g1h(g1)
  1189   { }
  1191   bool doHeapRegion(HeapRegion* r) {
  1192     if (!r->continuesHumongous()) {
  1193       _cl.set_from(r);
  1194       r->oop_iterate(&_cl);
  1196     return false;
  1198 };
  1200 class ParRebuildRSTask: public AbstractGangTask {
  1201   G1CollectedHeap* _g1;
  1202 public:
  1203   ParRebuildRSTask(G1CollectedHeap* g1)
  1204     : AbstractGangTask("ParRebuildRSTask"),
  1205       _g1(g1)
  1206   { }
  1208   void work(uint worker_id) {
  1209     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
  1210     _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
  1211                                           _g1->workers()->active_workers(),
  1212                                          HeapRegion::RebuildRSClaimValue);
  1214 };
  1216 class PostCompactionPrinterClosure: public HeapRegionClosure {
  1217 private:
  1218   G1HRPrinter* _hr_printer;
  1219 public:
  1220   bool doHeapRegion(HeapRegion* hr) {
  1221     assert(!hr->is_young(), "not expecting to find young regions");
  1222     // We only generate output for non-empty regions.
  1223     if (!hr->is_empty()) {
  1224       if (!hr->isHumongous()) {
  1225         _hr_printer->post_compaction(hr, G1HRPrinter::Old);
  1226       } else if (hr->startsHumongous()) {
  1227         if (hr->region_num() == 1) {
  1228           // single humongous region
  1229           _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
  1230         } else {
  1231           _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
  1233       } else {
  1234         assert(hr->continuesHumongous(), "only way to get here");
  1235         _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
  1238     return false;
  1241   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
  1242     : _hr_printer(hr_printer) { }
  1243 };
  1245 void G1CollectedHeap::print_hrs_post_compaction() {
  1246   PostCompactionPrinterClosure cl(hr_printer());
  1247   heap_region_iterate(&cl);
  1250 double G1CollectedHeap::verify(bool guard, const char* msg) {
  1251   double verify_time_ms = 0.0;
  1253   if (guard && total_collections() >= VerifyGCStartAt) {
  1254     double verify_start = os::elapsedTime();
  1255     HandleMark hm;  // Discard invalid handles created during verification
  1256     gclog_or_tty->print(msg);
  1257     prepare_for_verify();
  1258     Universe::verify(false /* silent */, VerifyOption_G1UsePrevMarking);
  1259     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
  1262   return verify_time_ms;
  1265 void G1CollectedHeap::verify_before_gc() {
  1266   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
  1267   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
  1270 void G1CollectedHeap::verify_after_gc() {
  1271   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
  1272   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
  1275 bool G1CollectedHeap::do_collection(bool explicit_gc,
  1276                                     bool clear_all_soft_refs,
  1277                                     size_t word_size) {
  1278   assert_at_safepoint(true /* should_be_vm_thread */);
  1280   if (GC_locker::check_active_before_gc()) {
  1281     return false;
  1284   SvcGCMarker sgcm(SvcGCMarker::FULL);
  1285   ResourceMark rm;
  1287   print_heap_before_gc();
  1289   size_t metadata_prev_used = MetaspaceAux::used_in_bytes();
  1291   HRSPhaseSetter x(HRSPhaseFullGC);
  1292   verify_region_sets_optional();
  1294   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
  1295                            collector_policy()->should_clear_all_soft_refs();
  1297   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
  1300     IsGCActiveMark x;
  1302     // Timing
  1303     assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
  1304     gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
  1305     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
  1307     TraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, gclog_or_tty);
  1308     TraceCollectorStats tcs(g1mm()->full_collection_counters());
  1309     TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
  1311     double start = os::elapsedTime();
  1312     g1_policy()->record_full_collection_start();
  1314     // Note: When we have a more flexible GC logging framework that
  1315     // allows us to add optional attributes to a GC log record we
  1316     // could consider timing and reporting how long we wait in the
  1317     // following two methods.
  1318     wait_while_free_regions_coming();
  1319     // If we start the compaction before the CM threads finish
  1320     // scanning the root regions we might trip them over as we'll
  1321     // be moving objects / updating references. So let's wait until
  1322     // they are done. By telling them to abort, they should complete
  1323     // early.
  1324     _cm->root_regions()->abort();
  1325     _cm->root_regions()->wait_until_scan_finished();
  1326     append_secondary_free_list_if_not_empty_with_lock();
  1328     gc_prologue(true);
  1329     increment_total_collections(true /* full gc */);
  1330     increment_old_marking_cycles_started();
  1332     size_t g1h_prev_used = used();
  1333     assert(used() == recalculate_used(), "Should be equal");
  1335     verify_before_gc();
  1337     pre_full_gc_dump();
  1339     COMPILER2_PRESENT(DerivedPointerTable::clear());
  1341     // Disable discovery and empty the discovered lists
  1342     // for the CM ref processor.
  1343     ref_processor_cm()->disable_discovery();
  1344     ref_processor_cm()->abandon_partial_discovery();
  1345     ref_processor_cm()->verify_no_references_recorded();
  1347     // Abandon current iterations of concurrent marking and concurrent
  1348     // refinement, if any are in progress. We have to do this before
  1349     // wait_until_scan_finished() below.
  1350     concurrent_mark()->abort();
  1352     // Make sure we'll choose a new allocation region afterwards.
  1353     release_mutator_alloc_region();
  1354     abandon_gc_alloc_regions();
  1355     g1_rem_set()->cleanupHRRS();
  1357     // We should call this after we retire any currently active alloc
  1358     // regions so that all the ALLOC / RETIRE events are generated
  1359     // before the start GC event.
  1360     _hr_printer.start_gc(true /* full */, (size_t) total_collections());
  1362     // We may have added regions to the current incremental collection
  1363     // set between the last GC or pause and now. We need to clear the
  1364     // incremental collection set and then start rebuilding it afresh
  1365     // after this full GC.
  1366     abandon_collection_set(g1_policy()->inc_cset_head());
  1367     g1_policy()->clear_incremental_cset();
  1368     g1_policy()->stop_incremental_cset_building();
  1370     tear_down_region_sets(false /* free_list_only */);
  1371     g1_policy()->set_gcs_are_young(true);
  1373     // See the comments in g1CollectedHeap.hpp and
  1374     // G1CollectedHeap::ref_processing_init() about
  1375     // how reference processing currently works in G1.
  1377     // Temporarily make discovery by the STW ref processor single threaded (non-MT).
  1378     ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
  1380     // Temporarily clear the STW ref processor's _is_alive_non_header field.
  1381     ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
  1383     ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
  1384     ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
  1386     // Do collection work
  1388       HandleMark hm;  // Discard invalid handles created during gc
  1389       G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
  1392     assert(free_regions() == 0, "we should not have added any free regions");
  1393     rebuild_region_sets(false /* free_list_only */);
  1395     // Enqueue any discovered reference objects that have
  1396     // not been removed from the discovered lists.
  1397     ref_processor_stw()->enqueue_discovered_references();
  1399     COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
  1401     MemoryService::track_memory_usage();
  1403     verify_after_gc();
  1405     assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
  1406     ref_processor_stw()->verify_no_references_recorded();
  1408     // Delete metaspaces for unloaded class loaders and clean up loader_data graph
  1409     ClassLoaderDataGraph::purge();
  1411     // Note: since we've just done a full GC, concurrent
  1412     // marking is no longer active. Therefore we need not
  1413     // re-enable reference discovery for the CM ref processor.
  1414     // That will be done at the start of the next marking cycle.
  1415     assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
  1416     ref_processor_cm()->verify_no_references_recorded();
  1418     reset_gc_time_stamp();
  1419     // Since everything potentially moved, we will clear all remembered
  1420     // sets, and clear all cards.  Later we will rebuild remebered
  1421     // sets. We will also reset the GC time stamps of the regions.
  1422     clear_rsets_post_compaction();
  1423     check_gc_time_stamps();
  1425     // Resize the heap if necessary.
  1426     resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
  1428     if (_hr_printer.is_active()) {
  1429       // We should do this after we potentially resize the heap so
  1430       // that all the COMMIT / UNCOMMIT events are generated before
  1431       // the end GC event.
  1433       print_hrs_post_compaction();
  1434       _hr_printer.end_gc(true /* full */, (size_t) total_collections());
  1437     if (_cg1r->use_cache()) {
  1438       _cg1r->clear_and_record_card_counts();
  1439       _cg1r->clear_hot_cache();
  1442     // Rebuild remembered sets of all regions.
  1443     if (G1CollectedHeap::use_parallel_gc_threads()) {
  1444       uint n_workers =
  1445         AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
  1446                                        workers()->active_workers(),
  1447                                        Threads::number_of_non_daemon_threads());
  1448       assert(UseDynamicNumberOfGCThreads ||
  1449              n_workers == workers()->total_workers(),
  1450              "If not dynamic should be using all the  workers");
  1451       workers()->set_active_workers(n_workers);
  1452       // Set parallel threads in the heap (_n_par_threads) only
  1453       // before a parallel phase and always reset it to 0 after
  1454       // the phase so that the number of parallel threads does
  1455       // no get carried forward to a serial phase where there
  1456       // may be code that is "possibly_parallel".
  1457       set_par_threads(n_workers);
  1459       ParRebuildRSTask rebuild_rs_task(this);
  1460       assert(check_heap_region_claim_values(
  1461              HeapRegion::InitialClaimValue), "sanity check");
  1462       assert(UseDynamicNumberOfGCThreads ||
  1463              workers()->active_workers() == workers()->total_workers(),
  1464         "Unless dynamic should use total workers");
  1465       // Use the most recent number of  active workers
  1466       assert(workers()->active_workers() > 0,
  1467         "Active workers not properly set");
  1468       set_par_threads(workers()->active_workers());
  1469       workers()->run_task(&rebuild_rs_task);
  1470       set_par_threads(0);
  1471       assert(check_heap_region_claim_values(
  1472              HeapRegion::RebuildRSClaimValue), "sanity check");
  1473       reset_heap_region_claim_values();
  1474     } else {
  1475       RebuildRSOutOfRegionClosure rebuild_rs(this);
  1476       heap_region_iterate(&rebuild_rs);
  1479     if (G1Log::fine()) {
  1480       print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
  1483     if (true) { // FIXME
  1484       MetaspaceGC::compute_new_size();
  1487     // Start a new incremental collection set for the next pause
  1488     assert(g1_policy()->collection_set() == NULL, "must be");
  1489     g1_policy()->start_incremental_cset_building();
  1491     // Clear the _cset_fast_test bitmap in anticipation of adding
  1492     // regions to the incremental collection set for the next
  1493     // evacuation pause.
  1494     clear_cset_fast_test();
  1496     init_mutator_alloc_region();
  1498     double end = os::elapsedTime();
  1499     g1_policy()->record_full_collection_end();
  1501 #ifdef TRACESPINNING
  1502     ParallelTaskTerminator::print_termination_counts();
  1503 #endif
  1505     gc_epilogue(true);
  1507     // Discard all rset updates
  1508     JavaThread::dirty_card_queue_set().abandon_logs();
  1509     assert(!G1DeferredRSUpdate
  1510            || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
  1512     _young_list->reset_sampled_info();
  1513     // At this point there should be no regions in the
  1514     // entire heap tagged as young.
  1515     assert( check_young_list_empty(true /* check_heap */),
  1516       "young list should be empty at this point");
  1518     // Update the number of full collections that have been completed.
  1519     increment_old_marking_cycles_completed(false /* concurrent */);
  1521     _hrs.verify_optional();
  1522     verify_region_sets_optional();
  1524     print_heap_after_gc();
  1526     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
  1527     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
  1528     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
  1529     // before any GC notifications are raised.
  1530     g1mm()->update_sizes();
  1533   post_full_gc_dump();
  1535   return true;
  1538 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
  1539   // do_collection() will return whether it succeeded in performing
  1540   // the GC. Currently, there is no facility on the
  1541   // do_full_collection() API to notify the caller than the collection
  1542   // did not succeed (e.g., because it was locked out by the GC
  1543   // locker). So, right now, we'll ignore the return value.
  1544   bool dummy = do_collection(true,                /* explicit_gc */
  1545                              clear_all_soft_refs,
  1546                              0                    /* word_size */);
  1549 // This code is mostly copied from TenuredGeneration.
  1550 void
  1551 G1CollectedHeap::
  1552 resize_if_necessary_after_full_collection(size_t word_size) {
  1553   assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
  1555   // Include the current allocation, if any, and bytes that will be
  1556   // pre-allocated to support collections, as "used".
  1557   const size_t used_after_gc = used();
  1558   const size_t capacity_after_gc = capacity();
  1559   const size_t free_after_gc = capacity_after_gc - used_after_gc;
  1561   // This is enforced in arguments.cpp.
  1562   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
  1563          "otherwise the code below doesn't make sense");
  1565   // We don't have floating point command-line arguments
  1566   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
  1567   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
  1568   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
  1569   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
  1571   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
  1572   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
  1574   // We have to be careful here as these two calculations can overflow
  1575   // 32-bit size_t's.
  1576   double used_after_gc_d = (double) used_after_gc;
  1577   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
  1578   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
  1580   // Let's make sure that they are both under the max heap size, which
  1581   // by default will make them fit into a size_t.
  1582   double desired_capacity_upper_bound = (double) max_heap_size;
  1583   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
  1584                                     desired_capacity_upper_bound);
  1585   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
  1586                                     desired_capacity_upper_bound);
  1588   // We can now safely turn them into size_t's.
  1589   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
  1590   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
  1592   // This assert only makes sense here, before we adjust them
  1593   // with respect to the min and max heap size.
  1594   assert(minimum_desired_capacity <= maximum_desired_capacity,
  1595          err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
  1596                  "maximum_desired_capacity = "SIZE_FORMAT,
  1597                  minimum_desired_capacity, maximum_desired_capacity));
  1599   // Should not be greater than the heap max size. No need to adjust
  1600   // it with respect to the heap min size as it's a lower bound (i.e.,
  1601   // we'll try to make the capacity larger than it, not smaller).
  1602   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
  1603   // Should not be less than the heap min size. No need to adjust it
  1604   // with respect to the heap max size as it's an upper bound (i.e.,
  1605   // we'll try to make the capacity smaller than it, not greater).
  1606   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
  1608   if (capacity_after_gc < minimum_desired_capacity) {
  1609     // Don't expand unless it's significant
  1610     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
  1611     ergo_verbose4(ErgoHeapSizing,
  1612                   "attempt heap expansion",
  1613                   ergo_format_reason("capacity lower than "
  1614                                      "min desired capacity after Full GC")
  1615                   ergo_format_byte("capacity")
  1616                   ergo_format_byte("occupancy")
  1617                   ergo_format_byte_perc("min desired capacity"),
  1618                   capacity_after_gc, used_after_gc,
  1619                   minimum_desired_capacity, (double) MinHeapFreeRatio);
  1620     expand(expand_bytes);
  1622     // No expansion, now see if we want to shrink
  1623   } else if (capacity_after_gc > maximum_desired_capacity) {
  1624     // Capacity too large, compute shrinking size
  1625     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
  1626     ergo_verbose4(ErgoHeapSizing,
  1627                   "attempt heap shrinking",
  1628                   ergo_format_reason("capacity higher than "
  1629                                      "max desired capacity after Full GC")
  1630                   ergo_format_byte("capacity")
  1631                   ergo_format_byte("occupancy")
  1632                   ergo_format_byte_perc("max desired capacity"),
  1633                   capacity_after_gc, used_after_gc,
  1634                   maximum_desired_capacity, (double) MaxHeapFreeRatio);
  1635     shrink(shrink_bytes);
  1640 HeapWord*
  1641 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
  1642                                            bool* succeeded) {
  1643   assert_at_safepoint(true /* should_be_vm_thread */);
  1645   *succeeded = true;
  1646   // Let's attempt the allocation first.
  1647   HeapWord* result =
  1648     attempt_allocation_at_safepoint(word_size,
  1649                                  false /* expect_null_mutator_alloc_region */);
  1650   if (result != NULL) {
  1651     assert(*succeeded, "sanity");
  1652     return result;
  1655   // In a G1 heap, we're supposed to keep allocation from failing by
  1656   // incremental pauses.  Therefore, at least for now, we'll favor
  1657   // expansion over collection.  (This might change in the future if we can
  1658   // do something smarter than full collection to satisfy a failed alloc.)
  1659   result = expand_and_allocate(word_size);
  1660   if (result != NULL) {
  1661     assert(*succeeded, "sanity");
  1662     return result;
  1665   // Expansion didn't work, we'll try to do a Full GC.
  1666   bool gc_succeeded = do_collection(false, /* explicit_gc */
  1667                                     false, /* clear_all_soft_refs */
  1668                                     word_size);
  1669   if (!gc_succeeded) {
  1670     *succeeded = false;
  1671     return NULL;
  1674   // Retry the allocation
  1675   result = attempt_allocation_at_safepoint(word_size,
  1676                                   true /* expect_null_mutator_alloc_region */);
  1677   if (result != NULL) {
  1678     assert(*succeeded, "sanity");
  1679     return result;
  1682   // Then, try a Full GC that will collect all soft references.
  1683   gc_succeeded = do_collection(false, /* explicit_gc */
  1684                                true,  /* clear_all_soft_refs */
  1685                                word_size);
  1686   if (!gc_succeeded) {
  1687     *succeeded = false;
  1688     return NULL;
  1691   // Retry the allocation once more
  1692   result = attempt_allocation_at_safepoint(word_size,
  1693                                   true /* expect_null_mutator_alloc_region */);
  1694   if (result != NULL) {
  1695     assert(*succeeded, "sanity");
  1696     return result;
  1699   assert(!collector_policy()->should_clear_all_soft_refs(),
  1700          "Flag should have been handled and cleared prior to this point");
  1702   // What else?  We might try synchronous finalization later.  If the total
  1703   // space available is large enough for the allocation, then a more
  1704   // complete compaction phase than we've tried so far might be
  1705   // appropriate.
  1706   assert(*succeeded, "sanity");
  1707   return NULL;
  1710 // Attempting to expand the heap sufficiently
  1711 // to support an allocation of the given "word_size".  If
  1712 // successful, perform the allocation and return the address of the
  1713 // allocated block, or else "NULL".
  1715 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
  1716   assert_at_safepoint(true /* should_be_vm_thread */);
  1718   verify_region_sets_optional();
  1720   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
  1721   ergo_verbose1(ErgoHeapSizing,
  1722                 "attempt heap expansion",
  1723                 ergo_format_reason("allocation request failed")
  1724                 ergo_format_byte("allocation request"),
  1725                 word_size * HeapWordSize);
  1726   if (expand(expand_bytes)) {
  1727     _hrs.verify_optional();
  1728     verify_region_sets_optional();
  1729     return attempt_allocation_at_safepoint(word_size,
  1730                                  false /* expect_null_mutator_alloc_region */);
  1732   return NULL;
  1735 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
  1736                                              HeapWord* new_end) {
  1737   assert(old_end != new_end, "don't call this otherwise");
  1738   assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
  1740   // Update the committed mem region.
  1741   _g1_committed.set_end(new_end);
  1742   // Tell the card table about the update.
  1743   Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
  1744   // Tell the BOT about the update.
  1745   _bot_shared->resize(_g1_committed.word_size());
  1748 bool G1CollectedHeap::expand(size_t expand_bytes) {
  1749   size_t old_mem_size = _g1_storage.committed_size();
  1750   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
  1751   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
  1752                                        HeapRegion::GrainBytes);
  1753   ergo_verbose2(ErgoHeapSizing,
  1754                 "expand the heap",
  1755                 ergo_format_byte("requested expansion amount")
  1756                 ergo_format_byte("attempted expansion amount"),
  1757                 expand_bytes, aligned_expand_bytes);
  1759   // First commit the memory.
  1760   HeapWord* old_end = (HeapWord*) _g1_storage.high();
  1761   bool successful = _g1_storage.expand_by(aligned_expand_bytes);
  1762   if (successful) {
  1763     // Then propagate this update to the necessary data structures.
  1764     HeapWord* new_end = (HeapWord*) _g1_storage.high();
  1765     update_committed_space(old_end, new_end);
  1767     FreeRegionList expansion_list("Local Expansion List");
  1768     MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
  1769     assert(mr.start() == old_end, "post-condition");
  1770     // mr might be a smaller region than what was requested if
  1771     // expand_by() was unable to allocate the HeapRegion instances
  1772     assert(mr.end() <= new_end, "post-condition");
  1774     size_t actual_expand_bytes = mr.byte_size();
  1775     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
  1776     assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
  1777            "post-condition");
  1778     if (actual_expand_bytes < aligned_expand_bytes) {
  1779       // We could not expand _hrs to the desired size. In this case we
  1780       // need to shrink the committed space accordingly.
  1781       assert(mr.end() < new_end, "invariant");
  1783       size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
  1784       // First uncommit the memory.
  1785       _g1_storage.shrink_by(diff_bytes);
  1786       // Then propagate this update to the necessary data structures.
  1787       update_committed_space(new_end, mr.end());
  1789     _free_list.add_as_tail(&expansion_list);
  1791     if (_hr_printer.is_active()) {
  1792       HeapWord* curr = mr.start();
  1793       while (curr < mr.end()) {
  1794         HeapWord* curr_end = curr + HeapRegion::GrainWords;
  1795         _hr_printer.commit(curr, curr_end);
  1796         curr = curr_end;
  1798       assert(curr == mr.end(), "post-condition");
  1800     g1_policy()->record_new_heap_size(n_regions());
  1801   } else {
  1802     ergo_verbose0(ErgoHeapSizing,
  1803                   "did not expand the heap",
  1804                   ergo_format_reason("heap expansion operation failed"));
  1805     // The expansion of the virtual storage space was unsuccessful.
  1806     // Let's see if it was because we ran out of swap.
  1807     if (G1ExitOnExpansionFailure &&
  1808         _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
  1809       // We had head room...
