hotspot/src/share/vm/gc_implementation/g1/g1MarkSweep.cpp
author jrose
Wed, 23 Sep 2009 23:56:15 -0700
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child 5076 8b74a4b60b31
permissions -rw-r--r--
Merge
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/*
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 * Copyright 2001-2009 Sun Microsystems, Inc.  All Rights Reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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 * CA 95054 USA or visit www.sun.com if you need additional information or
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 * have any questions.
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 *
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 */
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#include "incls/_precompiled.incl"
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#include "incls/_g1MarkSweep.cpp.incl"
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class HeapRegion;
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void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
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                                      bool clear_all_softrefs) {
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  assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
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  // hook up weak ref data so it can be used during Mark-Sweep
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  assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
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  assert(rp != NULL, "should be non-NULL");
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  GenMarkSweep::_ref_processor = rp;
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  rp->setup_policy(clear_all_softrefs);
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  // When collecting the permanent generation methodOops may be moving,
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  // so we either have to flush all bcp data or convert it into bci.
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  CodeCache::gc_prologue();
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  Threads::gc_prologue();
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  // Increment the invocation count for the permanent generation, since it is
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  // implicitly collected whenever we do a full mark sweep collection.
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  SharedHeap* sh = SharedHeap::heap();
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  sh->perm_gen()->stat_record()->invocations++;
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  bool marked_for_unloading = false;
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  allocate_stacks();
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  // We should save the marks of the currently locked biased monitors.
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  // The marking doesn't preserve the marks of biased objects.
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  BiasedLocking::preserve_marks();
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  mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
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  if (VerifyDuringGC) {
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      G1CollectedHeap* g1h = G1CollectedHeap::heap();
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      g1h->checkConcurrentMark();
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  }
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  mark_sweep_phase2();
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  // Don't add any more derived pointers during phase3
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  COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
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  mark_sweep_phase3();
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  mark_sweep_phase4();
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  GenMarkSweep::restore_marks();
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  BiasedLocking::restore_marks();
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  GenMarkSweep::deallocate_stacks();
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  // We must invalidate the perm-gen rs, so that it gets rebuilt.
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  GenRemSet* rs = sh->rem_set();
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  rs->invalidate(sh->perm_gen()->used_region(), true /*whole_heap*/);
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  // "free at last gc" is calculated from these.
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  // CHF: cheating for now!!!
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  //  Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
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  //  Universe::set_heap_used_at_last_gc(Universe::heap()->used());
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  Threads::gc_epilogue();
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  CodeCache::gc_epilogue();
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  // refs processing: clean slate
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  GenMarkSweep::_ref_processor = NULL;
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}
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void G1MarkSweep::allocate_stacks() {
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  GenMarkSweep::_preserved_count_max = 0;
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  GenMarkSweep::_preserved_marks = NULL;
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  GenMarkSweep::_preserved_count = 0;
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  GenMarkSweep::_preserved_mark_stack = NULL;
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  GenMarkSweep::_preserved_oop_stack = NULL;
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  GenMarkSweep::_marking_stack =
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    new (ResourceObj::C_HEAP) GrowableArray<oop>(4000, true);
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  int size = SystemDictionary::number_of_classes() * 2;
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  GenMarkSweep::_revisit_klass_stack =
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    new (ResourceObj::C_HEAP) GrowableArray<Klass*>(size, true);
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  // (#klass/k)^2 for k ~ 10 appears a better fit, but this will have to do
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  // for now until we have a chance to work out a more optimal setting.
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  GenMarkSweep::_revisit_mdo_stack =
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    new (ResourceObj::C_HEAP) GrowableArray<DataLayout*>(size*2, true);
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}
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void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
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                                    bool clear_all_softrefs) {
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  // Recursively traverse all live objects and mark them
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  EventMark m("1 mark object");
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  TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
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  GenMarkSweep::trace(" 1");
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  SharedHeap* sh = SharedHeap::heap();
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  sh->process_strong_roots(true,  // activeate StrongRootsScope
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                           true,  // Collecting permanent generation.
