hotspot/src/share/vm/gc_implementation/g1/g1MarkSweep.cpp - platform/libcore - Git at Google

 /*
  * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */

 #include "precompiled.hpp"
 #include "classfile/javaClasses.hpp"
 #include "classfile/symbolTable.hpp"
 #include "classfile/systemDictionary.hpp"
 #include "classfile/vmSymbols.hpp"
 #include "code/codeCache.hpp"
 #include "code/icBuffer.hpp"
 #include "gc_implementation/g1/g1MarkSweep.hpp"
 #include "memory/gcLocker.hpp"
 #include "memory/genCollectedHeap.hpp"
 #include "memory/modRefBarrierSet.hpp"
 #include "memory/referencePolicy.hpp"
 #include "memory/space.hpp"
 #include "oops/instanceRefKlass.hpp"
 #include "oops/oop.inline.hpp"
 #include "prims/jvmtiExport.hpp"
 #include "runtime/aprofiler.hpp"
 #include "runtime/biasedLocking.hpp"
 #include "runtime/fprofiler.hpp"
 #include "runtime/synchronizer.hpp"
 #include "runtime/thread.hpp"
 #include "runtime/vmThread.hpp"
 #include "utilities/copy.hpp"
 #include "utilities/events.hpp"

 class HeapRegion;

 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
                                       bool clear_all_softrefs) {
   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");

   SharedHeap* sh = SharedHeap::heap();
 #ifdef ASSERT
   if (sh->collector_policy()->should_clear_all_soft_refs()) {
     assert(clear_all_softrefs, "Policy should have been checked earler");
   }
 #endif
   // hook up weak ref data so it can be used during Mark-Sweep
   assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
   assert(rp != NULL, "should be non-NULL");
   GenMarkSweep::_ref_processor = rp;
   rp->setup_policy(clear_all_softrefs);

   // When collecting the permanent generation methodOops may be moving,
   // so we either have to flush all bcp data or convert it into bci.
   CodeCache::gc_prologue();
   Threads::gc_prologue();

   // Increment the invocation count for the permanent generation, since it is
   // implicitly collected whenever we do a full mark sweep collection.
   sh->perm_gen()->stat_record()->invocations++;

   bool marked_for_unloading = false;

   allocate_stacks();

   // We should save the marks of the currently locked biased monitors.
   // The marking doesn't preserve the marks of biased objects.
   BiasedLocking::preserve_marks();

   mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);

   if (VerifyDuringGC) {
       G1CollectedHeap* g1h = G1CollectedHeap::heap();
       g1h->checkConcurrentMark();
   }

   mark_sweep_phase2();

   // Don't add any more derived pointers during phase3
   COMPILER2_PRESENT(DerivedPointerTable::set_active(false));

   mark_sweep_phase3();

   mark_sweep_phase4();

   GenMarkSweep::restore_marks();
   BiasedLocking::restore_marks();
   GenMarkSweep::deallocate_stacks();

   // We must invalidate the perm-gen rs, so that it gets rebuilt.
   GenRemSet* rs = sh->rem_set();
   rs->invalidate(sh->perm_gen()->used_region(), true /*whole_heap*/);

   // "free at last gc" is calculated from these.
   // CHF: cheating for now!!!
   //  Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
   //  Universe::set_heap_used_at_last_gc(Universe::heap()->used());

   Threads::gc_epilogue();
   CodeCache::gc_epilogue();

   // refs processing: clean slate
   GenMarkSweep::_ref_processor = NULL;
 }


 void G1MarkSweep::allocate_stacks() {
   GenMarkSweep::_preserved_count_max = 0;
   GenMarkSweep::_preserved_marks = NULL;
   GenMarkSweep::_preserved_count = 0;
 }

 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
                                     bool clear_all_softrefs) {
   // Recursively traverse all live objects and mark them
   EventMark m("1 mark object");
   TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
   GenMarkSweep::trace(" 1");

   SharedHeap* sh = SharedHeap::heap();

   sh->process_strong_roots(true,  // activeate StrongRootsScope
                            true,  // Collecting permanent generation.
                            SharedHeap::SO_SystemClasses,
                            &GenMarkSweep::follow_root_closure,
                            &GenMarkSweep::follow_code_root_closure,
                            &GenMarkSweep::follow_root_closure);