  1810       vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
  1813   return successful;
  1816 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
  1817   size_t old_mem_size = _g1_storage.committed_size();
  1818   size_t aligned_shrink_bytes =
  1819     ReservedSpace::page_align_size_down(shrink_bytes);
  1820   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
  1821                                          HeapRegion::GrainBytes);
  1822   uint num_regions_deleted = 0;
  1823   MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
  1824   HeapWord* old_end = (HeapWord*) _g1_storage.high();
  1825   assert(mr.end() == old_end, "post-condition");
  1827   ergo_verbose3(ErgoHeapSizing,
  1828                 "shrink the heap",
  1829                 ergo_format_byte("requested shrinking amount")
  1830                 ergo_format_byte("aligned shrinking amount")
  1831                 ergo_format_byte("attempted shrinking amount"),
  1832                 shrink_bytes, aligned_shrink_bytes, mr.byte_size());
  1833   if (mr.byte_size() > 0) {
  1834     if (_hr_printer.is_active()) {
  1835       HeapWord* curr = mr.end();
  1836       while (curr > mr.start()) {
  1837         HeapWord* curr_end = curr;
  1838         curr -= HeapRegion::GrainWords;
  1839         _hr_printer.uncommit(curr, curr_end);
  1841       assert(curr == mr.start(), "post-condition");
  1844     _g1_storage.shrink_by(mr.byte_size());
  1845     HeapWord* new_end = (HeapWord*) _g1_storage.high();
  1846     assert(mr.start() == new_end, "post-condition");
  1848     _expansion_regions += num_regions_deleted;
  1849     update_committed_space(old_end, new_end);
  1850     HeapRegionRemSet::shrink_heap(n_regions());
  1851     g1_policy()->record_new_heap_size(n_regions());
  1852   } else {
  1853     ergo_verbose0(ErgoHeapSizing,
  1854                   "did not shrink the heap",
  1855                   ergo_format_reason("heap shrinking operation failed"));
  1859 void G1CollectedHeap::shrink(size_t shrink_bytes) {
  1860   verify_region_sets_optional();
  1862   // We should only reach here at the end of a Full GC which means we
  1863   // should not not be holding to any GC alloc regions. The method
  1864   // below will make sure of that and do any remaining clean up.
  1865   abandon_gc_alloc_regions();
  1867   // Instead of tearing down / rebuilding the free lists here, we
  1868   // could instead use the remove_all_pending() method on free_list to
  1869   // remove only the ones that we need to remove.
  1870   tear_down_region_sets(true /* free_list_only */);
  1871   shrink_helper(shrink_bytes);
  1872   rebuild_region_sets(true /* free_list_only */);
  1874   _hrs.verify_optional();
  1875   verify_region_sets_optional();
  1878 // Public methods.
  1880 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
  1881 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
  1882 #endif // _MSC_VER
  1885 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
  1886   SharedHeap(policy_),
  1887   _g1_policy(policy_),
  1888   _dirty_card_queue_set(false),
  1889   _into_cset_dirty_card_queue_set(false),
  1890   _is_alive_closure_cm(this),
  1891   _is_alive_closure_stw(this),
  1892   _ref_processor_cm(NULL),
  1893   _ref_processor_stw(NULL),
  1894   _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
  1895   _bot_shared(NULL),
  1896   _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
  1897   _evac_failure_scan_stack(NULL) ,
  1898   _mark_in_progress(false),
  1899   _cg1r(NULL), _summary_bytes_used(0),
  1900   _g1mm(NULL),
  1901   _refine_cte_cl(NULL),
  1902   _full_collection(false),
  1903   _free_list("Master Free List"),
  1904   _secondary_free_list("Secondary Free List"),
  1905   _old_set("Old Set"),
  1906   _humongous_set("Master Humongous Set"),
  1907   _free_regions_coming(false),
  1908   _young_list(new YoungList(this)),
  1909   _gc_time_stamp(0),
  1910   _retained_old_gc_alloc_region(NULL),
  1911   _survivor_plab_stats(YoungPLABSize, PLABWeight),
  1912   _old_plab_stats(OldPLABSize, PLABWeight),
  1913   _expand_heap_after_alloc_failure(true),
  1914   _surviving_young_words(NULL),
  1915   _old_marking_cycles_started(0),
  1916   _old_marking_cycles_completed(0),
  1917   _in_cset_fast_test(NULL),
  1918   _in_cset_fast_test_base(NULL),
  1919   _dirty_cards_region_list(NULL),
  1920   _worker_cset_start_region(NULL),
  1921   _worker_cset_start_region_time_stamp(NULL) {
  1922   _g1h = this; // To catch bugs.
  1923   if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
  1924     vm_exit_during_initialization("Failed necessary allocation.");
  1927   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
  1929   int n_queues = MAX2((int)ParallelGCThreads, 1);
  1930   _task_queues = new RefToScanQueueSet(n_queues);
  1932   int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
  1933   assert(n_rem_sets > 0, "Invariant.");
  1935   HeapRegionRemSetIterator** iter_arr =
  1936     NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues, mtGC);
  1937   for (int i = 0; i < n_queues; i++) {
  1938     iter_arr[i] = new HeapRegionRemSetIterator();
  1940   _rem_set_iterator = iter_arr;
  1942   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
  1943   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
  1945   for (int i = 0; i < n_queues; i++) {
  1946     RefToScanQueue* q = new RefToScanQueue();
  1947     q->initialize();
  1948     _task_queues->register_queue(i, q);
  1951   clear_cset_start_regions();
  1953   // Initialize the G1EvacuationFailureALot counters and flags.
  1954   NOT_PRODUCT(reset_evacuation_should_fail();)
  1956   guarantee(_task_queues != NULL, "task_queues allocation failure.");
  1957 #ifdef SPARC
  1958   // Issue a stern warning, but allow use for experimentation and debugging.
  1959   if (VM_Version::is_sun4v() && UseMemSetInBOT) {
  1960     assert(!FLAG_IS_DEFAULT(UseMemSetInBOT), "Error");
  1961     warning("Experimental flag -XX:+UseMemSetInBOT is known to cause instability"
  1962             " on sun4v; please understand that you are using at your own risk!");
  1964 #endif
  1967 jint G1CollectedHeap::initialize() {
  1968   CollectedHeap::pre_initialize();
  1969   os::enable_vtime();
  1971   G1Log::init();
  1973   // Necessary to satisfy locking discipline assertions.
  1975   MutexLocker x(Heap_lock);
  1977   // We have to initialize the printer before committing the heap, as
  1978   // it will be used then.
  1979   _hr_printer.set_active(G1PrintHeapRegions);
  1981   // While there are no constraints in the GC code that HeapWordSize
  1982   // be any particular value, there are multiple other areas in the
  1983   // system which believe this to be true (e.g. oop->object_size in some
  1984   // cases incorrectly returns the size in wordSize units rather than
  1985   // HeapWordSize).
  1986   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
  1988   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
  1989   size_t max_byte_size = collector_policy()->max_heap_byte_size();
  1991   // Ensure that the sizes are properly aligned.
  1992   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
  1993   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
  1995   _cg1r = new ConcurrentG1Refine();
  1997   // Reserve the maximum.
  1999   // When compressed oops are enabled, the preferred heap base
  2000   // is calculated by subtracting the requested size from the
  2001   // 32Gb boundary and using the result as the base address for
  2002   // heap reservation. If the requested size is not aligned to
  2003   // HeapRegion::GrainBytes (i.e. the alignment that is passed
  2004   // into the ReservedHeapSpace constructor) then the actual
  2005   // base of the reserved heap may end up differing from the
  2006   // address that was requested (i.e. the preferred heap base).
  2007   // If this happens then we could end up using a non-optimal
  2008   // compressed oops mode.
  2010   // Since max_byte_size is aligned to the size of a heap region (checked
  2011   // above).
  2012   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
  2014   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
  2015                                                  HeapRegion::GrainBytes);
  2017   // It is important to do this in a way such that concurrent readers can't
  2018   // temporarily think somethings in the heap.  (I've actually seen this
  2019   // happen in asserts: DLD.)
  2020   _reserved.set_word_size(0);
  2021   _reserved.set_start((HeapWord*)heap_rs.base());
  2022   _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
  2024   _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
  2026   // Create the gen rem set (and barrier set) for the entire reserved region.
  2027   _rem_set = collector_policy()->create_rem_set(_reserved, 2);
  2028   set_barrier_set(rem_set()->bs());
  2029   if (barrier_set()->is_a(BarrierSet::ModRef)) {
  2030     _mr_bs = (ModRefBarrierSet*)_barrier_set;
  2031   } else {
  2032     vm_exit_during_initialization("G1 requires a mod ref bs.");
  2033     return JNI_ENOMEM;
  2036   // Also create a G1 rem set.
  2037   if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
  2038     _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
  2039   } else {
  2040     vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
  2041     return JNI_ENOMEM;
  2044   // Carve out the G1 part of the heap.
  2046   ReservedSpace g1_rs   = heap_rs.first_part(max_byte_size);
  2047   _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
  2048                            g1_rs.size()/HeapWordSize);
  2050   _g1_storage.initialize(g1_rs, 0);
  2051   _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
  2052   _hrs.initialize((HeapWord*) _g1_reserved.start(),
  2053                   (HeapWord*) _g1_reserved.end(),
  2054                   _expansion_regions);
  2056   // 6843694 - ensure that the maximum region index can fit
  2057   // in the remembered set structures.
  2058   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
  2059   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
  2061   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
  2062   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
  2063   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
  2064             "too many cards per region");
  2066   HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
  2068   _bot_shared = new G1BlockOffsetSharedArray(_reserved,
  2069                                              heap_word_size(init_byte_size));
  2071   _g1h = this;
  2073    _in_cset_fast_test_length = max_regions();
  2074    _in_cset_fast_test_base =
  2075                    NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
  2077    // We're biasing _in_cset_fast_test to avoid subtracting the
  2078    // beginning of the heap every time we want to index; basically
  2079    // it's the same with what we do with the card table.
  2080    _in_cset_fast_test = _in_cset_fast_test_base -
  2081                ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
  2083    // Clear the _cset_fast_test bitmap in anticipation of adding
  2084    // regions to the incremental collection set for the first
  2085    // evacuation pause.
  2086    clear_cset_fast_test();
  2088   // Create the ConcurrentMark data structure and thread.
  2089   // (Must do this late, so that "max_regions" is defined.)
  2090   _cm       = new ConcurrentMark(heap_rs, max_regions());
  2091   _cmThread = _cm->cmThread();
  2093   // Initialize the from_card cache structure of HeapRegionRemSet.
  2094   HeapRegionRemSet::init_heap(max_regions());
  2096   // Now expand into the initial heap size.
  2097   if (!expand(init_byte_size)) {
  2098     vm_exit_during_initialization("Failed to allocate initial heap.");
  2099     return JNI_ENOMEM;
  2102   // Perform any initialization actions delegated to the policy.
  2103   g1_policy()->init();
  2105   _refine_cte_cl =
  2106     new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
  2107                                     g1_rem_set(),
  2108                                     concurrent_g1_refine());
  2109   JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
  2111   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
  2112                                                SATB_Q_FL_lock,
  2113                                                G1SATBProcessCompletedThreshold,
  2114                                                Shared_SATB_Q_lock);
  2116   JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
  2117                                                 DirtyCardQ_FL_lock,
  2118                                                 concurrent_g1_refine()->yellow_zone(),
  2119                                                 concurrent_g1_refine()->red_zone(),
  2120                                                 Shared_DirtyCardQ_lock);
  2122   if (G1DeferredRSUpdate) {
  2123     dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
  2124                                       DirtyCardQ_FL_lock,
  2125                                       -1, // never trigger processing
  2126                                       -1, // no limit on length
  2127                                       Shared_DirtyCardQ_lock,
  2128                                       &JavaThread::dirty_card_queue_set());
  2131   // Initialize the card queue set used to hold cards containing
  2132   // references into the collection set.
  2133   _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
  2134                                              DirtyCardQ_FL_lock,
  2135                                              -1, // never trigger processing
  2136                                              -1, // no limit on length
  2137                                              Shared_DirtyCardQ_lock,
  2138                                              &JavaThread::dirty_card_queue_set());
  2140   // In case we're keeping closure specialization stats, initialize those
  2141   // counts and that mechanism.
  2142   SpecializationStats::clear();
  2144   // Do later initialization work for concurrent refinement.
  2145   _cg1r->init();
  2147   // Here we allocate the dummy full region that is required by the
  2148   // G1AllocRegion class. If we don't pass an address in the reserved
  2149   // space here, lots of asserts fire.
  2151   HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
  2152                                              _g1_reserved.start());
  2153   // We'll re-use the same region whether the alloc region will
  2154   // require BOT updates or not and, if it doesn't, then a non-young
  2155   // region will complain that it cannot support allocations without
  2156   // BOT updates. So we'll tag the dummy region as young to avoid that.
  2157   dummy_region->set_young();
  2158   // Make sure it's full.
  2159   dummy_region->set_top(dummy_region->end());
  2160   G1AllocRegion::setup(this, dummy_region);
  2162   init_mutator_alloc_region();
  2164   // Do create of the monitoring and management support so that
  2165   // values in the heap have been properly initialized.
  2166   _g1mm = new G1MonitoringSupport(this);
  2168   return JNI_OK;
  2171 void G1CollectedHeap::ref_processing_init() {
  2172   // Reference processing in G1 currently works as follows:
  2173   //
  2174   // * There are two reference processor instances. One is
  2175   //   used to record and process discovered references
  2176   //   during concurrent marking; the other is used to
  2177   //   record and process references during STW pauses
  2178   //   (both full and incremental).
  2179   // * Both ref processors need to 'span' the entire heap as
  2180   //   the regions in the collection set may be dotted around.
  2181   //
  2182   // * For the concurrent marking ref processor:
  2183   //   * Reference discovery is enabled at initial marking.
  2184   //   * Reference discovery is disabled and the discovered
  2185   //     references processed etc during remarking.
  2186   //   * Reference discovery is MT (see below).
  2187   //   * Reference discovery requires a barrier (see below).
  2188   //   * Reference processing may or may not be MT
  2189   //     (depending on the value of ParallelRefProcEnabled
  2190   //     and ParallelGCThreads).
  2191   //   * A full GC disables reference discovery by the CM
  2192   //     ref processor and abandons any entries on it's
  2193   //     discovered lists.
  2194   //
  2195   // * For the STW processor:
  2196   //   * Non MT discovery is enabled at the start of a full GC.
  2197   //   * Processing and enqueueing during a full GC is non-MT.
  2198   //   * During a full GC, references are processed after marking.
  2199   //
  2200   //   * Discovery (may or may not be MT) is enabled at the start
  2201   //     of an incremental evacuation pause.
  2202   //   * References are processed near the end of a STW evacuation pause.
  2203   //   * For both types of GC:
  2204   //     * Discovery is atomic - i.e. not concurrent.
  2205   //     * Reference discovery will not need a barrier.
  2207   SharedHeap::ref_processing_init();
  2208   MemRegion mr = reserved_region();
  2210   // Concurrent Mark ref processor
  2211   _ref_processor_cm =
  2212     new ReferenceProcessor(mr,    // span
  2213                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
  2214                                 // mt processing
  2215                            (int) ParallelGCThreads,
  2216                                 // degree of mt processing
  2217                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
  2218                                 // mt discovery
  2219                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
  2220                                 // degree of mt discovery
  2221                            false,
  2222                                 // Reference discovery is not atomic
  2223                            &_is_alive_closure_cm,
  2224                                 // is alive closure
  2225                                 // (for efficiency/performance)
  2226                            true);
  2227                                 // Setting next fields of discovered
  2228                                 // lists requires a barrier.
  2230   // STW ref processor
  2231   _ref_processor_stw =
  2232     new ReferenceProcessor(mr,    // span
  2233                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
  2234                                 // mt processing
  2235                            MAX2((int)ParallelGCThreads, 1),
  2236                                 // degree of mt processing
  2237                            (ParallelGCThreads > 1),
  2238                                 // mt discovery
  2239                            MAX2((int)ParallelGCThreads, 1),
  2240                                 // degree of mt discovery
  2241                            true,
  2242                                 // Reference discovery is atomic
  2243                            &_is_alive_closure_stw,
  2244                                 // is alive closure
  2245                                 // (for efficiency/performance)
  2246                            false);
  2247                                 // Setting next fields of discovered
  2248                                 // lists requires a barrier.
  2251 size_t G1CollectedHeap::capacity() const {
  2252   return _g1_committed.byte_size();
  2255 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
  2256   assert(!hr->continuesHumongous(), "pre-condition");
  2257   hr->reset_gc_time_stamp();
  2258   if (hr->startsHumongous()) {
  2259     uint first_index = hr->hrs_index() + 1;
  2260     uint last_index = hr->last_hc_index();
  2261     for (uint i = first_index; i < last_index; i += 1) {
  2262       HeapRegion* chr = region_at(i);
  2263       assert(chr->continuesHumongous(), "sanity");
  2264       chr->reset_gc_time_stamp();
  2269 #ifndef PRODUCT
  2270 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
  2271 private:
  2272   unsigned _gc_time_stamp;
  2273   bool _failures;
  2275 public:
  2276   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
  2277     _gc_time_stamp(gc_time_stamp), _failures(false) { }
  2279   virtual bool doHeapRegion(HeapRegion* hr) {
  2280     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
  2281     if (_gc_time_stamp != region_gc_time_stamp) {
  2282       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
  2283                              "expected %d", HR_FORMAT_PARAMS(hr),
  2284                              region_gc_time_stamp, _gc_time_stamp);
  2285       _failures = true;
  2287     return false;
  2290   bool failures() { return _failures; }
  2291 };
  2293 void G1CollectedHeap::check_gc_time_stamps() {
  2294   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
  2295   heap_region_iterate(&cl);
  2296   guarantee(!cl.failures(), "all GC time stamps should have been reset");
  2298 #endif // PRODUCT
  2300 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
  2301                                                  DirtyCardQueue* into_cset_dcq,
  2302                                                  bool concurrent,
  2303                                                  int worker_i) {
  2304   // Clean cards in the hot card cache
  2305   concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
  2307   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
  2308   int n_completed_buffers = 0;
  2309   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
  2310     n_completed_buffers++;
  2312   g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
  2313   dcqs.clear_n_completed_buffers();
  2314   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
  2318 // Computes the sum of the storage used by the various regions.
  2320 size_t G1CollectedHeap::used() const {
  2321   assert(Heap_lock->owner() != NULL,
  2322          "Should be owned on this thread's behalf.");
  2323   size_t result = _summary_bytes_used;
  2324   // Read only once in case it is set to NULL concurrently
  2325   HeapRegion* hr = _mutator_alloc_region.get();
  2326   if (hr != NULL)
  2327     result += hr->used();
  2328   return result;
  2331 size_t G1CollectedHeap::used_unlocked() const {
  2332   size_t result = _summary_bytes_used;
  2333   return result;
  2336 class SumUsedClosure: public HeapRegionClosure {
  2337   size_t _used;
  2338 public:
  2339   SumUsedClosure() : _used(0) {}
  2340   bool doHeapRegion(HeapRegion* r) {
  2341     if (!r->continuesHumongous()) {
  2342       _used += r->used();
  2344     return false;
  2346   size_t result() { return _used; }
  2347 };
  2349 size_t G1CollectedHeap::recalculate_used() const {
  2350   SumUsedClosure blk;
  2351   heap_region_iterate(&blk);
  2352   return blk.result();
  2355 size_t G1CollectedHeap::unsafe_max_alloc() {
  2356   if (free_regions() > 0) return HeapRegion::GrainBytes;
  2357   // otherwise, is there space in the current allocation region?
  2359   // We need to store the current allocation region in a local variable
  2360   // here. The problem is that this method doesn't take any locks and
  2361   // there may be other threads which overwrite the current allocation
  2362   // region field. attempt_allocation(), for example, sets it to NULL
  2363   // and this can happen *after* the NULL check here but before the call
  2364   // to free(), resulting in a SIGSEGV. Note that this doesn't appear
  2365   // to be a problem in the optimized build, since the two loads of the
  2366   // current allocation region field are optimized away.
  2367   HeapRegion* hr = _mutator_alloc_region.get();
  2368   if (hr == NULL) {
  2369     return 0;
  2371   return hr->free();
  2374 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
  2375   switch (cause) {
  2376     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
  2377     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
  2378     case GCCause::_g1_humongous_allocation: return true;
  2379     default:                                return false;
  2383 #ifndef PRODUCT
  2384 void G1CollectedHeap::allocate_dummy_regions() {
  2385   // Let's fill up most of the region
  2386   size_t word_size = HeapRegion::GrainWords - 1024;
  2387   // And as a result the region we'll allocate will be humongous.
  2388   guarantee(isHumongous(word_size), "sanity");
  2390   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
  2391     // Let's use the existing mechanism for the allocation
  2392     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
  2393     if (dummy_obj != NULL) {
  2394       MemRegion mr(dummy_obj, word_size);
  2395       CollectedHeap::fill_with_object(mr);
  2396     } else {
  2397       // If we can't allocate once, we probably cannot allocate
  2398       // again. Let's get out of the loop.
  2399       break;
  2403 #endif // !PRODUCT
  2405 void G1CollectedHeap::increment_old_marking_cycles_started() {
  2406   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
  2407     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
  2408     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
  2409     _old_marking_cycles_started, _old_marking_cycles_completed));
  2411   _old_marking_cycles_started++;
  2414 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
  2415   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
  2417   // We assume that if concurrent == true, then the caller is a
  2418   // concurrent thread that was joined the Suspendible Thread
  2419   // Set. If there's ever a cheap way to check this, we should add an
  2420   // assert here.
  2422   // Given that this method is called at the end of a Full GC or of a
  2423   // concurrent cycle, and those can be nested (i.e., a Full GC can
  2424   // interrupt a concurrent cycle), the number of full collections
  2425   // completed should be either one (in the case where there was no
  2426   // nesting) or two (when a Full GC interrupted a concurrent cycle)
  2427   // behind the number of full collections started.
  2429   // This is the case for the inner caller, i.e. a Full GC.
  2430   assert(concurrent ||
  2431          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
  2432          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
  2433          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
  2434                  "is inconsistent with _old_marking_cycles_completed = %u",
  2435                  _old_marking_cycles_started, _old_marking_cycles_completed));
  2437   // This is the case for the outer caller, i.e. the concurrent cycle.
  2438   assert(!concurrent ||
  2439          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
  2440          err_msg("for outer caller (concurrent cycle): "
  2441                  "_old_marking_cycles_started = %u "
  2442                  "is inconsistent with _old_marking_cycles_completed = %u",
  2443                  _old_marking_cycles_started, _old_marking_cycles_completed));
  2445   _old_marking_cycles_completed += 1;
  2447   // We need to clear the "in_progress" flag in the CM thread before
  2448   // we wake up any waiters (especially when ExplicitInvokesConcurrent
  2449   // is set) so that if a waiter requests another System.gc() it doesn't
  2450   // incorrectly see that a marking cyle is still in progress.