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                           SharedHeap::SO_SystemClasses,
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                           &GenMarkSweep::follow_root_closure,
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                           &GenMarkSweep::follow_code_root_closure,
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                           &GenMarkSweep::follow_root_closure);
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  // Process reference objects found during marking
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  ReferenceProcessor* rp = GenMarkSweep::ref_processor();
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  rp->setup_policy(clear_all_softrefs);
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  rp->process_discovered_references(&GenMarkSweep::is_alive,
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                                    &GenMarkSweep::keep_alive,
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                                    &GenMarkSweep::follow_stack_closure,
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                                    NULL);
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  // Follow system dictionary roots and unload classes
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  bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
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  assert(GenMarkSweep::_marking_stack->is_empty(),
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         "stack should be empty by now");
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  // Follow code cache roots (has to be done after system dictionary,
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  // assumes all live klasses are marked)
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  CodeCache::do_unloading(&GenMarkSweep::is_alive,
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                                   &GenMarkSweep::keep_alive,
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                                   purged_class);
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  GenMarkSweep::follow_stack();
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  // Update subklass/sibling/implementor links of live klasses
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  GenMarkSweep::follow_weak_klass_links();
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  assert(GenMarkSweep::_marking_stack->is_empty(),
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         "stack should be empty by now");
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  // Visit memoized MDO's and clear any unmarked weak refs
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  GenMarkSweep::follow_mdo_weak_refs();
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  assert(GenMarkSweep::_marking_stack->is_empty(), "just drained");
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  // Visit symbol and interned string tables and delete unmarked oops
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  SymbolTable::unlink(&GenMarkSweep::is_alive);
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  StringTable::unlink(&GenMarkSweep::is_alive);
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  assert(GenMarkSweep::_marking_stack->is_empty(),
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         "stack should be empty by now");
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}
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class G1PrepareCompactClosure: public HeapRegionClosure {
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  ModRefBarrierSet* _mrbs;
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  CompactPoint _cp;
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  void free_humongous_region(HeapRegion* hr) {
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    HeapWord* bot = hr->bottom();
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    HeapWord* end = hr->end();
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    assert(hr->startsHumongous(),
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           "Only the start of a humongous region should be freed.");
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    G1CollectedHeap::heap()->free_region(hr);
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    hr->prepare_for_compaction(&_cp);
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    // Also clear the part of the card table that will be unused after
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    // compaction.
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    _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
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  }
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  G1PrepareCompactClosure(CompactibleSpace* cs) :
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    _cp(NULL, cs, cs->initialize_threshold()),
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    _mrbs(G1CollectedHeap::heap()->mr_bs())
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  {}
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  bool doHeapRegion(HeapRegion* hr) {
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    if (hr->isHumongous()) {
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      if (hr->startsHumongous()) {
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        oop obj = oop(hr->bottom());
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        if (obj->is_gc_marked()) {
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          obj->forward_to(obj);
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        } else  {
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          free_humongous_region(hr);
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        }
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      } else {
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        assert(hr->continuesHumongous(), "Invalid humongous.");
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      }
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    } else {
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      hr->prepare_for_compaction(&_cp);
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      // Also clear the part of the card table that will be unused after
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      // compaction.
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      _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
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    }
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    return false;
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  }
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};
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// Finds the first HeapRegion.
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class FindFirstRegionClosure: public HeapRegionClosure {
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  HeapRegion* _a_region;
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  FindFirstRegionClosure() : _a_region(NULL) {}
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  bool doHeapRegion(HeapRegion* r) {
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    _a_region = r;
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    return true;
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  }
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  HeapRegion* result() { return _a_region; }
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};
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void G1MarkSweep::mark_sweep_phase2() {
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  // Now all live objects are marked, compute the new object addresses.
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  // It is imperative that we traverse perm_gen LAST. If dead space is
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  // allowed a range of dead object may get overwritten by a dead int
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  // array. If perm_gen is not traversed last a klassOop may get
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  // overwritten. This is fine since it is dead, but if the class has dead
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  // instances we have to skip them, and in order to find their size we
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  // need the klassOop!
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  //
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  // It is not required that we traverse spaces in the same order in
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  // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
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  // tracking expects us to do so. See comment under phase4.