   // Process reference objects found during marking
   ReferenceProcessor* rp = GenMarkSweep::ref_processor();
   rp->setup_policy(clear_all_softrefs);
   rp->process_discovered_references(&GenMarkSweep::is_alive,
                                     &GenMarkSweep::keep_alive,
                                     &GenMarkSweep::follow_stack_closure,
                                     NULL);

   // Follow system dictionary roots and unload classes
   bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
   assert(GenMarkSweep::_marking_stack.is_empty(),
          "stack should be empty by now");

   // Follow code cache roots (has to be done after system dictionary,
   // assumes all live klasses are marked)
   CodeCache::do_unloading(&GenMarkSweep::is_alive,
                                    &GenMarkSweep::keep_alive,
                                    purged_class);
   GenMarkSweep::follow_stack();

   // Update subklass/sibling/implementor links of live klasses
   GenMarkSweep::follow_weak_klass_links();
   assert(GenMarkSweep::_marking_stack.is_empty(),
          "stack should be empty by now");

   // Visit memoized MDO's and clear any unmarked weak refs
   GenMarkSweep::follow_mdo_weak_refs();
   assert(GenMarkSweep::_marking_stack.is_empty(), "just drained");


   // Visit symbol and interned string tables and delete unmarked oops
   SymbolTable::unlink(&GenMarkSweep::is_alive);
   StringTable::unlink(&GenMarkSweep::is_alive);

   assert(GenMarkSweep::_marking_stack.is_empty(),
          "stack should be empty by now");
 }

 class G1PrepareCompactClosure: public HeapRegionClosure {
   G1CollectedHeap* _g1h;
   ModRefBarrierSet* _mrbs;
   CompactPoint _cp;
   size_t _pre_used;
   FreeRegionList _free_list;
   HumongousRegionSet _humongous_proxy_set;

   void free_humongous_region(HeapRegion* hr) {
     HeapWord* end = hr->end();
     assert(hr->startsHumongous(),
            "Only the start of a humongous region should be freed.");
     _g1h->free_humongous_region(hr, &_pre_used, &_free_list,
                                 &_humongous_proxy_set, false /* par */);
     // Do we also need to do this for the continues humongous regions
     // we just collapsed?
     hr->prepare_for_compaction(&_cp);
     // Also clear the part of the card table that will be unused after
     // compaction.
     _mrbs->clear(MemRegion(hr->compaction_top(), end));
   }

 public:
   G1PrepareCompactClosure(CompactibleSpace* cs)
   : _g1h(G1CollectedHeap::heap()),
     _mrbs(G1CollectedHeap::heap()->mr_bs()),
     _cp(NULL, cs, cs->initialize_threshold()),
     _pre_used(0),
     _free_list("Local Free List for G1MarkSweep"),
     _humongous_proxy_set("G1MarkSweep Humongous Proxy Set") { }

   void update_sets() {
     // We'll recalculate total used bytes and recreate the free list
     // at the end of the GC, so no point in updating those values here.
     _g1h->update_sets_after_freeing_regions(0, /* pre_used */
                                             NULL, /* free_list */
                                             &_humongous_proxy_set,
                                             false /* par */);
     _free_list.remove_all();
   }

   bool doHeapRegion(HeapRegion* hr) {
     if (hr->isHumongous()) {
       if (hr->startsHumongous()) {
         oop obj = oop(hr->bottom());
         if (obj->is_gc_marked()) {
           obj->forward_to(obj);
         } else  {
           free_humongous_region(hr);
         }
       } else {
         assert(hr->continuesHumongous(), "Invalid humongous.");
       }
     } else {
       hr->prepare_for_compaction(&_cp);
       // Also clear the part of the card table that will be unused after
       // compaction.
       _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
     }
     return false;
   }
 };

 // Finds the first HeapRegion.
 class FindFirstRegionClosure: public HeapRegionClosure {
   HeapRegion* _a_region;
 public:
   FindFirstRegionClosure() : _a_region(NULL) {}
   bool doHeapRegion(HeapRegion* r) {
     _a_region = r;
     return true;
   }
   HeapRegion* result() { return _a_region; }
 };

 void G1MarkSweep::mark_sweep_phase2() {
   // Now all live objects are marked, compute the new object addresses.