  2451   if (concurrent) {
  2452     _cmThread->clear_in_progress();
  2455   // This notify_all() will ensure that a thread that called
  2456   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
  2457   // and it's waiting for a full GC to finish will be woken up. It is
  2458   // waiting in VM_G1IncCollectionPause::doit_epilogue().
  2459   FullGCCount_lock->notify_all();
  2462 void G1CollectedHeap::collect(GCCause::Cause cause) {
  2463   assert_heap_not_locked();
  2465   unsigned int gc_count_before;
  2466   unsigned int old_marking_count_before;
  2467   bool retry_gc;
  2469   do {
  2470     retry_gc = false;
  2473       MutexLocker ml(Heap_lock);
  2475       // Read the GC count while holding the Heap_lock
  2476       gc_count_before = total_collections();
  2477       old_marking_count_before = _old_marking_cycles_started;
  2480     if (should_do_concurrent_full_gc(cause)) {
  2481       // Schedule an initial-mark evacuation pause that will start a
  2482       // concurrent cycle. We're setting word_size to 0 which means that
  2483       // we are not requesting a post-GC allocation.
  2484       VM_G1IncCollectionPause op(gc_count_before,
  2485                                  0,     /* word_size */
  2486                                  true,  /* should_initiate_conc_mark */
  2487                                  g1_policy()->max_pause_time_ms(),
  2488                                  cause);
  2490       VMThread::execute(&op);
  2491       if (!op.pause_succeeded()) {
  2492         if (old_marking_count_before == _old_marking_cycles_started) {
  2493           retry_gc = op.should_retry_gc();
  2494         } else {
  2495           // A Full GC happened while we were trying to schedule the
  2496           // initial-mark GC. No point in starting a new cycle given
  2497           // that the whole heap was collected anyway.
  2500         if (retry_gc) {
  2501           if (GC_locker::is_active_and_needs_gc()) {
  2502             GC_locker::stall_until_clear();
  2506     } else {
  2507       if (cause == GCCause::_gc_locker
  2508           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
  2510         // Schedule a standard evacuation pause. We're setting word_size
  2511         // to 0 which means that we are not requesting a post-GC allocation.
  2512         VM_G1IncCollectionPause op(gc_count_before,
  2513                                    0,     /* word_size */
  2514                                    false, /* should_initiate_conc_mark */
  2515                                    g1_policy()->max_pause_time_ms(),
  2516                                    cause);
  2517         VMThread::execute(&op);
  2518       } else {
  2519         // Schedule a Full GC.
  2520         VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
  2521         VMThread::execute(&op);
  2524   } while (retry_gc);
  2527 bool G1CollectedHeap::is_in(const void* p) const {
  2528   if (_g1_committed.contains(p)) {
  2529     // Given that we know that p is in the committed space,
  2530     // heap_region_containing_raw() should successfully
  2531     // return the containing region.
  2532     HeapRegion* hr = heap_region_containing_raw(p);
  2533     return hr->is_in(p);
  2534   } else {
  2535     return false;
  2539 // Iteration functions.
  2541 // Iterates an OopClosure over all ref-containing fields of objects
  2542 // within a HeapRegion.
  2544 class IterateOopClosureRegionClosure: public HeapRegionClosure {
  2545   MemRegion _mr;
  2546   ExtendedOopClosure* _cl;
  2547 public:
  2548   IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
  2549     : _mr(mr), _cl(cl) {}
  2550   bool doHeapRegion(HeapRegion* r) {
  2551     if (!r->continuesHumongous()) {
  2552       r->oop_iterate(_cl);
  2554     return false;
  2556 };
  2558 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
  2559   IterateOopClosureRegionClosure blk(_g1_committed, cl);
  2560   heap_region_iterate(&blk);
  2563 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
  2564   IterateOopClosureRegionClosure blk(mr, cl);
  2565   heap_region_iterate(&blk);
  2568 // Iterates an ObjectClosure over all objects within a HeapRegion.
  2570 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
  2571   ObjectClosure* _cl;
  2572 public:
  2573   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
  2574   bool doHeapRegion(HeapRegion* r) {
  2575     if (! r->continuesHumongous()) {
  2576       r->object_iterate(_cl);
  2578     return false;
  2580 };
  2582 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
  2583   IterateObjectClosureRegionClosure blk(cl);
  2584   heap_region_iterate(&blk);
  2587 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
  2588   // FIXME: is this right?
  2589   guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
  2592 // Calls a SpaceClosure on a HeapRegion.
  2594 class SpaceClosureRegionClosure: public HeapRegionClosure {
  2595   SpaceClosure* _cl;
  2596 public:
  2597   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
  2598   bool doHeapRegion(HeapRegion* r) {
  2599     _cl->do_space(r);
  2600     return false;
  2602 };
  2604 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
  2605   SpaceClosureRegionClosure blk(cl);
  2606   heap_region_iterate(&blk);
  2609 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
  2610   _hrs.iterate(cl);
  2613 void
  2614 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
  2615                                                  uint worker_id,
  2616                                                  uint no_of_par_workers,
  2617                                                  jint claim_value) {
  2618   const uint regions = n_regions();
  2619   const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
  2620                              no_of_par_workers :
  2621                              1);
  2622   assert(UseDynamicNumberOfGCThreads ||
  2623          no_of_par_workers == workers()->total_workers(),
  2624          "Non dynamic should use fixed number of workers");
  2625   // try to spread out the starting points of the workers
  2626   const HeapRegion* start_hr =
  2627                         start_region_for_worker(worker_id, no_of_par_workers);
  2628   const uint start_index = start_hr->hrs_index();
  2630   // each worker will actually look at all regions
  2631   for (uint count = 0; count < regions; ++count) {
  2632     const uint index = (start_index + count) % regions;
  2633     assert(0 <= index && index < regions, "sanity");
  2634     HeapRegion* r = region_at(index);
  2635     // we'll ignore "continues humongous" regions (we'll process them
  2636     // when we come across their corresponding "start humongous"
  2637     // region) and regions already claimed
  2638     if (r->claim_value() == claim_value || r->continuesHumongous()) {
  2639       continue;
  2641     // OK, try to claim it
  2642     if (r->claimHeapRegion(claim_value)) {
  2643       // success!
  2644       assert(!r->continuesHumongous(), "sanity");
  2645       if (r->startsHumongous()) {
  2646         // If the region is "starts humongous" we'll iterate over its
  2647         // "continues humongous" first; in fact we'll do them
  2648         // first. The order is important. In on case, calling the
  2649         // closure on the "starts humongous" region might de-allocate
  2650         // and clear all its "continues humongous" regions and, as a
  2651         // result, we might end up processing them twice. So, we'll do
  2652         // them first (notice: most closures will ignore them anyway) and
  2653         // then we'll do the "starts humongous" region.
  2654         for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
  2655           HeapRegion* chr = region_at(ch_index);
  2657           // if the region has already been claimed or it's not
  2658           // "continues humongous" we're done
  2659           if (chr->claim_value() == claim_value ||
  2660               !chr->continuesHumongous()) {
  2661             break;
  2664           // Noone should have claimed it directly. We can given
  2665           // that we claimed its "starts humongous" region.
  2666           assert(chr->claim_value() != claim_value, "sanity");
  2667           assert(chr->humongous_start_region() == r, "sanity");
  2669           if (chr->claimHeapRegion(claim_value)) {
  2670             // we should always be able to claim it; noone else should
  2671             // be trying to claim this region
  2673             bool res2 = cl->doHeapRegion(chr);
  2674             assert(!res2, "Should not abort");
  2676             // Right now, this holds (i.e., no closure that actually
  2677             // does something with "continues humongous" regions
  2678             // clears them). We might have to weaken it in the future,
  2679             // but let's leave these two asserts here for extra safety.
  2680             assert(chr->continuesHumongous(), "should still be the case");
  2681             assert(chr->humongous_start_region() == r, "sanity");
  2682           } else {
  2683             guarantee(false, "we should not reach here");
  2688       assert(!r->continuesHumongous(), "sanity");
  2689       bool res = cl->doHeapRegion(r);
  2690       assert(!res, "Should not abort");
  2695 class ResetClaimValuesClosure: public HeapRegionClosure {
  2696 public:
  2697   bool doHeapRegion(HeapRegion* r) {
  2698     r->set_claim_value(HeapRegion::InitialClaimValue);
  2699     return false;
  2701 };
  2703 void G1CollectedHeap::reset_heap_region_claim_values() {
  2704   ResetClaimValuesClosure blk;
  2705   heap_region_iterate(&blk);
  2708 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
  2709   ResetClaimValuesClosure blk;
  2710   collection_set_iterate(&blk);
  2713 #ifdef ASSERT
  2714 // This checks whether all regions in the heap have the correct claim
  2715 // value. I also piggy-backed on this a check to ensure that the
  2716 // humongous_start_region() information on "continues humongous"
  2717 // regions is correct.
  2719 class CheckClaimValuesClosure : public HeapRegionClosure {
  2720 private:
  2721   jint _claim_value;
  2722   uint _failures;
  2723   HeapRegion* _sh_region;
  2725 public:
  2726   CheckClaimValuesClosure(jint claim_value) :
  2727     _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
  2728   bool doHeapRegion(HeapRegion* r) {
  2729     if (r->claim_value() != _claim_value) {
  2730       gclog_or_tty->print_cr("Region " HR_FORMAT ", "
  2731                              "claim value = %d, should be %d",
  2732                              HR_FORMAT_PARAMS(r),
  2733                              r->claim_value(), _claim_value);
  2734       ++_failures;
  2736     if (!r->isHumongous()) {
  2737       _sh_region = NULL;
  2738     } else if (r->startsHumongous()) {
  2739       _sh_region = r;
  2740     } else if (r->continuesHumongous()) {
  2741       if (r->humongous_start_region() != _sh_region) {
  2742         gclog_or_tty->print_cr("Region " HR_FORMAT ", "
  2743                                "HS = "PTR_FORMAT", should be "PTR_FORMAT,
  2744                                HR_FORMAT_PARAMS(r),
  2745                                r->humongous_start_region(),
  2746                                _sh_region);
  2747         ++_failures;
  2750     return false;
  2752   uint failures() { return _failures; }
  2753 };
  2755 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
  2756   CheckClaimValuesClosure cl(claim_value);
  2757   heap_region_iterate(&cl);
  2758   return cl.failures() == 0;
  2761 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
  2762 private:
  2763   jint _claim_value;
  2764   uint _failures;
  2766 public:
  2767   CheckClaimValuesInCSetHRClosure(jint claim_value) :
  2768     _claim_value(claim_value), _failures(0) { }
  2770   uint failures() { return _failures; }
  2772   bool doHeapRegion(HeapRegion* hr) {
  2773     assert(hr->in_collection_set(), "how?");
  2774     assert(!hr->isHumongous(), "H-region in CSet");
  2775     if (hr->claim_value() != _claim_value) {
  2776       gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
  2777                              "claim value = %d, should be %d",
  2778                              HR_FORMAT_PARAMS(hr),
  2779                              hr->claim_value(), _claim_value);
  2780       _failures += 1;
  2782     return false;
  2784 };
  2786 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
  2787   CheckClaimValuesInCSetHRClosure cl(claim_value);
  2788   collection_set_iterate(&cl);
  2789   return cl.failures() == 0;
  2791 #endif // ASSERT
  2793 // Clear the cached CSet starting regions and (more importantly)
  2794 // the time stamps. Called when we reset the GC time stamp.
  2795 void G1CollectedHeap::clear_cset_start_regions() {
  2796   assert(_worker_cset_start_region != NULL, "sanity");
  2797   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
  2799   int n_queues = MAX2((int)ParallelGCThreads, 1);
  2800   for (int i = 0; i < n_queues; i++) {
  2801     _worker_cset_start_region[i] = NULL;
  2802     _worker_cset_start_region_time_stamp[i] = 0;
  2806 // Given the id of a worker, obtain or calculate a suitable
  2807 // starting region for iterating over the current collection set.
  2808 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
  2809   assert(get_gc_time_stamp() > 0, "should have been updated by now");
  2811   HeapRegion* result = NULL;
  2812   unsigned gc_time_stamp = get_gc_time_stamp();
  2814   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
  2815     // Cached starting region for current worker was set
  2816     // during the current pause - so it's valid.
  2817     // Note: the cached starting heap region may be NULL
  2818     // (when the collection set is empty).
  2819     result = _worker_cset_start_region[worker_i];
  2820     assert(result == NULL || result->in_collection_set(), "sanity");
  2821     return result;
  2824   // The cached entry was not valid so let's calculate
  2825   // a suitable starting heap region for this worker.
  2827   // We want the parallel threads to start their collection
  2828   // set iteration at different collection set regions to
  2829   // avoid contention.
  2830   // If we have:
  2831   //          n collection set regions
  2832   //          p threads
  2833   // Then thread t will start at region floor ((t * n) / p)
  2835   result = g1_policy()->collection_set();
  2836   if (G1CollectedHeap::use_parallel_gc_threads()) {
  2837     uint cs_size = g1_policy()->cset_region_length();
  2838     uint active_workers = workers()->active_workers();
  2839     assert(UseDynamicNumberOfGCThreads ||
  2840              active_workers == workers()->total_workers(),
  2841              "Unless dynamic should use total workers");
  2843     uint end_ind   = (cs_size * worker_i) / active_workers;
  2844     uint start_ind = 0;
  2846     if (worker_i > 0 &&
  2847         _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
  2848       // Previous workers starting region is valid
  2849       // so let's iterate from there
  2850       start_ind = (cs_size * (worker_i - 1)) / active_workers;
  2851       result = _worker_cset_start_region[worker_i - 1];
  2854     for (uint i = start_ind; i < end_ind; i++) {
  2855       result = result->next_in_collection_set();
  2859   // Note: the calculated starting heap region may be NULL
  2860   // (when the collection set is empty).
  2861   assert(result == NULL || result->in_collection_set(), "sanity");
  2862   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
  2863          "should be updated only once per pause");
  2864   _worker_cset_start_region[worker_i] = result;
  2865   OrderAccess::storestore();
  2866   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
  2867   return result;
  2870 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
  2871                                                      uint no_of_par_workers) {
  2872   uint worker_num =
  2873            G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
  2874   assert(UseDynamicNumberOfGCThreads ||
  2875          no_of_par_workers == workers()->total_workers(),
  2876          "Non dynamic should use fixed number of workers");
  2877   const uint start_index = n_regions() * worker_i / worker_num;
  2878   return region_at(start_index);
  2881 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
  2882   HeapRegion* r = g1_policy()->collection_set();
  2883   while (r != NULL) {
  2884     HeapRegion* next = r->next_in_collection_set();
  2885     if (cl->doHeapRegion(r)) {
  2886       cl->incomplete();
  2887       return;
  2889     r = next;
  2893 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
  2894                                                   HeapRegionClosure *cl) {
  2895   if (r == NULL) {
  2896     // The CSet is empty so there's nothing to do.
  2897     return;
  2900   assert(r->in_collection_set(),
  2901          "Start region must be a member of the collection set.");
  2902   HeapRegion* cur = r;
  2903   while (cur != NULL) {
  2904     HeapRegion* next = cur->next_in_collection_set();
  2905     if (cl->doHeapRegion(cur) && false) {
  2906       cl->incomplete();
  2907       return;
  2909     cur = next;
  2911   cur = g1_policy()->collection_set();
  2912   while (cur != r) {
  2913     HeapRegion* next = cur->next_in_collection_set();
  2914     if (cl->doHeapRegion(cur) && false) {
  2915       cl->incomplete();
  2916       return;
  2918     cur = next;
  2922 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
  2923   return n_regions() > 0 ? region_at(0) : NULL;
  2927 Space* G1CollectedHeap::space_containing(const void* addr) const {
  2928   Space* res = heap_region_containing(addr);
  2929   return res;
  2932 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
  2933   Space* sp = space_containing(addr);
  2934   if (sp != NULL) {
  2935     return sp->block_start(addr);
  2937   return NULL;
  2940 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
  2941   Space* sp = space_containing(addr);
  2942   assert(sp != NULL, "block_size of address outside of heap");
  2943   return sp->block_size(addr);
  2946 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
  2947   Space* sp = space_containing(addr);
  2948   return sp->block_is_obj(addr);
  2951 bool G1CollectedHeap::supports_tlab_allocation() const {
  2952   return true;
  2955 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
  2956   return HeapRegion::GrainBytes;
  2959 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
  2960   // Return the remaining space in the cur alloc region, but not less than
  2961   // the min TLAB size.
  2963   // Also, this value can be at most the humongous object threshold,
  2964   // since we can't allow tlabs to grow big enough to accomodate
  2965   // humongous objects.
  2967   HeapRegion* hr = _mutator_alloc_region.get();
  2968   size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
  2969   if (hr == NULL) {
  2970     return max_tlab_size;
  2971   } else {
  2972     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
  2976 size_t G1CollectedHeap::max_capacity() const {
  2977   return _g1_reserved.byte_size();
  2980 jlong G1CollectedHeap::millis_since_last_gc() {
  2981   // assert(false, "NYI");
  2982   return 0;
  2985 void G1CollectedHeap::prepare_for_verify() {
  2986   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
  2987     ensure_parsability(false);
  2989   g1_rem_set()->prepare_for_verify();
  2992 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
  2993                                               VerifyOption vo) {
  2994   switch (vo) {
  2995   case VerifyOption_G1UsePrevMarking:
  2996     return hr->obj_allocated_since_prev_marking(obj);
  2997   case VerifyOption_G1UseNextMarking:
  2998     return hr->obj_allocated_since_next_marking(obj);
  2999   case VerifyOption_G1UseMarkWord:
  3000     return false;
  3001   default:
  3002     ShouldNotReachHere();
  3004   return false; // keep some compilers happy
  3007 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
  3008   switch (vo) {
  3009   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
  3010   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
  3011   case VerifyOption_G1UseMarkWord:    return NULL;
  3012   default:                            ShouldNotReachHere();
  3014   return NULL; // keep some compilers happy
  3017 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
  3018   switch (vo) {
  3019   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
  3020   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
  3021   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
  3022   default:                            ShouldNotReachHere();
  3024   return false; // keep some compilers happy
  3027 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
  3028   switch (vo) {
  3029   case VerifyOption_G1UsePrevMarking: return "PTAMS";
  3030   case VerifyOption_G1UseNextMarking: return "NTAMS";
  3031   case VerifyOption_G1UseMarkWord:    return "NONE";
  3032   default:                            ShouldNotReachHere();
  3034   return NULL; // keep some compilers happy
  3037 class VerifyLivenessOopClosure: public OopClosure {
  3038   G1CollectedHeap* _g1h;
  3039   VerifyOption _vo;
  3040 public:
  3041   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
  3042     _g1h(g1h), _vo(vo)
  3043   { }
  3044   void do_oop(narrowOop *p) { do_oop_work(p); }
  3045   void do_oop(      oop *p) { do_oop_work(p); }
  3047   template <class T> void do_oop_work(T *p) {
  3048     oop obj = oopDesc::load_decode_heap_oop(p);
  3049     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
  3050               "Dead object referenced by a not dead object");
  3052 };
  3054 class VerifyObjsInRegionClosure: public ObjectClosure {
  3055 private:
  3056   G1CollectedHeap* _g1h;
  3057   size_t _live_bytes;
  3058   HeapRegion *_hr;
  3059   VerifyOption _vo;
  3060 public:
  3061   // _vo == UsePrevMarking -> use "prev" marking information,
  3062   // _vo == UseNextMarking -> use "next" marking information,
  3063   // _vo == UseMarkWord    -> use mark word from object header.
  3064   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
  3065     : _live_bytes(0), _hr(hr), _vo(vo) {
  3066     _g1h = G1CollectedHeap::heap();
  3068   void do_object(oop o) {
  3069     VerifyLivenessOopClosure isLive(_g1h, _vo);
  3070     assert(o != NULL, "Huh?");
  3071     if (!_g1h->is_obj_dead_cond(o, _vo)) {
  3072       // If the object is alive according to the mark word,
  3073       // then verify that the marking information agrees.
  3074       // Note we can't verify the contra-positive of the
  3075       // above: if the object is dead (according to the mark
  3076       // word), it may not be marked, or may have been marked
  3077       // but has since became dead, or may have been allocated
  3078       // since the last marking.
  3079       if (_vo == VerifyOption_G1UseMarkWord) {
  3080         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
  3083       o->oop_iterate_no_header(&isLive);
  3084       if (!_hr->obj_allocated_since_prev_marking(o)) {
  3085         size_t obj_size = o->size();    // Make sure we don't overflow
  3086         _live_bytes += (obj_size * HeapWordSize);
  3090   size_t live_bytes() { return _live_bytes; }
  3091 };
  3093 class PrintObjsInRegionClosure : public ObjectClosure {
  3094   HeapRegion *_hr;
  3095   G1CollectedHeap *_g1;
  3096 public:
  3097   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
  3098     _g1 = G1CollectedHeap::heap();
  3099   };
  3101   void do_object(oop o) {
  3102     if (o != NULL) {
  3103       HeapWord *start = (HeapWord *) o;
  3104       size_t word_sz = o->size();
  3105       gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
  3106                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
  3107                           (void*) o, word_sz,
  3108                           _g1->isMarkedPrev(o),
  3109                           _g1->isMarkedNext(o),
  3110                           _hr->obj_allocated_since_prev_marking(o));
  3111       HeapWord *end = start + word_sz;
  3112       HeapWord *cur;
  3113       int *val;
  3114       for (cur = start; cur < end; cur++) {
  3115         val = (int *) cur;
  3116         gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
  3120 };
  3122 class VerifyRegionClosure: public HeapRegionClosure {
  3123 private:
  3124   bool             _par;
  3125   VerifyOption     _vo;
  3126   bool             _failures;
  3127 public:
  3128   // _vo == UsePrevMarking -> use "prev" marking information,
  3129   // _vo == UseNextMarking -> use "next" marking information,
  3130   // _vo == UseMarkWord    -> use mark word from object header.