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  G1CollectedHeap* g1h = G1CollectedHeap::heap();
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  Generation* pg = g1h->perm_gen();
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  EventMark m("2 compute new addresses");
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  TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
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  GenMarkSweep::trace("2");
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  FindFirstRegionClosure cl;
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  g1h->heap_region_iterate(&cl);
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  HeapRegion *r = cl.result();
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  CompactibleSpace* sp = r;
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  if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
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    sp = r->next_compaction_space();
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  }
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  G1PrepareCompactClosure blk(sp);
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  g1h->heap_region_iterate(&blk);
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  CompactPoint perm_cp(pg, NULL, NULL);
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  pg->prepare_for_compaction(&perm_cp);
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}
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class G1AdjustPointersClosure: public HeapRegionClosure {
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 public:
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  bool doHeapRegion(HeapRegion* r) {
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    if (r->isHumongous()) {
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      if (r->startsHumongous()) {
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        // We must adjust the pointers on the single H object.
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        oop obj = oop(r->bottom());
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        debug_only(GenMarkSweep::track_interior_pointers(obj));
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        // point all the oops to the new location
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        obj->adjust_pointers();
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        debug_only(GenMarkSweep::check_interior_pointers());
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      }
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    } else {
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      // This really ought to be "as_CompactibleSpace"...
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      r->adjust_pointers();
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    }
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    return false;
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  }
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};
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void G1MarkSweep::mark_sweep_phase3() {
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  G1CollectedHeap* g1h = G1CollectedHeap::heap();
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  Generation* pg = g1h->perm_gen();
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  // Adjust the pointers to reflect the new locations
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  EventMark m("3 adjust pointers");
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  TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
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  GenMarkSweep::trace("3");
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  SharedHeap* sh = SharedHeap::heap();
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  sh->process_strong_roots(true,  // activate StrongRootsScope
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                           true,  // Collecting permanent generation.
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                           SharedHeap::SO_AllClasses,
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                           &GenMarkSweep::adjust_root_pointer_closure,
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                           NULL,  // do not touch code cache here
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                           &GenMarkSweep::adjust_pointer_closure);
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  g1h->ref_processor()->weak_oops_do(&GenMarkSweep::adjust_root_pointer_closure);
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  // Now adjust pointers in remaining weak roots.  (All of which should
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  // have been cleared if they pointed to non-surviving objects.)
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  g1h->g1_process_weak_roots(&GenMarkSweep::adjust_root_pointer_closure,
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                             &GenMarkSweep::adjust_pointer_closure);
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  GenMarkSweep::adjust_marks();
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  G1AdjustPointersClosure blk;
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  g1h->heap_region_iterate(&blk);
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  pg->adjust_pointers();
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}
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class G1SpaceCompactClosure: public HeapRegionClosure {
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public:
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  G1SpaceCompactClosure() {}
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  bool doHeapRegion(HeapRegion* hr) {
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    if (hr->isHumongous()) {
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      if (hr->startsHumongous()) {
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        oop obj = oop(hr->bottom());
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        if (obj->is_gc_marked()) {
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          obj->init_mark();
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        } else {
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          assert(hr->is_empty(), "Should have been cleared in phase 2.");
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        }
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        hr->reset_during_compaction();
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      }
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    } else {
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      hr->compact();
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    }
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    return false;
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  }
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};
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void G1MarkSweep::mark_sweep_phase4() {
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  // All pointers are now adjusted, move objects accordingly
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  // It is imperative that we traverse perm_gen first in phase4. All
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  // classes must be allocated earlier than their instances, and traversing
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  // perm_gen first makes sure that all klassOops have moved to their new
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  // location before any instance does a dispatch through it's klass!
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  // The ValidateMarkSweep live oops tracking expects us to traverse spaces
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  // in the same order in phase2, phase3 and phase4. We don't quite do that
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  // here (perm_gen first rather than last), so we tell the validate code
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  // to use a higher index (saved from phase2) when verifying perm_gen.
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  G1CollectedHeap* g1h = G1CollectedHeap::heap();
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  Generation* pg = g1h->perm_gen();
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  EventMark m("4 compact heap");
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  TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
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  GenMarkSweep::trace("4");
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  pg->compact();
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  G1SpaceCompactClosure blk;
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  g1h->heap_region_iterate(&blk);
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}
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// Local Variables: ***
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// c-indentation-style: gnu ***
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// End: ***