  3131   VerifyRegionClosure(bool par, VerifyOption vo)
  3132     : _par(par),
  3133       _vo(vo),
  3134       _failures(false) {}
  3136   bool failures() {
  3137     return _failures;
  3140   bool doHeapRegion(HeapRegion* r) {
  3141     if (!r->continuesHumongous()) {
  3142       bool failures = false;
  3143       r->verify(_vo, &failures);
  3144       if (failures) {
  3145         _failures = true;
  3146       } else {
  3147         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
  3148         r->object_iterate(&not_dead_yet_cl);
  3149         if (_vo != VerifyOption_G1UseNextMarking) {
  3150           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
  3151             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
  3152                                    "max_live_bytes "SIZE_FORMAT" "
  3153                                    "< calculated "SIZE_FORMAT,
  3154                                    r->bottom(), r->end(),
  3155                                    r->max_live_bytes(),
  3156                                  not_dead_yet_cl.live_bytes());
  3157             _failures = true;
  3159         } else {
  3160           // When vo == UseNextMarking we cannot currently do a sanity
  3161           // check on the live bytes as the calculation has not been
  3162           // finalized yet.
  3166     return false; // stop the region iteration if we hit a failure
  3168 };
  3170 class YoungRefCounterClosure : public OopClosure {
  3171   G1CollectedHeap* _g1h;
  3172   int              _count;
  3173  public:
  3174   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
  3175   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
  3176   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
  3178   int count() { return _count; }
  3179   void reset_count() { _count = 0; };
  3180 };
  3182 class VerifyKlassClosure: public KlassClosure {
  3183   YoungRefCounterClosure _young_ref_counter_closure;
  3184   OopClosure *_oop_closure;
  3185  public:
  3186   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
  3187   void do_klass(Klass* k) {
  3188     k->oops_do(_oop_closure);
  3190     _young_ref_counter_closure.reset_count();
  3191     k->oops_do(&_young_ref_counter_closure);
  3192     if (_young_ref_counter_closure.count() > 0) {
  3193       guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
  3196 };
  3198 // TODO: VerifyRootsClosure extends OopsInGenClosure so that we can
  3199 //       pass it as the perm_blk to SharedHeap::process_strong_roots.
  3200 //       When process_strong_roots stop calling perm_blk->younger_refs_iterate
  3201 //       we can change this closure to extend the simpler OopClosure.
  3202 class VerifyRootsClosure: public OopsInGenClosure {
  3203 private:
  3204   G1CollectedHeap* _g1h;
  3205   VerifyOption     _vo;
  3206   bool             _failures;
  3207 public:
  3208   // _vo == UsePrevMarking -> use "prev" marking information,
  3209   // _vo == UseNextMarking -> use "next" marking information,
  3210   // _vo == UseMarkWord    -> use mark word from object header.
  3211   VerifyRootsClosure(VerifyOption vo) :
  3212     _g1h(G1CollectedHeap::heap()),
  3213     _vo(vo),
  3214     _failures(false) { }
  3216   bool failures() { return _failures; }
  3218   template <class T> void do_oop_nv(T* p) {
  3219     T heap_oop = oopDesc::load_heap_oop(p);
  3220     if (!oopDesc::is_null(heap_oop)) {
  3221       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
  3222       if (_g1h->is_obj_dead_cond(obj, _vo)) {
  3223         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
  3224                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
  3225         if (_vo == VerifyOption_G1UseMarkWord) {
  3226           gclog_or_tty->print_cr("  Mark word: "PTR_FORMAT, (void*)(obj->mark()));
  3228         obj->print_on(gclog_or_tty);
  3229         _failures = true;
  3234   void do_oop(oop* p)       { do_oop_nv(p); }
  3235   void do_oop(narrowOop* p) { do_oop_nv(p); }
  3236 };
  3238 // This is the task used for parallel heap verification.
  3240 class G1ParVerifyTask: public AbstractGangTask {
  3241 private:
  3242   G1CollectedHeap* _g1h;
  3243   VerifyOption     _vo;
  3244   bool             _failures;
  3246 public:
  3247   // _vo == UsePrevMarking -> use "prev" marking information,
  3248   // _vo == UseNextMarking -> use "next" marking information,
  3249   // _vo == UseMarkWord    -> use mark word from object header.
  3250   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
  3251     AbstractGangTask("Parallel verify task"),
  3252     _g1h(g1h),
  3253     _vo(vo),
  3254     _failures(false) { }
  3256   bool failures() {
  3257     return _failures;
  3260   void work(uint worker_id) {
  3261     HandleMark hm;
  3262     VerifyRegionClosure blk(true, _vo);
  3263     _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
  3264                                           _g1h->workers()->active_workers(),
  3265                                           HeapRegion::ParVerifyClaimValue);
  3266     if (blk.failures()) {
  3267       _failures = true;
  3270 };
  3272 void G1CollectedHeap::verify(bool silent) {
  3273   verify(silent, VerifyOption_G1UsePrevMarking);
  3276 void G1CollectedHeap::verify(bool silent,
  3277                              VerifyOption vo) {
  3278   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
  3279     if (!silent) { gclog_or_tty->print("Roots "); }
  3280     VerifyRootsClosure rootsCl(vo);
  3282     assert(Thread::current()->is_VM_thread(),
  3283       "Expected to be executed serially by the VM thread at this point");
  3285     CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
  3286     VerifyKlassClosure klassCl(this, &rootsCl);
  3288     // We apply the relevant closures to all the oops in the
  3289     // system dictionary, the string table and the code cache.
  3290     const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
  3292     // Need cleared claim bits for the strong roots processing
  3293     ClassLoaderDataGraph::clear_claimed_marks();
  3295     process_strong_roots(true,      // activate StrongRootsScope
  3296                          false,     // we set "is scavenging" to false,
  3297                                     // so we don't reset the dirty cards.
  3298                          ScanningOption(so),  // roots scanning options
  3299                          &rootsCl,
  3300                          &blobsCl,
  3301                          &klassCl
  3302                          );
  3304     bool failures = rootsCl.failures();
  3306     if (vo != VerifyOption_G1UseMarkWord) {
  3307       // If we're verifying during a full GC then the region sets
  3308       // will have been torn down at the start of the GC. Therefore
  3309       // verifying the region sets will fail. So we only verify
  3310       // the region sets when not in a full GC.
  3311       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
  3312       verify_region_sets();
  3315     if (!silent) { gclog_or_tty->print("HeapRegions "); }
  3316     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
  3317       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
  3318              "sanity check");
  3320       G1ParVerifyTask task(this, vo);
  3321       assert(UseDynamicNumberOfGCThreads ||
  3322         workers()->active_workers() == workers()->total_workers(),
  3323         "If not dynamic should be using all the workers");
  3324       int n_workers = workers()->active_workers();
  3325       set_par_threads(n_workers);
  3326       workers()->run_task(&task);
  3327       set_par_threads(0);
  3328       if (task.failures()) {
  3329         failures = true;
  3332       // Checks that the expected amount of parallel work was done.
  3333       // The implication is that n_workers is > 0.
  3334       assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
  3335              "sanity check");
  3337       reset_heap_region_claim_values();
  3339       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
  3340              "sanity check");
  3341     } else {
  3342       VerifyRegionClosure blk(false, vo);
  3343       heap_region_iterate(&blk);
  3344       if (blk.failures()) {
  3345         failures = true;
  3348     if (!silent) gclog_or_tty->print("RemSet ");
  3349     rem_set()->verify();
  3351     if (failures) {
  3352       gclog_or_tty->print_cr("Heap:");
  3353       // It helps to have the per-region information in the output to
  3354       // help us track down what went wrong. This is why we call
  3355       // print_extended_on() instead of print_on().
  3356       print_extended_on(gclog_or_tty);
  3357       gclog_or_tty->print_cr("");
  3358 #ifndef PRODUCT
  3359       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
  3360         concurrent_mark()->print_reachable("at-verification-failure",
  3361                                            vo, false /* all */);
  3363 #endif
  3364       gclog_or_tty->flush();
  3366     guarantee(!failures, "there should not have been any failures");
  3367   } else {
  3368     if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
  3372 class PrintRegionClosure: public HeapRegionClosure {
  3373   outputStream* _st;
  3374 public:
  3375   PrintRegionClosure(outputStream* st) : _st(st) {}
  3376   bool doHeapRegion(HeapRegion* r) {
  3377     r->print_on(_st);
  3378     return false;
  3380 };
  3382 void G1CollectedHeap::print_on(outputStream* st) const {
  3383   st->print(" %-20s", "garbage-first heap");
  3384   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
  3385             capacity()/K, used_unlocked()/K);
  3386   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
  3387             _g1_storage.low_boundary(),
  3388             _g1_storage.high(),
  3389             _g1_storage.high_boundary());
  3390   st->cr();
  3391   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
  3392   uint young_regions = _young_list->length();
  3393   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
  3394             (size_t) young_regions * HeapRegion::GrainBytes / K);
  3395   uint survivor_regions = g1_policy()->recorded_survivor_regions();
  3396   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
  3397             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
  3398   st->cr();
  3401 void G1CollectedHeap::print_extended_on(outputStream* st) const {
  3402   print_on(st);
  3404   // Print the per-region information.
  3405   st->cr();
  3406   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
  3407                "HS=humongous(starts), HC=humongous(continues), "
  3408                "CS=collection set, F=free, TS=gc time stamp, "
  3409                "PTAMS=previous top-at-mark-start, "
  3410                "NTAMS=next top-at-mark-start)");
  3411   PrintRegionClosure blk(st);
  3412   heap_region_iterate(&blk);
  3415 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
  3416   if (G1CollectedHeap::use_parallel_gc_threads()) {
  3417     workers()->print_worker_threads_on(st);
  3419   _cmThread->print_on(st);
  3420   st->cr();
  3421   _cm->print_worker_threads_on(st);
  3422   _cg1r->print_worker_threads_on(st);
  3423   st->cr();
  3426 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
  3427   if (G1CollectedHeap::use_parallel_gc_threads()) {
  3428     workers()->threads_do(tc);
  3430   tc->do_thread(_cmThread);
  3431   _cg1r->threads_do(tc);
  3434 void G1CollectedHeap::print_tracing_info() const {
  3435   // We'll overload this to mean "trace GC pause statistics."
  3436   if (TraceGen0Time || TraceGen1Time) {
  3437     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
  3438     // to that.
  3439     g1_policy()->print_tracing_info();
  3441   if (G1SummarizeRSetStats) {
  3442     g1_rem_set()->print_summary_info();
  3444   if (G1SummarizeConcMark) {
  3445     concurrent_mark()->print_summary_info();
  3447   g1_policy()->print_yg_surv_rate_info();
  3448   SpecializationStats::print();
  3451 #ifndef PRODUCT
  3452 // Helpful for debugging RSet issues.
  3454 class PrintRSetsClosure : public HeapRegionClosure {
  3455 private:
  3456   const char* _msg;
  3457   size_t _occupied_sum;
  3459 public:
  3460   bool doHeapRegion(HeapRegion* r) {
  3461     HeapRegionRemSet* hrrs = r->rem_set();
  3462     size_t occupied = hrrs->occupied();
  3463     _occupied_sum += occupied;
  3465     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
  3466                            HR_FORMAT_PARAMS(r));
  3467     if (occupied == 0) {
  3468       gclog_or_tty->print_cr("  RSet is empty");
  3469     } else {
  3470       hrrs->print();
  3472     gclog_or_tty->print_cr("----------");
  3473     return false;
  3476   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
  3477     gclog_or_tty->cr();
  3478     gclog_or_tty->print_cr("========================================");
  3479     gclog_or_tty->print_cr(msg);
  3480     gclog_or_tty->cr();
  3483   ~PrintRSetsClosure() {
  3484     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
  3485     gclog_or_tty->print_cr("========================================");
  3486     gclog_or_tty->cr();
  3488 };
  3490 void G1CollectedHeap::print_cset_rsets() {
  3491   PrintRSetsClosure cl("Printing CSet RSets");
  3492   collection_set_iterate(&cl);
  3495 void G1CollectedHeap::print_all_rsets() {
  3496   PrintRSetsClosure cl("Printing All RSets");;
  3497   heap_region_iterate(&cl);
  3499 #endif // PRODUCT
  3501 G1CollectedHeap* G1CollectedHeap::heap() {
  3502   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
  3503          "not a garbage-first heap");
  3504   return _g1h;
  3507 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
  3508   // always_do_update_barrier = false;
  3509   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
  3510   // Call allocation profiler
  3511   AllocationProfiler::iterate_since_last_gc();
  3512   // Fill TLAB's and such
  3513   ensure_parsability(true);
  3516 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
  3517   // FIXME: what is this about?
  3518   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
  3519   // is set.
  3520   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
  3521                         "derived pointer present"));
  3522   // always_do_update_barrier = true;
  3524   // We have just completed a GC. Update the soft reference
  3525   // policy with the new heap occupancy
  3526   Universe::update_heap_info_at_gc();
  3529 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
  3530                                                unsigned int gc_count_before,
  3531                                                bool* succeeded) {
  3532   assert_heap_not_locked_and_not_at_safepoint();
  3533   g1_policy()->record_stop_world_start();
  3534   VM_G1IncCollectionPause op(gc_count_before,
  3535                              word_size,
  3536                              false, /* should_initiate_conc_mark */
  3537                              g1_policy()->max_pause_time_ms(),
  3538                              GCCause::_g1_inc_collection_pause);
  3539   VMThread::execute(&op);
  3541   HeapWord* result = op.result();
  3542   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
  3543   assert(result == NULL || ret_succeeded,
  3544          "the result should be NULL if the VM did not succeed");
  3545   *succeeded = ret_succeeded;
  3547   assert_heap_not_locked();
  3548   return result;
  3551 void
  3552 G1CollectedHeap::doConcurrentMark() {
  3553   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
  3554   if (!_cmThread->in_progress()) {
  3555     _cmThread->set_started();
  3556     CGC_lock->notify();
  3560 size_t G1CollectedHeap::pending_card_num() {
  3561   size_t extra_cards = 0;
  3562   JavaThread *curr = Threads::first();
  3563   while (curr != NULL) {
  3564     DirtyCardQueue& dcq = curr->dirty_card_queue();
  3565     extra_cards += dcq.size();
  3566     curr = curr->next();
  3568   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
  3569   size_t buffer_size = dcqs.buffer_size();
  3570   size_t buffer_num = dcqs.completed_buffers_num();
  3572   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
  3573   // in bytes - not the number of 'entries'. We need to convert
  3574   // into a number of cards.
  3575   return (buffer_size * buffer_num + extra_cards) / oopSize;
  3578 size_t G1CollectedHeap::cards_scanned() {
  3579   return g1_rem_set()->cardsScanned();
  3582 void
  3583 G1CollectedHeap::setup_surviving_young_words() {
  3584   assert(_surviving_young_words == NULL, "pre-condition");
  3585   uint array_length = g1_policy()->young_cset_region_length();
  3586   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
  3587   if (_surviving_young_words == NULL) {
  3588     vm_exit_out_of_memory(sizeof(size_t) * array_length,
  3589                           "Not enough space for young surv words summary.");
  3591   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
  3592 #ifdef ASSERT
  3593   for (uint i = 0;  i < array_length; ++i) {
  3594     assert( _surviving_young_words[i] == 0, "memset above" );
  3596 #endif // !ASSERT
  3599 void
  3600 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
  3601   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
  3602   uint array_length = g1_policy()->young_cset_region_length();
  3603   for (uint i = 0; i < array_length; ++i) {
  3604     _surviving_young_words[i] += surv_young_words[i];
  3608 void
  3609 G1CollectedHeap::cleanup_surviving_young_words() {
  3610   guarantee( _surviving_young_words != NULL, "pre-condition" );
  3611   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
  3612   _surviving_young_words = NULL;
  3615 #ifdef ASSERT
  3616 class VerifyCSetClosure: public HeapRegionClosure {
  3617 public:
  3618   bool doHeapRegion(HeapRegion* hr) {
  3619     // Here we check that the CSet region's RSet is ready for parallel
  3620     // iteration. The fields that we'll verify are only manipulated
  3621     // when the region is part of a CSet and is collected. Afterwards,
  3622     // we reset these fields when we clear the region's RSet (when the
  3623     // region is freed) so they are ready when the region is
  3624     // re-allocated. The only exception to this is if there's an
  3625     // evacuation failure and instead of freeing the region we leave
  3626     // it in the heap. In that case, we reset these fields during
  3627     // evacuation failure handling.
  3628     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
  3630     // Here's a good place to add any other checks we'd like to
  3631     // perform on CSet regions.
  3632     return false;
  3634 };
  3635 #endif // ASSERT
  3637 #if TASKQUEUE_STATS
  3638 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
  3639   st->print_raw_cr("GC Task Stats");
  3640   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
  3641   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
  3644 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
  3645   print_taskqueue_stats_hdr(st);
  3647   TaskQueueStats totals;
  3648   const int n = workers() != NULL ? workers()->total_workers() : 1;
  3649   for (int i = 0; i < n; ++i) {
  3650     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
  3651     totals += task_queue(i)->stats;
  3653   st->print_raw("tot "); totals.print(st); st->cr();
  3655   DEBUG_ONLY(totals.verify());
  3658 void G1CollectedHeap::reset_taskqueue_stats() {
  3659   const int n = workers() != NULL ? workers()->total_workers() : 1;
  3660   for (int i = 0; i < n; ++i) {
  3661     task_queue(i)->stats.reset();
  3664 #endif // TASKQUEUE_STATS
  3666 void G1CollectedHeap::log_gc_header() {
  3667   if (!G1Log::fine()) {
  3668     return;
  3671   gclog_or_tty->date_stamp(PrintGCDateStamps);
  3672   gclog_or_tty->stamp(PrintGCTimeStamps);
  3674   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
  3675     .append(g1_policy()->gcs_are_young() ? " (young)" : " (mixed)")
  3676     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
  3678   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
  3681 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
  3682   if (!G1Log::fine()) {
  3683     return;
  3686   if (G1Log::finer()) {
  3687     if (evacuation_failed()) {
  3688       gclog_or_tty->print(" (to-space exhausted)");
  3690     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
  3691     g1_policy()->phase_times()->note_gc_end();
  3692     g1_policy()->phase_times()->print(pause_time_sec);
  3693     g1_policy()->print_detailed_heap_transition();
  3694   } else {
  3695     if (evacuation_failed()) {
  3696       gclog_or_tty->print("--");
  3698     g1_policy()->print_heap_transition();
  3699     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
  3703 bool
  3704 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
  3705   assert_at_safepoint(true /* should_be_vm_thread */);
  3706   guarantee(!is_gc_active(), "collection is not reentrant");
  3708   if (GC_locker::check_active_before_gc()) {
  3709     return false;
  3712   SvcGCMarker sgcm(SvcGCMarker::MINOR);
  3713   ResourceMark rm;
  3715   print_heap_before_gc();
  3717   HRSPhaseSetter x(HRSPhaseEvacuation);
  3718   verify_region_sets_optional();
  3719   verify_dirty_young_regions();
  3721   // This call will decide whether this pause is an initial-mark
  3722   // pause. If it is, during_initial_mark_pause() will return true
  3723   // for the duration of this pause.
  3724   g1_policy()->decide_on_conc_mark_initiation();
  3726   // We do not allow initial-mark to be piggy-backed on a mixed GC.
  3727   assert(!g1_policy()->during_initial_mark_pause() ||
  3728           g1_policy()->gcs_are_young(), "sanity");
  3730   // We also do not allow mixed GCs during marking.
  3731   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
  3733   // Record whether this pause is an initial mark. When the current
  3734   // thread has completed its logging output and it's safe to signal
  3735   // the CM thread, the flag's value in the policy has been reset.
  3736   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
  3738   // Inner scope for scope based logging, timers, and stats collection
  3740     if (g1_policy()->during_initial_mark_pause()) {
  3741       // We are about to start a marking cycle, so we increment the
  3742       // full collection counter.
  3743       increment_old_marking_cycles_started();
  3745     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
  3747     int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
  3748                                 workers()->active_workers() : 1);
  3749     double pause_start_sec = os::elapsedTime();
  3750     g1_policy()->phase_times()->note_gc_start(active_workers);
  3751     log_gc_header();
  3753     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
  3754     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
  3756     // If the secondary_free_list is not empty, append it to the
  3757     // free_list. No need to wait for the cleanup operation to finish;
  3758     // the region allocation code will check the secondary_free_list
  3759     // and wait if necessary. If the G1StressConcRegionFreeing flag is
  3760     // set, skip this step so that the region allocation code has to
  3761     // get entries from the secondary_free_list.
  3762     if (!G1StressConcRegionFreeing) {
  3763       append_secondary_free_list_if_not_empty_with_lock();
  3766     assert(check_young_list_well_formed(),
  3767       "young list should be well formed");
  3769     // Don't dynamically change the number of GC threads this early.  A value of
  3770     // 0 is used to indicate serial work.  When parallel work is done,
  3771     // it will be set.
  3773     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
  3774       IsGCActiveMark x;
  3776       gc_prologue(false);
  3777       increment_total_collections(false /* full gc */);
  3778       increment_gc_time_stamp();
  3780       verify_before_gc();
  3782       COMPILER2_PRESENT(DerivedPointerTable::clear());
  3784       // Please see comment in g1CollectedHeap.hpp and
  3785       // G1CollectedHeap::ref_processing_init() to see how
  3786       // reference processing currently works in G1.
  3788       // Enable discovery in the STW reference processor
  3789       ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
  3790                                             true /*verify_no_refs*/);
  3793         // We want to temporarily turn off discovery by the
  3794         // CM ref processor, if necessary, and turn it back on
  3795         // on again later if we do. Using a scoped
  3796         // NoRefDiscovery object will do this.
  3797         NoRefDiscovery no_cm_discovery(ref_processor_cm());
  3799         // Forget the current alloc region (we might even choose it to be part
  3800         // of the collection set!).
  3801         release_mutator_alloc_region();
  3803         // We should call this after we retire the mutator alloc
  3804         // region(s) so that all the ALLOC / RETIRE events are generated
  3805         // before the start GC event.
  3806         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
  3808         // This timing is only used by the ergonomics to handle our pause target.
  3809         // It is unclear why this should not include the full pause. We will
  3810         // investigate this in CR 7178365.
  3811         //
  3812         // Preserving the old comment here if that helps the investigation:
  3813         //
  3814         // The elapsed time induced by the start time below deliberately elides
  3815         // the possible verification above.
  3816         double sample_start_time_sec = os::elapsedTime();
  3817         size_t start_used_bytes = used();
  3819 #if YOUNG_LIST_VERBOSE
  3820         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
  3821         _young_list->print();
  3822         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
  3823 #endif // YOUNG_LIST_VERBOSE
  3825         g1_policy()->record_collection_pause_start(sample_start_time_sec,
  3826                                                    start_used_bytes);
  3828         double scan_wait_start = os::elapsedTime();
  3829         // We have to wait until the CM threads finish scanning the
  3830         // root regions as it's the only way to ensure that all the
  3831         // objects on them have been correctly scanned before we start
  3832         // moving them during the GC.
  3833         bool waited = _cm->root_regions()->wait_until_scan_finished();
  3834         double wait_time_ms = 0.0;
  3835         if (waited) {
  3836           double scan_wait_end = os::elapsedTime();
  3837           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
  3839         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
  3841 #if YOUNG_LIST_VERBOSE
  3842         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
  3843         _young_list->print();
  3844 #endif // YOUNG_LIST_VERBOSE
  3846         if (g1_policy()->during_initial_mark_pause()) {
  3847           concurrent_mark()->checkpointRootsInitialPre();
  3850 #if YOUNG_LIST_VERBOSE
  3851         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
  3852         _young_list->print();
  3853         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
  3854 #endif // YOUNG_LIST_VERBOSE
  3856         g1_policy()->finalize_cset(target_pause_time_ms);
  3858         _cm->note_start_of_gc();
  3859         // We should not verify the per-thread SATB buffers given that
  3860         // we have not filtered them yet (we'll do so during the
  3861         // GC). We also call this after finalize_cset() to
  3862         // ensure that the CSet has been finalized.
  3863         _cm->verify_no_cset_oops(true  /* verify_stacks */,
  3864                                  true  /* verify_enqueued_buffers */,
  3865                                  false /* verify_thread_buffers */,
  3866                                  true  /* verify_fingers */);
  3868         if (_hr_printer.is_active()) {
  3869           HeapRegion* hr = g1_policy()->collection_set();
  3870           while (hr != NULL) {
  3871             G1HRPrinter::RegionType type;
  3872             if (!hr->is_young()) {
  3873               type = G1HRPrinter::Old;
  3874             } else if (hr->is_survivor()) {
  3875               type = G1HRPrinter::Survivor;
  3876             } else {
  3877               type = G1HRPrinter::Eden;
  3879             _hr_printer.cset(hr);
  3880             hr = hr->next_in_collection_set();
  3884 #ifdef ASSERT
  3885         VerifyCSetClosure cl;
  3886         collection_set_iterate(&cl);
  3887 #endif // ASSERT
  3889         setup_surviving_young_words();
  3891         // Initialize the GC alloc regions.
  3892         init_gc_alloc_regions();
  3894         // Actually do the work...
  3895         evacuate_collection_set();
  3897         // We do this to mainly verify the per-thread SATB buffers
  3898         // (which have been filtered by now) since we didn't verify
  3899         // them earlier. No point in re-checking the stacks / enqueued
  3900         // buffers given that the CSet has not changed since last time
  3901         // we checked.
  3902         _cm->verify_no_cset_oops(false /* verify_stacks */,
  3903                                  false /* verify_enqueued_buffers */,
  3904                                  true  /* verify_thread_buffers */,
  3905                                  true  /* verify_fingers */);
  3907         free_collection_set(g1_policy()->collection_set());
  3908         g1_policy()->clear_collection_set();
  3910         cleanup_surviving_young_words();
  3912         // Start a new incremental collection set for the next pause.
  3913         g1_policy()->start_incremental_cset_building();
  3915         // Clear the _cset_fast_test bitmap in anticipation of adding
  3916         // regions to the incremental collection set for the next
  3917         // evacuation pause.
  3918         clear_cset_fast_test();
  3920         _young_list->reset_sampled_info();
  3922         // Don't check the whole heap at this point as the
  3923         // GC alloc regions from this pause have been tagged
  3924         // as survivors and moved on to the survivor list.
  3925         // Survivor regions will fail the !is_young() check.
  3926         assert(check_young_list_empty(false /* check_heap */),
  3927           "young list should be empty");
  3929 #if YOUNG_LIST_VERBOSE
  3930         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
  3931         _young_list->print();
  3932 #endif // YOUNG_LIST_VERBOSE
  3934         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
  3935                                             _young_list->first_survivor_region(),
  3936                                             _young_list->last_survivor_region());
  3938         _young_list->reset_auxilary_lists();
  3940         if (evacuation_failed()) {
  3941           _summary_bytes_used = recalculate_used();
  3942         } else {
  3943           // The "used" of the the collection set have already been subtracted
  3944           // when they were freed.  Add in the bytes evacuated.
  3945           _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
  3948         if (g1_policy()->during_initial_mark_pause()) {
  3949           // We have to do this before we notify the CM threads that
  3950           // they can start working to make sure that all the
  3951           // appropriate initialization is done on the CM object.
  3952           concurrent_mark()->checkpointRootsInitialPost();
  3953           set_marking_started();
  3954           // Note that we don't actually trigger the CM thread at
  3955           // this point. We do that later when we're sure that
  3956           // the current thread has completed its logging output.
  3959         allocate_dummy_regions();
  3961 #if YOUNG_LIST_VERBOSE
  3962         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
  3963         _young_list->print();
  3964         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
  3965 #endif // YOUNG_LIST_VERBOSE
  3967         init_mutator_alloc_region();
  3970           size_t expand_bytes = g1_policy()->expansion_amount();
  3971           if (expand_bytes > 0) {
  3972             size_t bytes_before = capacity();
  3973             // No need for an ergo verbose message here,
  3974             // expansion_amount() does this when it returns a value > 0.
  3975             if (!expand(expand_bytes)) {
  3976               // We failed to expand the heap so let's verify that
  3977               // committed/uncommitted amount match the backing store
  3978               assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
  3979               assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
  3984         // We redo the verificaiton but now wrt to the new CSet which
  3985         // has just got initialized after the previous CSet was freed.
  3986         _cm->verify_no_cset_oops(true  /* verify_stacks */,
  3987                                  true  /* verify_enqueued_buffers */,
  3988                                  true  /* verify_thread_buffers */,
  3989                                  true  /* verify_fingers */);
  3990         _cm->note_end_of_gc();
  3992         // This timing is only used by the ergonomics to handle our pause target.
  3993         // It is unclear why this should not include the full pause. We will
  3994         // investigate this in CR 7178365.
  3995         double sample_end_time_sec = os::elapsedTime();
  3996         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
  3997         g1_policy()->record_collection_pause_end(pause_time_ms);
  3999         MemoryService::track_memory_usage();
  4001         // In prepare_for_verify() below we'll need to scan the deferred
  4002         // update buffers to bring the RSets up-to-date if
  4003         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
  4004         // the update buffers we'll probably need to scan cards on the
  4005         // regions we just allocated to (i.e., the GC alloc
  4006         // regions). However, during the last GC we called
  4007         // set_saved_mark() on all the GC alloc regions, so card
  4008         // scanning might skip the [saved_mark_word()...top()] area of
  4009         // those regions (i.e., the area we allocated objects into
  4010         // during the last GC). But it shouldn't. Given that
  4011         // saved_mark_word() is conditional on whether the GC time stamp
  4012         // on the region is current or not, by incrementing the GC time
  4013         // stamp here we invalidate all the GC time stamps on all the
  4014         // regions and saved_mark_word() will simply return top() for
  4015         // all the regions. This is a nicer way of ensuring this rather
  4016         // than iterating over the regions and fixing them. In fact, the
  4017         // GC time stamp increment here also ensures that
  4018         // saved_mark_word() will return top() between pauses, i.e.,
  4019         // during concurrent refinement. So we don't need the
  4020         // is_gc_active() check to decided which top to use when
  4021         // scanning cards (see CR 7039627).
  4022         increment_gc_time_stamp();
  4024         verify_after_gc();
  4026         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
  4027         ref_processor_stw()->verify_no_references_recorded();
  4029         // CM reference discovery will be re-enabled if necessary.
  4032       // We should do this after we potentially expand the heap so
  4033       // that all the COMMIT events are generated before the end GC
  4034       // event, and after we retire the GC alloc regions so that all
  4035       // RETIRE events are generated before the end GC event.
  4036       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
  4038       if (mark_in_progress()) {
  4039         concurrent_mark()->update_g1_committed();
  4042 #ifdef TRACESPINNING
  4043       ParallelTaskTerminator::print_termination_counts();
  4044 #endif
  4046       gc_epilogue(false);
  4048       log_gc_footer(os::elapsedTime() - pause_start_sec);
  4051     // It is not yet to safe to tell the concurrent mark to
  4052     // start as we have some optional output below. We don't want the
  4053     // output from the concurrent mark thread interfering with this
  4054     // logging output either.
  4056     _hrs.verify_optional();
  4057     verify_region_sets_optional();
  4059     TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
  4060     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
  4062     print_heap_after_gc();
  4064     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
  4065     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
  4066     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
  4067     // before any GC notifications are raised.
  4068     g1mm()->update_sizes();
  4071   if (G1SummarizeRSetStats &&
  4072       (G1SummarizeRSetStatsPeriod > 0) &&
  4073       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
  4074     g1_rem_set()->print_summary_info();
  4077   // It should now be safe to tell the concurrent mark thread to start
  4078   // without its logging output interfering with the logging output
  4079   // that came from the pause.
  4081   if (should_start_conc_mark) {
  4082     // CAUTION: after the doConcurrentMark() call below,
  4083     // the concurrent marking thread(s) could be running
  4084     // concurrently with us. Make sure that anything after
  4085     // this point does not assume that we are the only GC thread
  4086     // running. Note: of course, the actual marking work will
  4087     // not start until the safepoint itself is released in
  4088     // ConcurrentGCThread::safepoint_desynchronize().
  4089     doConcurrentMark();
  4092   return true;
  4095 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
  4097   size_t gclab_word_size;
  4098   switch (purpose) {
  4099     case GCAllocForSurvived:
  4100       gclab_word_size = _survivor_plab_stats.desired_plab_sz();
  4101       break;
  4102     case GCAllocForTenured:
  4103       gclab_word_size = _old_plab_stats.desired_plab_sz();
  4104       break;
  4105     default:
  4106       assert(false, "unknown GCAllocPurpose");
  4107       gclab_word_size = _old_plab_stats.desired_plab_sz();
  4108       break;
  4111   // Prevent humongous PLAB sizes for two reasons:
  4112   // * PLABs are allocated using a similar paths as oops, but should
  4113   //   never be in a humongous region
  4114   // * Allowing humongous PLABs needlessly churns the region free lists
  4115   return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
  4118 void G1CollectedHeap::init_mutator_alloc_region() {
  4119   assert(_mutator_alloc_region.get() == NULL, "pre-condition");
  4120   _mutator_alloc_region.init();
  4123 void G1CollectedHeap::release_mutator_alloc_region() {
  4124   _mutator_alloc_region.release();
  4125   assert(_mutator_alloc_region.get() == NULL, "post-condition");
  4128 void G1CollectedHeap::init_gc_alloc_regions() {
  4129   assert_at_safepoint(true /* should_be_vm_thread */);
  4131   _survivor_gc_alloc_region.init();
  4132   _old_gc_alloc_region.init();
  4133   HeapRegion* retained_region = _retained_old_gc_alloc_region;
  4134   _retained_old_gc_alloc_region = NULL;
  4136   // We will discard the current GC alloc region if:
  4137   // a) it's in the collection set (it can happen!),
  4138   // b) it's already full (no point in using it),
  4139   // c) it's empty (this means that it was emptied during
  4140   // a cleanup and it should be on the free list now), or
  4141   // d) it's humongous (this means that it was emptied
  4142   // during a cleanup and was added to the free list, but
  4143   // has been subseqently used to allocate a humongous
  4144   // object that may be less than the region size).
  4145   if (retained_region != NULL &&
  4146       !retained_region->in_collection_set() &&
  4147       !(retained_region->top() == retained_region->end()) &&
  4148       !retained_region->is_empty() &&
  4149       !retained_region->isHumongous()) {
  4150     retained_region->set_saved_mark();
  4151     // The retained region was added to the old region set when it was
  4152     // retired. We have to remove it now, since we don't allow regions
  4153     // we allocate to in the region sets. We'll re-add it later, when
  4154     // it's retired again.
  4155     _old_set.remove(retained_region);
  4156     bool during_im = g1_policy()->during_initial_mark_pause();
  4157     retained_region->note_start_of_copying(during_im);
  4158     _old_gc_alloc_region.set(retained_region);
  4159     _hr_printer.reuse(retained_region);
  4163 void G1CollectedHeap::release_gc_alloc_regions() {
  4164   _survivor_gc_alloc_region.release();
  4165   // If we have an old GC alloc region to release, we'll save it in
  4166   // _retained_old_gc_alloc_region. If we don't
  4167   // _retained_old_gc_alloc_region will become NULL. This is what we
  4168   // want either way so no reason to check explicitly for either
  4169   // condition.
  4170   _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
  4172   if (ResizePLAB) {
  4173     _survivor_plab_stats.adjust_desired_plab_sz();
  4174     _old_plab_stats.adjust_desired_plab_sz();
  4178 void G1CollectedHeap::abandon_gc_alloc_regions() {
  4179   assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
  4180   assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
  4181   _retained_old_gc_alloc_region = NULL;
  4184 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
  4185   _drain_in_progress = false;
  4186   set_evac_failure_closure(cl);
  4187   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
  4190 void G1CollectedHeap::finalize_for_evac_failure() {
  4191   assert(_evac_failure_scan_stack != NULL &&
  4192          _evac_failure_scan_stack->length() == 0,
  4193          "Postcondition");
  4194   assert(!_drain_in_progress, "Postcondition");
  4195   delete _evac_failure_scan_stack;
  4196   _evac_failure_scan_stack = NULL;
  4199 void G1CollectedHeap::remove_self_forwarding_pointers() {
  4200   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
  4202   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
  4204   if (G1CollectedHeap::use_parallel_gc_threads()) {
  4205     set_par_threads();
  4206     workers()->run_task(&rsfp_task);
  4207     set_par_threads(0);
  4208   } else {
  4209     rsfp_task.work(0);
  4212   assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
  4214   // Reset the claim values in the regions in the collection set.
  4215   reset_cset_heap_region_claim_values();
  4217   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
  4219   // Now restore saved marks, if any.
  4220   if (_objs_with_preserved_marks != NULL) {
  4221     assert(_preserved_marks_of_objs != NULL, "Both or none.");
  4222     guarantee(_objs_with_preserved_marks->length() ==
  4223               _preserved_marks_of_objs->length(), "Both or none.");
  4224     for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
  4225       oop obj   = _objs_with_preserved_marks->at(i);
  4226       markOop m = _preserved_marks_of_objs->at(i);
  4227       obj->set_mark(m);
  4230     // Delete the preserved marks growable arrays (allocated on the C heap).
  4231     delete _objs_with_preserved_marks;
  4232     delete _preserved_marks_of_objs;
  4233     _objs_with_preserved_marks = NULL;
  4234     _preserved_marks_of_objs = NULL;
  4238 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
  4239   _evac_failure_scan_stack->push(obj);
  4242 void G1CollectedHeap::drain_evac_failure_scan_stack() {
  4243   assert(_evac_failure_scan_stack != NULL, "precondition");
  4245   while (_evac_failure_scan_stack->length() > 0) {
  4246      oop obj = _evac_failure_scan_stack->pop();
  4247      _evac_failure_closure->set_region(heap_region_containing(obj));
  4248      obj->oop_iterate_backwards(_evac_failure_closure);
  4252 oop
  4253 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
  4254                                                oop old) {
  4255   assert(obj_in_cs(old),
  4256          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
  4257                  (HeapWord*) old));
  4258   markOop m = old->mark();
  4259   oop forward_ptr = old->forward_to_atomic(old);
  4260   if (forward_ptr == NULL) {
  4261     // Forward-to-self succeeded.
  4263     if (_evac_failure_closure != cl) {
  4264       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
  4265       assert(!_drain_in_progress,
  4266              "Should only be true while someone holds the lock.");
  4267       // Set the global evac-failure closure to the current thread's.
  4268       assert(_evac_failure_closure == NULL, "Or locking has failed.");
  4269       set_evac_failure_closure(cl);
  4270       // Now do the common part.
  4271       handle_evacuation_failure_common(old, m);
  4272       // Reset to NULL.
  4273       set_evac_failure_closure(NULL);
  4274     } else {
  4275       // The lock is already held, and this is recursive.
  4276       assert(_drain_in_progress, "This should only be the recursive case.");
  4277       handle_evacuation_failure_common(old, m);
  4279     return old;
  4280   } else {
  4281     // Forward-to-self failed. Either someone else managed to allocate
  4282     // space for this object (old != forward_ptr) or they beat us in
  4283     // self-forwarding it (old == forward_ptr).
  4284     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
  4285            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
  4286                    "should not be in the CSet",
  4287                    (HeapWord*) old, (HeapWord*) forward_ptr));
  4288     return forward_ptr;
  4292 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
  4293   set_evacuation_failed(true);
  4295   preserve_mark_if_necessary(old, m);
  4297   HeapRegion* r = heap_region_containing(old);
  4298   if (!r->evacuation_failed()) {
  4299     r->set_evacuation_failed(true);
  4300     _hr_printer.evac_failure(r);
  4303   push_on_evac_failure_scan_stack(old);
  4305   if (!_drain_in_progress) {
  4306     // prevent recursion in copy_to_survivor_space()
  4307     _drain_in_progress = true;
  4308     drain_evac_failure_scan_stack();
  4309     _drain_in_progress = false;
  4313 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
  4314   assert(evacuation_failed(), "Oversaving!");
  4315   // We want to call the "for_promotion_failure" version only in the
  4316   // case of a promotion failure.
  4317   if (m->must_be_preserved_for_promotion_failure(obj)) {
  4318     if (_objs_with_preserved_marks == NULL) {
  4319       assert(_preserved_marks_of_objs == NULL, "Both or none.");
  4320       _objs_with_preserved_marks =
  4321         new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
  4322       _preserved_marks_of_objs =
  4323         new (ResourceObj::C_HEAP, mtGC) GrowableArray<markOop>(40, true);
  4325     _objs_with_preserved_marks->push(obj);
  4326     _preserved_marks_of_objs->push(m);
  4330 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
  4331                                                   size_t word_size) {
  4332   if (purpose == GCAllocForSurvived) {
  4333     HeapWord* result = survivor_attempt_allocation(word_size);
  4334     if (result != NULL) {
  4335       return result;
  4336     } else {
  4337       // Let's try to allocate in the old gen in case we can fit the
  4338       // object there.
  4339       return old_attempt_allocation(word_size);
  4341   } else {
  4342     assert(purpose ==  GCAllocForTenured, "sanity");
  4343     HeapWord* result = old_attempt_allocation(word_size);
  4344     if (result != NULL) {
  4345       return result;
  4346     } else {
  4347       // Let's try to allocate in the survivors in case we can fit the
  4348       // object there.
  4349       return survivor_attempt_allocation(word_size);
  4353   ShouldNotReachHere();
  4354   // Trying to keep some compilers happy.
  4355   return NULL;
  4358 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
  4359   ParGCAllocBuffer(gclab_word_size), _retired(false) { }
  4361 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
  4362   : _g1h(g1h),
  4363     _refs(g1h->task_queue(queue_num)),
  4364     _dcq(&g1h->dirty_card_queue_set()),
  4365     _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
  4366     _g1_rem(g1h->g1_rem_set()),
  4367     _hash_seed(17), _queue_num(queue_num),
  4368     _term_attempts(0),
  4369     _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
  4370     _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
  4371     _age_table(false),
  4372     _strong_roots_time(0), _term_time(0),
  4373     _alloc_buffer_waste(0), _undo_waste(0) {
  4374   // we allocate G1YoungSurvRateNumRegions plus one entries, since
  4375   // we "sacrifice" entry 0 to keep track of surviving bytes for
  4376   // non-young regions (where the age is -1)
  4377   // We also add a few elements at the beginning and at the end in
  4378   // an attempt to eliminate cache contention
  4379   uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
  4380   uint array_length = PADDING_ELEM_NUM +
  4381                       real_length +
  4382                       PADDING_ELEM_NUM;
  4383   _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
  4384   if (_surviving_young_words_base == NULL)
  4385     vm_exit_out_of_memory(array_length * sizeof(size_t),
  4386                           "Not enough space for young surv histo.");
  4387   _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
  4388   memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
  4390   _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
  4391   _alloc_buffers[GCAllocForTenured]  = &_tenured_alloc_buffer;
  4393   _start = os::elapsedTime();
  4396 void
  4397 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
  4399   st->print_raw_cr("GC Termination Stats");
  4400   st->print_raw_cr("     elapsed  --strong roots-- -------termination-------"
  4401                    " ------waste (KiB)------");
  4402   st->print_raw_cr("thr     ms        ms      %        ms      %    attempts"
  4403                    "  total   alloc    undo");
  4404   st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
  4405                    " ------- ------- -------");
  4408 void
  4409 G1ParScanThreadState::print_termination_stats(int i,
  4410                                               outputStream* const st) const
  4412   const double elapsed_ms = elapsed_time() * 1000.0;
  4413   const double s_roots_ms = strong_roots_time() * 1000.0;
  4414   const double term_ms    = term_time() * 1000.0;
  4415   st->print_cr("%3d %9.2f %9.2f %6.2f "
  4416                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
  4417                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
  4418                i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
  4419                term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
  4420                (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
  4421                alloc_buffer_waste() * HeapWordSize / K,
  4422                undo_waste() * HeapWordSize / K);
  4425 #ifdef ASSERT
  4426 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
  4427   assert(ref != NULL, "invariant");
  4428   assert(UseCompressedOops, "sanity");
  4429   assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
  4430   oop p = oopDesc::load_decode_heap_oop(ref);
  4431   assert(_g1h->is_in_g1_reserved(p),
  4432          err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
  4433   return true;
  4436 bool G1ParScanThreadState::verify_ref(oop* ref) const {
  4437   assert(ref != NULL, "invariant");
  4438   if (has_partial_array_mask(ref)) {
  4439     // Must be in the collection set--it's already been copied.
  4440     oop p = clear_partial_array_mask(ref);
  4441     assert(_g1h->obj_in_cs(p),
  4442            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
  4443   } else {
  4444     oop p = oopDesc::load_decode_heap_oop(ref);
  4445     assert(_g1h->is_in_g1_reserved(p),
  4446            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
  4448   return true;
  4451 bool G1ParScanThreadState::verify_task(StarTask ref) const {
  4452   if (ref.is_narrow()) {
  4453     return verify_ref((narrowOop*) ref);
  4454   } else {
  4455     return verify_ref((oop*) ref);
  4458 #endif // ASSERT
  4460 void G1ParScanThreadState::trim_queue() {
  4461   assert(_evac_cl != NULL, "not set");
  4462   assert(_evac_failure_cl != NULL, "not set");
  4463   assert(_partial_scan_cl != NULL, "not set");
  4465   StarTask ref;
  4466   do {
  4467     // Drain the overflow stack first, so other threads can steal.
  4468     while (refs()->pop_overflow(ref)) {
  4469       deal_with_reference(ref);
  4472     while (refs()->pop_local(ref)) {
  4473       deal_with_reference(ref);
  4475   } while (!refs()->is_empty());
  4478 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
  4479                                      G1ParScanThreadState* par_scan_state) :
  4480   _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
  4481   _par_scan_state(par_scan_state),
  4482   _worker_id(par_scan_state->queue_num()),
  4483   _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
  4484   _mark_in_progress(_g1->mark_in_progress()) { }
  4486 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
  4487 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
  4488 #ifdef ASSERT
  4489   HeapRegion* hr = _g1->heap_region_containing(obj);
  4490   assert(hr != NULL, "sanity");
  4491   assert(!hr->in_collection_set(), "should not mark objects in the CSet");
  4492 #endif // ASSERT
  4494   // We know that the object is not moving so it's safe to read its size.
  4495   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
  4498 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
  4499 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
  4500   ::mark_forwarded_object(oop from_obj, oop to_obj) {
  4501 #ifdef ASSERT
  4502   assert(from_obj->is_forwarded(), "from obj should be forwarded");
  4503   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
  4504   assert(from_obj != to_obj, "should not be self-forwarded");
  4506   HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
  4507   assert(from_hr != NULL, "sanity");
  4508   assert(from_hr->in_collection_set(), "from obj should be in the CSet");
  4510   HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
  4511   assert(to_hr != NULL, "sanity");
  4512   assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
  4513 #endif // ASSERT
  4515   // The object might be in the process of being copied by another
  4516   // worker so we cannot trust that its to-space image is
  4517   // well-formed. So we have to read its size from its from-space
  4518   // image which we know should not be changing.
  4519   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
  4522 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
  4523 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
  4524   ::copy_to_survivor_space(oop old) {
  4525   size_t word_sz = old->size();
  4526   HeapRegion* from_region = _g1->heap_region_containing_raw(old);
  4527   // +1 to make the -1 indexes valid...
  4528   int       young_index = from_region->young_index_in_cset()+1;
  4529   assert( (from_region->is_young() && young_index >  0) ||
  4530          (!from_region->is_young() && young_index == 0), "invariant" );
  4531   G1CollectorPolicy* g1p = _g1->g1_policy();
  4532   markOop m = old->mark();
  4533   int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
  4534                                            : m->age();
  4535   GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
  4536                                                              word_sz);
  4537   HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
  4538 #ifndef PRODUCT
  4539   // Should this evacuation fail?
  4540   if (_g1->evacuation_should_fail()) {
  4541     if (obj_ptr != NULL) {
  4542       _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
  4543       obj_ptr = NULL;
  4546 #endif // !PRODUCT
  4548   if (obj_ptr == NULL) {
  4549     // This will either forward-to-self, or detect that someone else has
  4550     // installed a forwarding pointer.
  4551     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
  4552     return _g1->handle_evacuation_failure_par(cl, old);
  4555   oop obj = oop(obj_ptr);
  4557   // We're going to allocate linearly, so might as well prefetch ahead.
  4558   Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
  4560   oop forward_ptr = old->forward_to_atomic(obj);
  4561   if (forward_ptr == NULL) {
  4562     Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
  4563     if (g1p->track_object_age(alloc_purpose)) {
  4564       // We could simply do obj->incr_age(). However, this causes a
  4565       // performance issue. obj->incr_age() will first check whether
  4566       // the object has a displaced mark by checking its mark word;
  4567       // getting the mark word from the new location of the object
  4568       // stalls. So, given that we already have the mark word and we
  4569       // are about to install it anyway, it's better to increase the
  4570       // age on the mark word, when the object does not have a
  4571       // displaced mark word. We're not expecting many objects to have
  4572       // a displaced marked word, so that case is not optimized
  4573       // further (it could be...) and we simply call obj->incr_age().
  4575       if (m->has_displaced_mark_helper()) {
  4576         // in this case, we have to install the mark word first,
  4577         // otherwise obj looks to be forwarded (the old mark word,
  4578         // which contains the forward pointer, was copied)
  4579         obj->set_mark(m);
  4580         obj->incr_age();
  4581       } else {
  4582         m = m->incr_age();
  4583         obj->set_mark(m);
  4585       _par_scan_state->age_table()->add(obj, word_sz);
  4586     } else {
  4587       obj->set_mark(m);
  4590     size_t* surv_young_words = _par_scan_state->surviving_young_words();
  4591     surv_young_words[young_index] += word_sz;
  4593     if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
  4594       // We keep track of the next start index in the length field of
  4595       // the to-space object. The actual length can be found in the
  4596       // length field of the from-space object.
  4597       arrayOop(obj)->set_length(0);
  4598       oop* old_p = set_partial_array_mask(old);
  4599       _par_scan_state->push_on_queue(old_p);
  4600     } else {
  4601       // No point in using the slower heap_region_containing() method,
  4602       // given that we know obj is in the heap.
  4603       _scanner.set_region(_g1->heap_region_containing_raw(obj));
  4604       obj->oop_iterate_backwards(&_scanner);
  4606   } else {
  4607     _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
  4608     obj = forward_ptr;
  4610   return obj;
  4613 template <class T>
  4614 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
  4615   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
  4616     _scanned_klass->record_modified_oops();
  4620 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
  4621 template <class T>
  4622 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
  4623 ::do_oop_work(T* p) {
  4624   oop obj = oopDesc::load_decode_heap_oop(p);
  4625   assert(barrier != G1BarrierRS || obj != NULL,
  4626          "Precondition: G1BarrierRS implies obj is non-NULL");
  4628   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
  4630   // here the null check is implicit in the cset_fast_test() test
  4631   if (_g1->in_cset_fast_test(obj)) {
  4632     oop forwardee;
  4633     if (obj->is_forwarded()) {
  4634       forwardee = obj->forwardee();
  4635     } else {
  4636       forwardee = copy_to_survivor_space(obj);
  4638     assert(forwardee != NULL, "forwardee should not be NULL");
  4639     oopDesc::encode_store_heap_oop(p, forwardee);
  4640     if (do_mark_object && forwardee != obj) {
  4641       // If the object is self-forwarded we don't need to explicitly
  4642       // mark it, the evacuation failure protocol will do so.
  4643       mark_forwarded_object(obj, forwardee);
  4646     // When scanning the RS, we only care about objs in CS.
  4647     if (barrier == G1BarrierRS) {
  4648       _par_scan_state->update_rs(_from, p, _worker_id);
  4649     } else if (barrier == G1BarrierKlass) {
  4650       do_klass_barrier(p, forwardee);
  4652   } else {
  4653     // The object is not in collection set. If we're a root scanning
  4654     // closure during an initial mark pause (i.e. do_mark_object will
  4655     // be true) then attempt to mark the object.
  4656     if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
  4657       mark_object(obj);
  4661   if (barrier == G1BarrierEvac && obj != NULL) {
  4662     _par_scan_state->update_rs(_from, p, _worker_id);
  4665   if (do_gen_barrier && obj != NULL) {
  4666     par_do_barrier(p);
  4670 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
  4671 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
  4673 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
  4674   assert(has_partial_array_mask(p), "invariant");
  4675   oop from_obj = clear_partial_array_mask(p);
  4677   assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
  4678   assert(from_obj->is_objArray(), "must be obj array");
  4679   objArrayOop from_obj_array = objArrayOop(from_obj);
  4680   // The from-space object contains the real length.
  4681   int length                 = from_obj_array->length();
  4683   assert(from_obj->is_forwarded(), "must be forwarded");
  4684   oop to_obj                 = from_obj->forwardee();
  4685   assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
  4686   objArrayOop to_obj_array   = objArrayOop(to_obj);
  4687   // We keep track of the next start index in the length field of the
  4688   // to-space object.
  4689   int next_index             = to_obj_array->length();
  4690   assert(0 <= next_index && next_index < length,
  4691          err_msg("invariant, next index: %d, length: %d", next_index, length));
  4693   int start                  = next_index;
  4694   int end                    = length;
  4695   int remainder              = end - start;
  4696   // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
  4697   if (remainder > 2 * ParGCArrayScanChunk) {
  4698     end = start + ParGCArrayScanChunk;
  4699     to_obj_array->set_length(end);
  4700     // Push the remainder before we process the range in case another
  4701     // worker has run out of things to do and can steal it.
  4702     oop* from_obj_p = set_partial_array_mask(from_obj);
  4703     _par_scan_state->push_on_queue(from_obj_p);
  4704   } else {
  4705     assert(length == end, "sanity");
  4706     // We'll process the final range for this object. Restore the length
  4707     // so that the heap remains parsable in case of evacuation failure.
  4708     to_obj_array->set_length(end);
  4710   _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
  4711   // Process indexes [start,end). It will also process the header
  4712   // along with the first chunk (i.e., the chunk with start == 0).
  4713   // Note that at this point the length field of to_obj_array is not
  4714   // correct given that we are using it to keep track of the next
  4715   // start index. oop_iterate_range() (thankfully!) ignores the length
  4716   // field and only relies on the start / end parameters.  It does
  4717   // however return the size of the object which will be incorrect. So
  4718   // we have to ignore it even if we wanted to use it.
  4719   to_obj_array->oop_iterate_range(&_scanner, start, end);
  4722 class G1ParEvacuateFollowersClosure : public VoidClosure {
  4723 protected:
  4724   G1CollectedHeap*              _g1h;
  4725   G1ParScanThreadState*         _par_scan_state;
  4726   RefToScanQueueSet*            _queues;
  4727   ParallelTaskTerminator*       _terminator;
  4729   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
  4730   RefToScanQueueSet*      queues()         { return _queues; }
  4731   ParallelTaskTerminator* terminator()     { return _terminator; }
  4733 public:
  4734   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
  4735                                 G1ParScanThreadState* par_scan_state,
  4736                                 RefToScanQueueSet* queues,
  4737                                 ParallelTaskTerminator* terminator)
  4738     : _g1h(g1h), _par_scan_state(par_scan_state),
  4739       _queues(queues), _terminator(terminator) {}
  4741   void do_void();
  4743 private:
  4744   inline bool offer_termination();
  4745 };
  4747 bool G1ParEvacuateFollowersClosure::offer_termination() {
  4748   G1ParScanThreadState* const pss = par_scan_state();
  4749   pss->start_term_time();
  4750   const bool res = terminator()->offer_termination();
  4751   pss->end_term_time();
  4752   return res;
  4755 void G1ParEvacuateFollowersClosure::do_void() {
  4756   StarTask stolen_task;
  4757   G1ParScanThreadState* const pss = par_scan_state();
  4758   pss->trim_queue();
  4760   do {
  4761     while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
  4762       assert(pss->verify_task(stolen_task), "sanity");
  4763       if (stolen_task.is_narrow()) {
  4764         pss->deal_with_reference((narrowOop*) stolen_task);
  4765       } else {
  4766         pss->deal_with_reference((oop*) stolen_task);
  4769       // We've just processed a reference and we might have made
  4770       // available new entries on the queues. So we have to make sure
  4771       // we drain the queues as necessary.
  4772       pss->trim_queue();
  4774   } while (!offer_termination());
  4776   pss->retire_alloc_buffers();
  4779 class G1KlassScanClosure : public KlassClosure {
  4780  G1ParCopyHelper* _closure;
  4781  bool             _process_only_dirty;
  4782  int              _count;
  4783  public:
  4784   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
  4785       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
  4786   void do_klass(Klass* klass) {
  4787     // If the klass has not been dirtied we know that there's
  4788     // no references into  the young gen and we can skip it.
  4789    if (!_process_only_dirty || klass->has_modified_oops()) {
  4790       // Clean the klass since we're going to scavenge all the metadata.
  4791       klass->clear_modified_oops();
  4793       // Tell the closure that this klass is the Klass to scavenge
  4794       // and is the one to dirty if oops are left pointing into the young gen.
  4795       _closure->set_scanned_klass(klass);
  4797       klass->oops_do(_closure);
  4799       _closure->set_scanned_klass(NULL);
  4801     _count++;
  4803 };
  4805 class G1ParTask : public AbstractGangTask {
  4806 protected:
  4807   G1CollectedHeap*       _g1h;
  4808   RefToScanQueueSet      *_queues;
  4809   ParallelTaskTerminator _terminator;
  4810   uint _n_workers;
  4812   Mutex _stats_lock;
  4813   Mutex* stats_lock() { return &_stats_lock; }
  4815   size_t getNCards() {
  4816     return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
  4817       / G1BlockOffsetSharedArray::N_bytes;
  4820 public:
  4821   G1ParTask(G1CollectedHeap* g1h,
  4822             RefToScanQueueSet *task_queues)
  4823     : AbstractGangTask("G1 collection"),
  4824       _g1h(g1h),
  4825       _queues(task_queues),
  4826       _terminator(0, _queues),
  4827       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
  4828   {}
  4830   RefToScanQueueSet* queues() { return _queues; }
  4832   RefToScanQueue *work_queue(int i) {
  4833     return queues()->queue(i);
  4836   ParallelTaskTerminator* terminator() { return &_terminator; }
  4838   virtual void set_for_termination(int active_workers) {
  4839     // This task calls set_n_termination() in par_non_clean_card_iterate_work()
  4840     // in the young space (_par_seq_tasks) in the G1 heap
  4841     // for SequentialSubTasksDone.
  4842     // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
  4843     // both of which need setting by set_n_termination().
  4844     _g1h->SharedHeap::set_n_termination(active_workers);
  4845     _g1h->set_n_termination(active_workers);
  4846     terminator()->reset_for_reuse(active_workers);
  4847     _n_workers = active_workers;
  4850   void work(uint worker_id) {
  4851     if (worker_id >= _n_workers) return;  // no work needed this round
  4853     double start_time_ms = os::elapsedTime() * 1000.0;
  4854     _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
  4857       ResourceMark rm;
  4858       HandleMark   hm;
  4860       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
  4862       G1ParScanThreadState            pss(_g1h, worker_id);
  4863       G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss, rp);
  4864       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
  4865       G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss, rp);
  4867       pss.set_evac_closure(&scan_evac_cl);
  4868       pss.set_evac_failure_closure(&evac_failure_cl);
  4869       pss.set_partial_scan_closure(&partial_scan_cl);
  4871       G1ParScanExtRootClosure        only_scan_root_cl(_g1h, &pss, rp);
  4872       G1ParScanMetadataClosure       only_scan_metadata_cl(_g1h, &pss, rp);
  4874       G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
  4875       G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp);
  4877       bool only_young                 = _g1h->g1_policy()->gcs_are_young();
  4878       G1KlassScanClosure              scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false);
  4879       G1KlassScanClosure              only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young);
  4881       OopClosure*                    scan_root_cl = &only_scan_root_cl;
  4882       G1KlassScanClosure*            scan_klasses_cl = &only_scan_klasses_cl_s;
  4884       if (_g1h->g1_policy()->during_initial_mark_pause()) {
  4885         // We also need to mark copied objects.
  4886         scan_root_cl = &scan_mark_root_cl;
  4887         scan_klasses_cl = &scan_mark_klasses_cl_s;
  4890       G1ParPushHeapRSClosure          push_heap_rs_cl(_g1h, &pss);
  4892       int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
  4894       pss.start_strong_roots();
  4895       _g1h->g1_process_strong_roots(/* is scavenging */ true,
  4896                                     SharedHeap::ScanningOption(so),
  4897                                     scan_root_cl,
  4898                                     &push_heap_rs_cl,
  4899                                     scan_klasses_cl,
  4900                                     worker_id);
  4901       pss.end_strong_roots();
  4904         double start = os::elapsedTime();
  4905         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
  4906         evac.do_void();
  4907         double elapsed_ms = (os::elapsedTime()-start)*1000.0;
  4908         double term_ms = pss.term_time()*1000.0;
  4909         _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
  4910         _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
  4912       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
  4913       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
  4915       if (ParallelGCVerbose) {
  4916         MutexLocker x(stats_lock());
  4917         pss.print_termination_stats(worker_id);
  4920       assert(pss.refs()->is_empty(), "should be empty");
  4922       // Close the inner scope so that the ResourceMark and HandleMark
  4923       // destructors are executed here and are included as part of the
  4924       // "GC Worker Time".
  4927     double end_time_ms = os::elapsedTime() * 1000.0;
  4928     _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
  4930 };
  4932 // *** Common G1 Evacuation Stuff
  4934 // Closures that support the filtering of CodeBlobs scanned during
  4935 // external root scanning.
  4937 // Closure applied to reference fields in code blobs (specifically nmethods)
  4938 // to determine whether an nmethod contains references that point into
  4939 // the collection set. Used as a predicate when walking code roots so
  4940 // that only nmethods that point into the collection set are added to the
  4941 // 'marked' list.
  4943 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure {
  4945   class G1PointsIntoCSOopClosure : public OopClosure {
  4946     G1CollectedHeap* _g1;
  4947     bool _points_into_cs;
  4948   public:
  4949     G1PointsIntoCSOopClosure(G1CollectedHeap* g1) :
  4950       _g1(g1), _points_into_cs(false) { }
  4952     bool points_into_cs() const { return _points_into_cs; }
  4954     template <class T>
  4955     void do_oop_nv(T* p) {
  4956       if (!_points_into_cs) {
  4957         T heap_oop = oopDesc::load_heap_oop(p);
  4958         if (!oopDesc::is_null(heap_oop) &&
  4959             _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) {
  4960           _points_into_cs = true;
  4965     virtual void do_oop(oop* p)        { do_oop_nv(p); }
  4966     virtual void do_oop(narrowOop* p)  { do_oop_nv(p); }
  4967   };
  4969   G1CollectedHeap* _g1;
  4971 public:
  4972   G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) :
  4973     CodeBlobToOopClosure(cl, true), _g1(g1) { }
  4975   virtual void do_code_blob(CodeBlob* cb) {
  4976     nmethod* nm = cb->as_nmethod_or_null();
  4977     if (nm != NULL && !(nm->test_oops_do_mark())) {
  4978       G1PointsIntoCSOopClosure predicate_cl(_g1);
  4979       nm->oops_do(&predicate_cl);
  4981       if (predicate_cl.points_into_cs()) {
  4982         // At least one of the reference fields or the oop relocations
  4983         // in the nmethod points into the collection set. We have to
  4984         // 'mark' this nmethod.
  4985         // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob()
  4986         // or MarkingCodeBlobClosure::do_code_blob() change.
  4987         if (!nm->test_set_oops_do_mark()) {
  4988           do_newly_marked_nmethod(nm);
  4993 };
  4995 // This method is run in a GC worker.
  4997 void
  4998 G1CollectedHeap::
  4999 g1_process_strong_roots(bool is_scavenging,
  5000                         ScanningOption so,
  5001                         OopClosure* scan_non_heap_roots,
  5002                         OopsInHeapRegionClosure* scan_rs,
  5003                         G1KlassScanClosure* scan_klasses,
  5004                         int worker_i) {
  5006   // First scan the strong roots
  5007   double ext_roots_start = os::elapsedTime();
  5008   double closure_app_time_sec = 0.0;
  5010   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
  5012   // Walk the code cache w/o buffering, because StarTask cannot handle
  5013   // unaligned oop locations.
  5014   G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots);
  5016   process_strong_roots(false, // no scoping; this is parallel code
  5017                        is_scavenging, so,
  5018                        &buf_scan_non_heap_roots,
  5019                        &eager_scan_code_roots,
  5020                        scan_klasses
  5021                        );
  5023   // Now the CM ref_processor roots.
  5024   if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
  5025     // We need to treat the discovered reference lists of the
  5026     // concurrent mark ref processor as roots and keep entries
  5027     // (which are added by the marking threads) on them live
  5028     // until they can be processed at the end of marking.
  5029     ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
  5032   // Finish up any enqueued closure apps (attributed as object copy time).
  5033   buf_scan_non_heap_roots.done();
  5035   double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds();
  5037   g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
  5039   double ext_root_time_ms =
  5040     ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
  5042   g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
  5044   // During conc marking we have to filter the per-thread SATB buffers
  5045   // to make sure we remove any oops into the CSet (which will show up
  5046   // as implicitly live).
  5047   double satb_filtering_ms = 0.0;
  5048   if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
  5049     if (mark_in_progress()) {
  5050       double satb_filter_start = os::elapsedTime();
  5052       JavaThread::satb_mark_queue_set().filter_thread_buffers();
  5054       satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
  5057   g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
  5059   // Now scan the complement of the collection set.
  5060   if (scan_rs != NULL) {
  5061     g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
  5063   _process_strong_tasks->all_tasks_completed();
  5066 void
  5067 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
  5068                                        OopClosure* non_root_closure) {
  5069   CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
  5070   SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
  5073 // Weak Reference Processing support
  5075 // An always "is_alive" closure that is used to preserve referents.
  5076 // If the object is non-null then it's alive.  Used in the preservation
  5077 // of referent objects that are pointed to by reference objects
  5078 // discovered by the CM ref processor.
  5079 class G1AlwaysAliveClosure: public BoolObjectClosure {
  5080   G1CollectedHeap* _g1;
  5081 public:
  5082   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
  5083   void do_object(oop p) { assert(false, "Do not call."); }
  5084   bool do_object_b(oop p) {
  5085     if (p != NULL) {
  5086       return true;
  5088     return false;
  5090 };
  5092 bool G1STWIsAliveClosure::do_object_b(oop p) {
  5093   // An object is reachable if it is outside the collection set,
  5094   // or is inside and copied.
  5095   return !_g1->obj_in_cs(p) || p->is_forwarded();
  5098 // Non Copying Keep Alive closure
  5099 class G1KeepAliveClosure: public OopClosure {
  5100   G1CollectedHeap* _g1;
  5101 public:
  5102   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
  5103   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
  5104   void do_oop(      oop* p) {
  5105     oop obj = *p;
  5107     if (_g1->obj_in_cs(obj)) {
  5108       assert( obj->is_forwarded(), "invariant" );
  5109       *p = obj->forwardee();
  5112 };
  5114 // Copying Keep Alive closure - can be called from both
  5115 // serial and parallel code as long as different worker
  5116 // threads utilize different G1ParScanThreadState instances
  5117 // and different queues.
  5119 class G1CopyingKeepAliveClosure: public OopClosure {
  5120   G1CollectedHeap*         _g1h;
  5121   OopClosure*              _copy_non_heap_obj_cl;
  5122   OopsInHeapRegionClosure* _copy_metadata_obj_cl;
  5123   G1ParScanThreadState*    _par_scan_state;
  5125 public:
  5126   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
  5127                             OopClosure* non_heap_obj_cl,
  5128                             OopsInHeapRegionClosure* metadata_obj_cl,
  5129                             G1ParScanThreadState* pss):
  5130     _g1h(g1h),
  5131     _copy_non_heap_obj_cl(non_heap_obj_cl),
  5132     _copy_metadata_obj_cl(metadata_obj_cl),
  5133     _par_scan_state(pss)
  5134   {}
  5136   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
  5137   virtual void do_oop(      oop* p) { do_oop_work(p); }
  5139   template <class T> void do_oop_work(T* p) {
  5140     oop obj = oopDesc::load_decode_heap_oop(p);
  5142     if (_g1h->obj_in_cs(obj)) {
  5143       // If the referent object has been forwarded (either copied
  5144       // to a new location or to itself in the event of an
  5145       // evacuation failure) then we need to update the reference
  5146       // field and, if both reference and referent are in the G1
  5147       // heap, update the RSet for the referent.
  5148       //
  5149       // If the referent has not been forwarded then we have to keep
  5150       // it alive by policy. Therefore we have copy the referent.
  5151       //
  5152       // If the reference field is in the G1 heap then we can push
  5153       // on the PSS queue. When the queue is drained (after each
  5154       // phase of reference processing) the object and it's followers
  5155       // will be copied, the reference field set to point to the
  5156       // new location, and the RSet updated. Otherwise we need to
  5157       // use the the non-heap or metadata closures directly to copy
  5158       // the refernt object and update the pointer, while avoiding
  5159       // updating the RSet.
  5161       if (_g1h->is_in_g1_reserved(p)) {
  5162         _par_scan_state->push_on_queue(p);
  5163       } else {
  5164         assert(!ClassLoaderDataGraph::contains((address)p),
  5165                err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) "
  5166                               PTR_FORMAT, p));
  5167           _copy_non_heap_obj_cl->do_oop(p);
  5171 };
  5173 // Serial drain queue closure. Called as the 'complete_gc'
  5174 // closure for each discovered list in some of the
  5175 // reference processing phases.
  5177 class G1STWDrainQueueClosure: public VoidClosure {
  5178 protected:
  5179   G1CollectedHeap* _g1h;
  5180   G1ParScanThreadState* _par_scan_state;
  5182   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
  5184 public:
  5185   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
  5186     _g1h(g1h),
  5187     _par_scan_state(pss)
  5188   { }
  5190   void do_void() {
  5191     G1ParScanThreadState* const pss = par_scan_state();
  5192     pss->trim_queue();
  5194 };
  5196 // Parallel Reference Processing closures
  5198 // Implementation of AbstractRefProcTaskExecutor for parallel reference
  5199 // processing during G1 evacuation pauses.
  5201 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
  5202 private:
  5203   G1CollectedHeap*   _g1h;
  5204   RefToScanQueueSet* _queues;
  5205   FlexibleWorkGang*  _workers;
  5206   int                _active_workers;
  5208 public:
  5209   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
  5210                         FlexibleWorkGang* workers,
  5211                         RefToScanQueueSet *task_queues,
  5212                         int n_workers) :
  5213     _g1h(g1h),
  5214     _queues(task_queues),
  5215     _workers(workers),
  5216     _active_workers(n_workers)
  5218     assert(n_workers > 0, "shouldn't call this otherwise");
  5221   // Executes the given task using concurrent marking worker threads.
  5222   virtual void execute(ProcessTask& task);
  5223   virtual void execute(EnqueueTask& task);
  5224 };
  5226 // Gang task for possibly parallel reference processing
  5228 class G1STWRefProcTaskProxy: public AbstractGangTask {
  5229   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
  5230   ProcessTask&     _proc_task;
  5231   G1CollectedHeap* _g1h;
  5232   RefToScanQueueSet *_task_queues;
  5233   ParallelTaskTerminator* _terminator;
  5235 public:
  5236   G1STWRefProcTaskProxy(ProcessTask& proc_task,
  5237                      G1CollectedHeap* g1h,
  5238                      RefToScanQueueSet *task_queues,
  5239                      ParallelTaskTerminator* terminator) :
  5240     AbstractGangTask("Process reference objects in parallel"),
  5241     _proc_task(proc_task),
  5242     _g1h(g1h),
  5243     _task_queues(task_queues),
  5244     _terminator(terminator)
  5245   {}
  5247   virtual void work(uint worker_id) {
  5248     // The reference processing task executed by a single worker.
  5249     ResourceMark rm;
  5250     HandleMark   hm;
  5252     G1STWIsAliveClosure is_alive(_g1h);
  5254     G1ParScanThreadState pss(_g1h, worker_id);
  5256     G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss, NULL);
  5257     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
  5258     G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss, NULL);
  5260     pss.set_evac_closure(&scan_evac_cl);
  5261     pss.set_evac_failure_closure(&evac_failure_cl);
  5262     pss.set_partial_scan_closure(&partial_scan_cl);
  5264     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
  5265     G1ParScanMetadataClosure       only_copy_metadata_cl(_g1h, &pss, NULL);
  5267     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
  5268     G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
  5270     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
  5271     OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
  5273     if (_g1h->g1_policy()->during_initial_mark_pause()) {
  5274       // We also need to mark copied objects.
  5275       copy_non_heap_cl = &copy_mark_non_heap_cl;
  5276       copy_metadata_cl = &copy_mark_metadata_cl;
  5279     // Keep alive closure.
  5280     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
  5282     // Complete GC closure
  5283     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
  5285     // Call the reference processing task's work routine.
  5286     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
  5288     // Note we cannot assert that the refs array is empty here as not all
  5289     // of the processing tasks (specifically phase2 - pp2_work) execute
  5290     // the complete_gc closure (which ordinarily would drain the queue) so
  5291     // the queue may not be empty.
  5293 };
  5295 // Driver routine for parallel reference processing.
  5296 // Creates an instance of the ref processing gang
  5297 // task and has the worker threads execute it.
  5298 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
  5299   assert(_workers != NULL, "Need parallel worker threads.");
  5301   ParallelTaskTerminator terminator(_active_workers, _queues);
  5302   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
  5304   _g1h->set_par_threads(_active_workers);
  5305   _workers->run_task(&proc_task_proxy);
  5306   _g1h->set_par_threads(0);
  5309 // Gang task for parallel reference enqueueing.
  5311 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
  5312   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
  5313   EnqueueTask& _enq_task;
  5315 public:
  5316   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
  5317     AbstractGangTask("Enqueue reference objects in parallel"),
  5318     _enq_task(enq_task)
  5319   { }
  5321   virtual void work(uint worker_id) {
  5322     _enq_task.work(worker_id);
  5324 };
  5326 // Driver routine for parallel reference enqueing.
  5327 // Creates an instance of the ref enqueueing gang
  5328 // task and has the worker threads execute it.
  5330 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
  5331   assert(_workers != NULL, "Need parallel worker threads.");
  5333   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
  5335   _g1h->set_par_threads(_active_workers);
  5336   _workers->run_task(&enq_task_proxy);
  5337   _g1h->set_par_threads(0);
  5340 // End of weak reference support closures
  5342 // Abstract task used to preserve (i.e. copy) any referent objects
  5343 // that are in the collection set and are pointed to by reference
  5344 // objects discovered by the CM ref processor.
  5346 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
  5347 protected:
  5348   G1CollectedHeap* _g1h;
  5349   RefToScanQueueSet      *_queues;
  5350   ParallelTaskTerminator _terminator;
  5351   uint _n_workers;
  5353 public:
  5354   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
  5355     AbstractGangTask("ParPreserveCMReferents"),
  5356     _g1h(g1h),
  5357     _queues(task_queues),
  5358     _terminator(workers, _queues),
  5359     _n_workers(workers)
  5360   { }
  5362   void work(uint worker_id) {
  5363     ResourceMark rm;
  5364     HandleMark   hm;
  5366     G1ParScanThreadState            pss(_g1h, worker_id);
  5367     G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss, NULL);
  5368     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
  5369     G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss, NULL);
  5371     pss.set_evac_closure(&scan_evac_cl);
  5372     pss.set_evac_failure_closure(&evac_failure_cl);
  5373     pss.set_partial_scan_closure(&partial_scan_cl);
  5375     assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
  5378     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
  5379     G1ParScanMetadataClosure       only_copy_metadata_cl(_g1h, &pss, NULL);
  5381     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
  5382     G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
  5384     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
  5385     OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
  5387     if (_g1h->g1_policy()->during_initial_mark_pause()) {
  5388       // We also need to mark copied objects.
  5389       copy_non_heap_cl = &copy_mark_non_heap_cl;
  5390       copy_metadata_cl = &copy_mark_metadata_cl;
  5393     // Is alive closure
  5394     G1AlwaysAliveClosure always_alive(_g1h);
  5396     // Copying keep alive closure. Applied to referent objects that need
  5397     // to be copied.
  5398     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
  5400     ReferenceProcessor* rp = _g1h->ref_processor_cm();
  5402     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
  5403     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
  5405     // limit is set using max_num_q() - which was set using ParallelGCThreads.
  5406     // So this must be true - but assert just in case someone decides to
  5407     // change the worker ids.
  5408     assert(0 <= worker_id && worker_id < limit, "sanity");
  5409     assert(!rp->discovery_is_atomic(), "check this code");
  5411     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
  5412     for (uint idx = worker_id; idx < limit; idx += stride) {
  5413       DiscoveredList& ref_list = rp->discovered_refs()[idx];
  5415       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
  5416       while (iter.has_next()) {
  5417         // Since discovery is not atomic for the CM ref processor, we
  5418         // can see some null referent objects.
  5419         iter.load_ptrs(DEBUG_ONLY(true));
  5420         oop ref = iter.obj();
  5422         // This will filter nulls.
  5423         if (iter.is_referent_alive()) {
  5424           iter.make_referent_alive();
  5426         iter.move_to_next();
  5430     // Drain the queue - which may cause stealing
  5431     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
  5432     drain_queue.do_void();
  5433     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
  5434     assert(pss.refs()->is_empty(), "should be");
  5436 };
  5438 // Weak Reference processing during an evacuation pause (part 1).
  5439 void G1CollectedHeap::process_discovered_references() {
  5440   double ref_proc_start = os::elapsedTime();
  5442   ReferenceProcessor* rp = _ref_processor_stw;
  5443   assert(rp->discovery_enabled(), "should have been enabled");
  5445   // Any reference objects, in the collection set, that were 'discovered'
  5446   // by the CM ref processor should have already been copied (either by
  5447   // applying the external root copy closure to the discovered lists, or
  5448   // by following an RSet entry).
  5449   //
  5450   // But some of the referents, that are in the collection set, that these
  5451   // reference objects point to may not have been copied: the STW ref
  5452   // processor would have seen that the reference object had already
  5453   // been 'discovered' and would have skipped discovering the reference,
  5454   // but would not have treated the reference object as a regular oop.
  5455   // As a reult the copy closure would not have been applied to the
  5456   // referent object.
  5457   //
  5458   // We need to explicitly copy these referent objects - the references
  5459   // will be processed at the end of remarking.
  5460   //
  5461   // We also need to do this copying before we process the reference
  5462   // objects discovered by the STW ref processor in case one of these
  5463   // referents points to another object which is also referenced by an
  5464   // object discovered by the STW ref processor.
  5466   uint active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
  5467                         workers()->active_workers() : 1);
  5469   assert(!G1CollectedHeap::use_parallel_gc_threads() ||
  5470            active_workers == workers()->active_workers(),
  5471            "Need to reset active_workers");
  5473   set_par_threads(active_workers);
  5474   G1ParPreserveCMReferentsTask keep_cm_referents(this, active_workers, _task_queues);
  5476   if (G1CollectedHeap::use_parallel_gc_threads()) {
  5477     workers()->run_task(&keep_cm_referents);
  5478   } else {
  5479     keep_cm_referents.work(0);
  5482   set_par_threads(0);
  5484   // Closure to test whether a referent is alive.
  5485   G1STWIsAliveClosure is_alive(this);
  5487   // Even when parallel reference processing is enabled, the processing
  5488   // of JNI refs is serial and performed serially by the current thread
  5489   // rather than by a worker. The following PSS will be used for processing
  5490   // JNI refs.
  5492   // Use only a single queue for this PSS.
  5493   G1ParScanThreadState pss(this, 0);
  5495   // We do not embed a reference processor in the copying/scanning
  5496   // closures while we're actually processing the discovered
  5497   // reference objects.
  5498   G1ParScanHeapEvacClosure        scan_evac_cl(this, &pss, NULL);
  5499   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
  5500   G1ParScanPartialArrayClosure    partial_scan_cl(this, &pss, NULL);
  5502   pss.set_evac_closure(&scan_evac_cl);
  5503   pss.set_evac_failure_closure(&evac_failure_cl);
  5504   pss.set_partial_scan_closure(&partial_scan_cl);
  5506   assert(pss.refs()->is_empty(), "pre-condition");
  5508   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
  5509   G1ParScanMetadataClosure       only_copy_metadata_cl(this, &pss, NULL);
  5511   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
  5512   G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL);
  5514   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
  5515   OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
  5517   if (_g1h->g1_policy()->during_initial_mark_pause()) {
  5518     // We also need to mark copied objects.
  5519     copy_non_heap_cl = &copy_mark_non_heap_cl;
  5520     copy_metadata_cl = &copy_mark_metadata_cl;
  5523   // Keep alive closure.
  5524   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss);
  5526   // Serial Complete GC closure
  5527   G1STWDrainQueueClosure drain_queue(this, &pss);
  5529   // Setup the soft refs policy...
  5530   rp->setup_policy(false);
  5532   if (!rp->processing_is_mt()) {
  5533     // Serial reference processing...
  5534     rp->process_discovered_references(&is_alive,
  5535                                       &keep_alive,
  5536                                       &drain_queue,
  5537                                       NULL);
  5538   } else {
  5539     // Parallel reference processing
  5540     assert(rp->num_q() == active_workers, "sanity");
  5541     assert(active_workers <= rp->max_num_q(), "sanity");
  5543     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
  5544     rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor);
  5547   // We have completed copying any necessary live referent objects
  5548   // (that were not copied during the actual pause) so we can
  5549   // retire any active alloc buffers
  5550   pss.retire_alloc_buffers();
  5551   assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
  5553   double ref_proc_time = os::elapsedTime() - ref_proc_start;
  5554   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
  5557 // Weak Reference processing during an evacuation pause (part 2).
  5558 void G1CollectedHeap::enqueue_discovered_references() {
  5559   double ref_enq_start = os::elapsedTime();
  5561   ReferenceProcessor* rp = _ref_processor_stw;
  5562   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
  5564   // Now enqueue any remaining on the discovered lists on to
  5565   // the pending list.
  5566   if (!rp->processing_is_mt()) {
  5567     // Serial reference processing...
  5568     rp->enqueue_discovered_references();
  5569   } else {
  5570     // Parallel reference enqueuing
  5572     uint active_workers = (ParallelGCThreads > 0 ? workers()->active_workers() : 1);
  5573     assert(active_workers == workers()->active_workers(),
  5574            "Need to reset active_workers");
  5575     assert(rp->num_q() == active_workers, "sanity");
  5576     assert(active_workers <= rp->max_num_q(), "sanity");
  5578     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
  5579     rp->enqueue_discovered_references(&par_task_executor);
  5582   rp->verify_no_references_recorded();
  5583   assert(!rp->discovery_enabled(), "should have been disabled");
  5585   // FIXME
  5586   // CM's reference processing also cleans up the string and symbol tables.
  5587   // Should we do that here also? We could, but it is a serial operation
  5588   // and could signicantly increase the pause time.
  5590   double ref_enq_time = os::elapsedTime() - ref_enq_start;
  5591   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
  5594 void G1CollectedHeap::evacuate_collection_set() {
  5595   _expand_heap_after_alloc_failure = true;
  5596   set_evacuation_failed(false);
  5598   // Should G1EvacuationFailureALot be in effect for this GC?
  5599   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
  5601   g1_rem_set()->prepare_for_oops_into_collection_set_do();
  5602   concurrent_g1_refine()->set_use_cache(false);
  5603   concurrent_g1_refine()->clear_hot_cache_claimed_index();
  5605   uint n_workers;
  5606   if (G1CollectedHeap::use_parallel_gc_threads()) {
  5607     n_workers =
  5608       AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
  5609                                      workers()->active_workers(),
  5610                                      Threads::number_of_non_daemon_threads());
  5611     assert(UseDynamicNumberOfGCThreads ||
  5612            n_workers == workers()->total_workers(),
  5613            "If not dynamic should be using all the  workers");
  5614     workers()->set_active_workers(n_workers);
  5615     set_par_threads(n_workers);
  5616   } else {
  5617     assert(n_par_threads() == 0,
  5618            "Should be the original non-parallel value");
  5619     n_workers = 1;
  5622   G1ParTask g1_par_task(this, _task_queues);
  5624   init_for_evac_failure(NULL);
  5626   rem_set()->prepare_for_younger_refs_iterate(true);
  5628   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
  5629   double start_par_time_sec = os::elapsedTime();
  5630   double end_par_time_sec;
  5633     StrongRootsScope srs(this);
  5635     if (G1CollectedHeap::use_parallel_gc_threads()) {
  5636       // The individual threads will set their evac-failure closures.
  5637       if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
  5638       // These tasks use ShareHeap::_process_strong_tasks
  5639       assert(UseDynamicNumberOfGCThreads ||
  5640              workers()->active_workers() == workers()->total_workers(),
  5641              "If not dynamic should be using all the  workers");
  5642       workers()->run_task(&g1_par_task);
  5643     } else {
  5644       g1_par_task.set_for_termination(n_workers);
  5645       g1_par_task.work(0);
  5647     end_par_time_sec = os::elapsedTime();
  5649     // Closing the inner scope will execute the destructor
  5650     // for the StrongRootsScope object. We record the current
  5651     // elapsed time before closing the scope so that time
  5652     // taken for the SRS destructor is NOT included in the
  5653     // reported parallel time.
  5656   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
  5657   g1_policy()->phase_times()->record_par_time(par_time_ms);
  5659   double code_root_fixup_time_ms =
  5660         (os::elapsedTime() - end_par_time_sec) * 1000.0;
  5661   g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
  5663   set_par_threads(0);
  5665   // Process any discovered reference objects - we have
  5666   // to do this _before_ we retire the GC alloc regions
  5667   // as we may have to copy some 'reachable' referent
  5668   // objects (and their reachable sub-graphs) that were
  5669   // not copied during the pause.
  5670   process_discovered_references();
  5672   // Weak root processing.
  5673   // Note: when JSR 292 is enabled and code blobs can contain
  5674   // non-perm oops then we will need to process the code blobs
  5675   // here too.
  5677     G1STWIsAliveClosure is_alive(this);
  5678     G1KeepAliveClosure keep_alive(this);
  5679     JNIHandles::weak_oops_do(&is_alive, &keep_alive);
  5682   release_gc_alloc_regions();
  5683   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
  5685   concurrent_g1_refine()->clear_hot_cache();
  5686   concurrent_g1_refine()->set_use_cache(true);
  5688   finalize_for_evac_failure();
  5690   if (evacuation_failed()) {
  5691     remove_self_forwarding_pointers();
  5693     // Reset the G1EvacuationFailureALot counters and flags
  5694     // Note: the values are reset only when an actual
  5695     // evacuation failure occurs.
  5696     NOT_PRODUCT(reset_evacuation_should_fail();)
  5699   // Enqueue any remaining references remaining on the STW
  5700   // reference processor's discovered lists. We need to do
  5701   // this after the card table is cleaned (and verified) as
  5702   // the act of enqueuing entries on to the pending list
  5703   // will log these updates (and dirty their associated
  5704   // cards). We need these updates logged to update any
  5705   // RSets.
  5706   enqueue_discovered_references();
  5708   if (G1DeferredRSUpdate) {
  5709     RedirtyLoggedCardTableEntryFastClosure redirty;
  5710     dirty_card_queue_set().set_closure(&redirty);
  5711     dirty_card_queue_set().apply_closure_to_all_completed_buffers();
  5713     DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
  5714     dcq.merge_bufferlists(&dirty_card_queue_set());
  5715     assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
  5717   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
  5720 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
  5721                                      size_t* pre_used,
  5722                                      FreeRegionList* free_list,
  5723                                      OldRegionSet* old_proxy_set,
  5724                                      HumongousRegionSet* humongous_proxy_set,
  5725                                      HRRSCleanupTask* hrrs_cleanup_task,
  5726                                      bool par) {
  5727   if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
  5728     if (hr->isHumongous()) {
  5729       assert(hr->startsHumongous(), "we should only see starts humongous");
  5730       free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
  5731     } else {
  5732       _old_set.remove_with_proxy(hr, old_proxy_set);
  5733       free_region(hr, pre_used, free_list, par);
  5735   } else {
  5736     hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
  5740 void G1CollectedHeap::free_region(HeapRegion* hr,
  5741                                   size_t* pre_used,
  5742                                   FreeRegionList* free_list,
  5743                                   bool par) {
  5744   assert(!hr->isHumongous(), "this is only for non-humongous regions");
  5745   assert(!hr->is_empty(), "the region should not be empty");
  5746   assert(free_list != NULL, "pre-condition");
  5748   *pre_used += hr->used();
  5749   hr->hr_clear(par, true /* clear_space */);
  5750   free_list->add_as_head(hr);
  5753 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
  5754                                      size_t* pre_used,
  5755                                      FreeRegionList* free_list,
  5756                                      HumongousRegionSet* humongous_proxy_set,
  5757                                      bool par) {
  5758   assert(hr->startsHumongous(), "this is only for starts humongous regions");
  5759   assert(free_list != NULL, "pre-condition");
  5760   assert(humongous_proxy_set != NULL, "pre-condition");
  5762   size_t hr_used = hr->used();
  5763   size_t hr_capacity = hr->capacity();
  5764   size_t hr_pre_used = 0;
  5765   _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
  5766   // We need to read this before we make the region non-humongous,
  5767   // otherwise the information will be gone.
  5768   uint last_index = hr->last_hc_index();
  5769   hr->set_notHumongous();
  5770   free_region(hr, &hr_pre_used, free_list, par);
  5772   uint i = hr->hrs_index() + 1;
  5773   while (i < last_index) {
  5774     HeapRegion* curr_hr = region_at(i);
  5775     assert(curr_hr->continuesHumongous(), "invariant");
  5776     curr_hr->set_notHumongous();
  5777     free_region(curr_hr, &hr_pre_used, free_list, par);
  5778     i += 1;
  5780   assert(hr_pre_used == hr_used,
  5781          err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
  5782                  "should be the same", hr_pre_used, hr_used));
  5783   *pre_used += hr_pre_used;
  5786 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
  5787                                        FreeRegionList* free_list,
  5788                                        OldRegionSet* old_proxy_set,
  5789                                        HumongousRegionSet* humongous_proxy_set,
  5790                                        bool par) {
  5791   if (pre_used > 0) {
  5792     Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
  5793     MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
  5794     assert(_summary_bytes_used >= pre_used,
  5795            err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
  5796                    "should be >= pre_used: "SIZE_FORMAT,
  5797                    _summary_bytes_used, pre_used));
  5798     _summary_bytes_used -= pre_used;
  5800   if (free_list != NULL && !free_list->is_empty()) {
  5801     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
  5802     _free_list.add_as_head(free_list);
  5804   if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
  5805     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
  5806     _old_set.update_from_proxy(old_proxy_set);
  5808   if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
  5809     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
  5810     _humongous_set.update_from_proxy(humongous_proxy_set);
  5814 class G1ParCleanupCTTask : public AbstractGangTask {
  5815   CardTableModRefBS* _ct_bs;
  5816   G1CollectedHeap* _g1h;
  5817   HeapRegion* volatile _su_head;
  5818 public:
  5819   G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
  5820                      G1CollectedHeap* g1h) :
  5821     AbstractGangTask("G1 Par Cleanup CT Task"),
  5822     _ct_bs(ct_bs), _g1h(g1h) { }
  5824   void work(uint worker_id) {
  5825     HeapRegion* r;
  5826     while (r = _g1h->pop_dirty_cards_region()) {
  5827       clear_cards(r);
  5831   void clear_cards(HeapRegion* r) {
  5832     // Cards of the survivors should have already been dirtied.
  5833     if (!r->is_survivor()) {
  5834       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
  5837 };
  5839 #ifndef PRODUCT
  5840 class G1VerifyCardTableCleanup: public HeapRegionClosure {
  5841   G1CollectedHeap* _g1h;
  5842   CardTableModRefBS* _ct_bs;
  5843 public:
  5844   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
  5845     : _g1h(g1h), _ct_bs(ct_bs) { }
  5846   virtual bool doHeapRegion(HeapRegion* r) {
  5847     if (r->is_survivor()) {
  5848       _g1h->verify_dirty_region(r);
  5849     } else {
  5850       _g1h->verify_not_dirty_region(r);
  5852     return false;
  5854 };
  5856 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
  5857   // All of the region should be clean.
  5858   CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
  5859   MemRegion mr(hr->bottom(), hr->end());
  5860   ct_bs->verify_not_dirty_region(mr);
  5863 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
  5864   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
  5865   // dirty allocated blocks as they allocate them. The thread that
  5866   // retires each region and replaces it with a new one will do a
  5867   // maximal allocation to fill in [pre_dummy_top(),end()] but will
  5868   // not dirty that area (one less thing to have to do while holding
  5869   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
  5870   // is dirty.
  5871   CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
  5872   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
  5873   ct_bs->verify_dirty_region(mr);
  5876 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
  5877   CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
  5878   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
  5879     verify_dirty_region(hr);
  5883 void G1CollectedHeap::verify_dirty_young_regions() {
  5884   verify_dirty_young_list(_young_list->first_region());
  5886 #endif
  5888 void G1CollectedHeap::cleanUpCardTable() {
  5889   CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
  5890   double start = os::elapsedTime();
  5893     // Iterate over the dirty cards region list.
  5894     G1ParCleanupCTTask cleanup_task(ct_bs, this);
  5896     if (G1CollectedHeap::use_parallel_gc_threads()) {
  5897       set_par_threads();
  5898       workers()->run_task(&cleanup_task);
  5899       set_par_threads(0);
  5900     } else {
  5901       while (_dirty_cards_region_list) {
  5902         HeapRegion* r = _dirty_cards_region_list;
  5903         cleanup_task.clear_cards(r);
  5904         _dirty_cards_region_list = r->get_next_dirty_cards_region();
  5905         if (_dirty_cards_region_list == r) {
  5906           // The last region.
  5907           _dirty_cards_region_list = NULL;
  5909         r->set_next_dirty_cards_region(NULL);
  5912 #ifndef PRODUCT
  5913     if (G1VerifyCTCleanup || VerifyAfterGC) {
  5914       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
  5915       heap_region_iterate(&cleanup_verifier);
  5917 #endif
  5920   double elapsed = os::elapsedTime() - start;
  5921   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
  5924 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
  5925   size_t pre_used = 0;
  5926   FreeRegionList local_free_list("Local List for CSet Freeing");
  5928   double young_time_ms     = 0.0;
  5929   double non_young_time_ms = 0.0;
  5931   // Since the collection set is a superset of the the young list,
  5932   // all we need to do to clear the young list is clear its
  5933   // head and length, and unlink any young regions in the code below
  5934   _young_list->clear();
  5936   G1CollectorPolicy* policy = g1_policy();
  5938   double start_sec = os::elapsedTime();
  5939   bool non_young = true;
  5941   HeapRegion* cur = cs_head;
  5942   int age_bound = -1;
  5943   size_t rs_lengths = 0;
  5945   while (cur != NULL) {
  5946     assert(!is_on_master_free_list(cur), "sanity");
  5947     if (non_young) {
  5948       if (cur->is_young()) {
  5949         double end_sec = os::elapsedTime();
  5950         double elapsed_ms = (end_sec - start_sec) * 1000.0;
  5951         non_young_time_ms += elapsed_ms;
  5953         start_sec = os::elapsedTime();
  5954         non_young = false;
  5956     } else {
  5957       if (!cur->is_young()) {
  5958         double end_sec = os::elapsedTime();
  5959         double elapsed_ms = (end_sec - start_sec) * 1000.0;
  5960         young_time_ms += elapsed_ms;
  5962         start_sec = os::elapsedTime();
  5963         non_young = true;
  5967     rs_lengths += cur->rem_set()->occupied();
  5969     HeapRegion* next = cur->next_in_collection_set();
  5970     assert(cur->in_collection_set(), "bad CS");
  5971     cur->set_next_in_collection_set(NULL);
  5972     cur->set_in_collection_set(false);
  5974     if (cur->is_young()) {
  5975       int index = cur->young_index_in_cset();
  5976       assert(index != -1, "invariant");
  5977       assert((uint) index < policy->young_cset_region_length(), "invariant");
  5978       size_t words_survived = _surviving_young_words[index];
  5979       cur->record_surv_words_in_group(words_survived);
  5981       // At this point the we have 'popped' cur from the collection set
  5982       // (linked via next_in_collection_set()) but it is still in the
  5983       // young list (linked via next_young_region()). Clear the
  5984       // _next_young_region field.
  5985       cur->set_next_young_region(NULL);
  5986     } else {
  5987       int index = cur->young_index_in_cset();
  5988       assert(index == -1, "invariant");
  5991     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
  5992             (!cur->is_young() && cur->young_index_in_cset() == -1),
  5993             "invariant" );
  5995     if (!cur->evacuation_failed()) {
  5996       MemRegion used_mr = cur->used_region();
  5998       // And the region is empty.
  5999       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
  6000       free_region(cur, &pre_used, &local_free_list, false /* par */);
  6001     } else {
  6002       cur->uninstall_surv_rate_group();
  6003       if (cur->is_young()) {
  6004         cur->set_young_index_in_cset(-1);
  6006       cur->set_not_young();
  6007       cur->set_evacuation_failed(false);
  6008       // The region is now considered to be old.
  6009       _old_set.add(cur);
  6011     cur = next;
  6014   policy->record_max_rs_lengths(rs_lengths);
  6015   policy->cset_regions_freed();
  6017   double end_sec = os::elapsedTime();
  6018   double elapsed_ms = (end_sec - start_sec) * 1000.0;
  6020   if (non_young) {
  6021     non_young_time_ms += elapsed_ms;
  6022   } else {
  6023     young_time_ms += elapsed_ms;
  6026   update_sets_after_freeing_regions(pre_used, &local_free_list,
  6027                                     NULL /* old_proxy_set */,
  6028                                     NULL /* humongous_proxy_set */,
  6029                                     false /* par */);
  6030   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
  6031   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
  6034 // This routine is similar to the above but does not record
  6035 // any policy statistics or update free lists; we are abandoning
  6036 // the current incremental collection set in preparation of a
  6037 // full collection. After the full GC we will start to build up
  6038 // the incremental collection set again.
  6039 // This is only called when we're doing a full collection
  6040 // and is immediately followed by the tearing down of the young list.
  6042 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
  6043   HeapRegion* cur = cs_head;
  6045   while (cur != NULL) {
  6046     HeapRegion* next = cur->next_in_collection_set();
  6047     assert(cur->in_collection_set(), "bad CS");
  6048     cur->set_next_in_collection_set(NULL);
  6049     cur->set_in_collection_set(false);
  6050     cur->set_young_index_in_cset(-1);
  6051     cur = next;
  6055 void G1CollectedHeap::set_free_regions_coming() {
  6056   if (G1ConcRegionFreeingVerbose) {
  6057     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
  6058                            "setting free regions coming");
  6061   assert(!free_regions_coming(), "pre-condition");
  6062   _free_regions_coming = true;
  6065 void G1CollectedHeap::reset_free_regions_coming() {
  6066   assert(free_regions_coming(), "pre-condition");
  6069     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
  6070     _free_regions_coming = false;
  6071     SecondaryFreeList_lock->notify_all();
  6074   if (G1ConcRegionFreeingVerbose) {
  6075     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
  6076                            "reset free regions coming");
  6080 void G1CollectedHeap::wait_while_free_regions_coming() {
  6081   // Most of the time we won't have to wait, so let's do a quick test
  6082   // first before we take the lock.
  6083   if (!free_regions_coming()) {
  6084     return;
  6087   if (G1ConcRegionFreeingVerbose) {
  6088     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
  6089                            "waiting for free regions");
  6093     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
  6094     while (free_regions_coming()) {
  6095       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
  6099   if (G1ConcRegionFreeingVerbose) {
  6100     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
  6101                            "done waiting for free regions");
  6105 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
  6106   assert(heap_lock_held_for_gc(),
  6107               "the heap lock should already be held by or for this thread");
  6108   _young_list->push_region(hr);
  6111 class NoYoungRegionsClosure: public HeapRegionClosure {
  6112 private:
  6113   bool _success;
  6114 public:
  6115   NoYoungRegionsClosure() : _success(true) { }
  6116   bool doHeapRegion(HeapRegion* r) {
  6117     if (r->is_young()) {
  6118       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
  6119                              r->bottom(), r->end());
  6120       _success = false;
  6122     return false;
  6124   bool success() { return _success; }
  6125 };
  6127 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
  6128   bool ret = _young_list->check_list_empty(check_sample);
  6130   if (check_heap) {
  6131     NoYoungRegionsClosure closure;
  6132     heap_region_iterate(&closure);
  6133     ret = ret && closure.success();
  6136   return ret;
  6139 class TearDownRegionSetsClosure : public HeapRegionClosure {
  6140 private:
  6141   OldRegionSet *_old_set;
  6143 public:
  6144   TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
  6146   bool doHeapRegion(HeapRegion* r) {
  6147     if (r->is_empty()) {
  6148       // We ignore empty regions, we'll empty the free list afterwards
  6149     } else if (r->is_young()) {
  6150       // We ignore young regions, we'll empty the young list afterwards
  6151     } else if (r->isHumongous()) {
  6152       // We ignore humongous regions, we're not tearing down the
  6153       // humongous region set
  6154     } else {
  6155       // The rest should be old
  6156       _old_set->remove(r);
  6158     return false;
  6161   ~TearDownRegionSetsClosure() {
  6162     assert(_old_set->is_empty(), "post-condition");
  6164 };
  6166 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
  6167   assert_at_safepoint(true /* should_be_vm_thread */);
  6169   if (!free_list_only) {
  6170     TearDownRegionSetsClosure cl(&_old_set);
  6171     heap_region_iterate(&cl);
  6173     // Need to do this after the heap iteration to be able to
  6174     // recognize the young regions and ignore them during the iteration.
  6175     _young_list->empty_list();
  6177   _free_list.remove_all();
  6180 class RebuildRegionSetsClosure : public HeapRegionClosure {
  6181 private:
  6182   bool            _free_list_only;
  6183   OldRegionSet*   _old_set;
  6184   FreeRegionList* _free_list;
  6185   size_t          _total_used;
  6187 public:
  6188   RebuildRegionSetsClosure(bool free_list_only,
  6189                            OldRegionSet* old_set, FreeRegionList* free_list) :
  6190     _free_list_only(free_list_only),
  6191     _old_set(old_set), _free_list(free_list), _total_used(0) {
  6192     assert(_free_list->is_empty(), "pre-condition");
  6193     if (!free_list_only) {
  6194       assert(_old_set->is_empty(), "pre-condition");
  6198   bool doHeapRegion(HeapRegion* r) {
  6199     if (r->continuesHumongous()) {
  6200       return false;
  6203     if (r->is_empty()) {
  6204       // Add free regions to the free list
  6205       _free_list->add_as_tail(r);
  6206     } else if (!_free_list_only) {
  6207       assert(!r->is_young(), "we should not come across young regions");
  6209       if (r->isHumongous()) {
  6210         // We ignore humongous regions, we left the humongous set unchanged
  6211       } else {
  6212         // The rest should be old, add them to the old set
  6213         _old_set->add(r);
  6215       _total_used += r->used();
  6218     return false;
  6221   size_t total_used() {
  6222     return _total_used;
  6224 };
  6226 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
  6227   assert_at_safepoint(true /* should_be_vm_thread */);
  6229   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
  6230   heap_region_iterate(&cl);
  6232   if (!free_list_only) {
  6233     _summary_bytes_used = cl.total_used();
  6235   assert(_summary_bytes_used == recalculate_used(),
  6236          err_msg("inconsistent _summary_bytes_used, "
  6237                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
  6238                  _summary_bytes_used, recalculate_used()));
  6241 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
  6242   _refine_cte_cl->set_concurrent(concurrent);
  6245 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
  6246   HeapRegion* hr = heap_region_containing(p);
  6247   if (hr == NULL) {
  6248     return false;
  6249   } else {
  6250     return hr->is_in(p);
  6254 // Methods for the mutator alloc region
  6256 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
  6257                                                       bool force) {
  6258   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
  6259   assert(!force || g1_policy()->can_expand_young_list(),
  6260          "if force is true we should be able to expand the young list");
  6261   bool young_list_full = g1_policy()->is_young_list_full();
  6262   if (force || !young_list_full) {
  6263     HeapRegion* new_alloc_region = new_region(word_size,
  6264                                               false /* do_expand */);
  6265     if (new_alloc_region != NULL) {
  6266       set_region_short_lived_locked(new_alloc_region);
  6267       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
  6268       return new_alloc_region;
  6271   return NULL;
  6274 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
  6275                                                   size_t allocated_bytes) {
  6276   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
  6277   assert(alloc_region->is_young(), "all mutator alloc regions should be young");
  6279   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
  6280   _summary_bytes_used += allocated_bytes;
  6281   _hr_printer.retire(alloc_region);
  6282   // We update the eden sizes here, when the region is retired,
  6283   // instead of when it's allocated, since this is the point that its
  6284   // used space has been recored in _summary_bytes_used.
  6285   g1mm()->update_eden_size();
  6288 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
  6289                                                     bool force) {
  6290   return _g1h->new_mutator_alloc_region(word_size, force);
  6293 void G1CollectedHeap::set_par_threads() {
  6294   // Don't change the number of workers.  Use the value previously set
  6295   // in the workgroup.
  6296   assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
  6297   uint n_workers = workers()->active_workers();
  6298   assert(UseDynamicNumberOfGCThreads ||
  6299            n_workers == workers()->total_workers(),
  6300       "Otherwise should be using the total number of workers");
  6301   if (n_workers == 0) {
  6302     assert(false, "Should have been set in prior evacuation pause.");
  6303     n_workers = ParallelGCThreads;
  6304     workers()->set_active_workers(n_workers);
  6306   set_par_threads(n_workers);
  6309 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
  6310                                        size_t allocated_bytes) {
  6311   _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
  6314 // Methods for the GC alloc regions
  6316 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
  6317                                                  uint count,
  6318                                                  GCAllocPurpose ap) {
  6319   assert(FreeList_lock->owned_by_self(), "pre-condition");
  6321   if (count < g1_policy()->max_regions(ap)) {
  6322     HeapRegion* new_alloc_region = new_region(word_size,
  6323                                               true /* do_expand */);
  6324     if (new_alloc_region != NULL) {
  6325       // We really only need to do this for old regions given that we
  6326       // should never scan survivors. But it doesn't hurt to do it
  6327       // for survivors too.
  6328       new_alloc_region->set_saved_mark();
  6329       if (ap == GCAllocForSurvived) {
  6330         new_alloc_region->set_survivor();
  6331         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
  6332       } else {
  6333         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
  6335       bool during_im = g1_policy()->during_initial_mark_pause();
  6336       new_alloc_region->note_start_of_copying(during_im);
  6337       return new_alloc_region;
  6338     } else {
  6339       g1_policy()->note_alloc_region_limit_reached(ap);
  6342   return NULL;
  6345 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
  6346                                              size_t allocated_bytes,
  6347                                              GCAllocPurpose ap) {
  6348   bool during_im = g1_policy()->during_initial_mark_pause();
  6349   alloc_region->note_end_of_copying(during_im);
  6350   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
  6351   if (ap == GCAllocForSurvived) {
  6352     young_list()->add_survivor_region(alloc_region);
  6353   } else {
  6354     _old_set.add(alloc_region);
  6356   _hr_printer.retire(alloc_region);
  6359 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
  6360                                                        bool force) {
  6361   assert(!force, "not supported for GC alloc regions");
  6362   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
  6365 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
  6366                                           size_t allocated_bytes) {
  6367   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
  6368                                GCAllocForSurvived);
  6371 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
  6372                                                   bool force) {
  6373   assert(!force, "not supported for GC alloc regions");
  6374   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
  6377 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
  6378                                      size_t allocated_bytes) {
  6379   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
  6380                                GCAllocForTenured);
  6382 // Heap region set verification
  6384 class VerifyRegionListsClosure : public HeapRegionClosure {
  6385 private:
  6386   FreeRegionList*     _free_list;
  6387   OldRegionSet*       _old_set;
  6388   HumongousRegionSet* _humongous_set;
  6389   uint                _region_count;
  6391 public:
  6392   VerifyRegionListsClosure(OldRegionSet* old_set,
  6393                            HumongousRegionSet* humongous_set,
  6394                            FreeRegionList* free_list) :
  6395     _old_set(old_set), _humongous_set(humongous_set),
  6396     _free_list(free_list), _region_count(0) { }
  6398   uint region_count() { return _region_count; }
  6400   bool doHeapRegion(HeapRegion* hr) {
  6401     _region_count += 1;
  6403     if (hr->continuesHumongous()) {
  6404       return false;
  6407     if (hr->is_young()) {
  6408       // TODO
  6409     } else if (hr->startsHumongous()) {
  6410       _humongous_set->verify_next_region(hr);
  6411     } else if (hr->is_empty()) {
  6412       _free_list->verify_next_region(hr);
  6413     } else {
  6414       _old_set->verify_next_region(hr);
  6416     return false;
  6418 };
  6420 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
  6421                                              HeapWord* bottom) {
  6422   HeapWord* end = bottom + HeapRegion::GrainWords;
  6423   MemRegion mr(bottom, end);
  6424   assert(_g1_reserved.contains(mr), "invariant");
  6425   // This might return NULL if the allocation fails
  6426   return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */);
  6429 void G1CollectedHeap::verify_region_sets() {
  6430   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
  6432   // First, check the explicit lists.
  6433   _free_list.verify();
  6435     // Given that a concurrent operation might be adding regions to
  6436     // the secondary free list we have to take the lock before
  6437     // verifying it.
  6438     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
  6439     _secondary_free_list.verify();
  6441   _old_set.verify();
  6442   _humongous_set.verify();
  6444   // If a concurrent region freeing operation is in progress it will
  6445   // be difficult to correctly attributed any free regions we come
  6446   // across to the correct free list given that they might belong to
  6447   // one of several (free_list, secondary_free_list, any local lists,
  6448   // etc.). So, if that's the case we will skip the rest of the
  6449   // verification operation. Alternatively, waiting for the concurrent
  6450   // operation to complete will have a non-trivial effect on the GC's
  6451   // operation (no concurrent operation will last longer than the
  6452   // interval between two calls to verification) and it might hide
  6453   // any issues that we would like to catch during testing.
  6454   if (free_regions_coming()) {
  6455     return;
  6458   // Make sure we append the secondary_free_list on the free_list so
  6459   // that all free regions we will come across can be safely
  6460   // attributed to the free_list.
  6461   append_secondary_free_list_if_not_empty_with_lock();
  6463   // Finally, make sure that the region accounting in the lists is
  6464   // consistent with what we see in the heap.
  6465   _old_set.verify_start();
  6466   _humongous_set.verify_start();
  6467   _free_list.verify_start();
  6469   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
  6470   heap_region_iterate(&cl);
  6472   _old_set.verify_end();
  6473   _humongous_set.verify_end();
  6474   _free_list.verify_end();

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