   // It is imperative that we traverse perm_gen LAST. If dead space is
   // allowed a range of dead object may get overwritten by a dead int
   // array. If perm_gen is not traversed last a klassOop may get
   // overwritten. This is fine since it is dead, but if the class has dead
   // instances we have to skip them, and in order to find their size we
   // need the klassOop!
   //
   // It is not required that we traverse spaces in the same order in
   // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
   // tracking expects us to do so. See comment under phase4.

   G1CollectedHeap* g1h = G1CollectedHeap::heap();
   Generation* pg = g1h->perm_gen();

   EventMark m("2 compute new addresses");
   TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
   GenMarkSweep::trace("2");

   FindFirstRegionClosure cl;
   g1h->heap_region_iterate(&cl);
   HeapRegion *r = cl.result();
   CompactibleSpace* sp = r;
   if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
     sp = r->next_compaction_space();
   }

   G1PrepareCompactClosure blk(sp);
   g1h->heap_region_iterate(&blk);
   blk.update_sets();

   CompactPoint perm_cp(pg, NULL, NULL);
   pg->prepare_for_compaction(&perm_cp);
 }

 class G1AdjustPointersClosure: public HeapRegionClosure {
  public:
   bool doHeapRegion(HeapRegion* r) {
     if (r->isHumongous()) {
       if (r->startsHumongous()) {
         // We must adjust the pointers on the single H object.
         oop obj = oop(r->bottom());
         debug_only(GenMarkSweep::track_interior_pointers(obj));
         // point all the oops to the new location
         obj->adjust_pointers();
         debug_only(GenMarkSweep::check_interior_pointers());
       }
     } else {
       // This really ought to be "as_CompactibleSpace"...
       r->adjust_pointers();
     }
     return false;
   }
 };

 void G1MarkSweep::mark_sweep_phase3() {
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
   Generation* pg = g1h->perm_gen();

   // Adjust the pointers to reflect the new locations
   EventMark m("3 adjust pointers");
   TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
   GenMarkSweep::trace("3");

   SharedHeap* sh = SharedHeap::heap();

   sh->process_strong_roots(true,  // activate StrongRootsScope
                            true,  // Collecting permanent generation.
                            SharedHeap::SO_AllClasses,
                            &GenMarkSweep::adjust_root_pointer_closure,
                            NULL,  // do not touch code cache here
                            &GenMarkSweep::adjust_pointer_closure);

   g1h->ref_processor()->weak_oops_do(&GenMarkSweep::adjust_root_pointer_closure);

   // Now adjust pointers in remaining weak roots.  (All of which should
   // have been cleared if they pointed to non-surviving objects.)
   g1h->g1_process_weak_roots(&GenMarkSweep::adjust_root_pointer_closure,
                              &GenMarkSweep::adjust_pointer_closure);

   GenMarkSweep::adjust_marks();

   G1AdjustPointersClosure blk;
   g1h->heap_region_iterate(&blk);
   pg->adjust_pointers();
 }

 class G1SpaceCompactClosure: public HeapRegionClosure {
 public:
   G1SpaceCompactClosure() {}

   bool doHeapRegion(HeapRegion* hr) {
     if (hr->isHumongous()) {
       if (hr->startsHumongous()) {
         oop obj = oop(hr->bottom());
         if (obj->is_gc_marked()) {
           obj->init_mark();
         } else {
           assert(hr->is_empty(), "Should have been cleared in phase 2.");
         }
         hr->reset_during_compaction();
       }
     } else {
       hr->compact();
     }
     return false;
   }
 };

 void G1MarkSweep::mark_sweep_phase4() {
   // All pointers are now adjusted, move objects accordingly

   // It is imperative that we traverse perm_gen first in phase4. All
   // classes must be allocated earlier than their instances, and traversing
   // perm_gen first makes sure that all klassOops have moved to their new
   // location before any instance does a dispatch through it's klass!

   // The ValidateMarkSweep live oops tracking expects us to traverse spaces
   // in the same order in phase2, phase3 and phase4. We don't quite do that
   // here (perm_gen first rather than last), so we tell the validate code
   // to use a higher index (saved from phase2) when verifying perm_gen.
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
   Generation* pg = g1h->perm_gen();

   EventMark m("4 compact heap");
   TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
   GenMarkSweep::trace("4");

   pg->compact();

   G1SpaceCompactClosure blk;
   g1h->heap_region_iterate(&blk);

 }

 // Local Variables: ***
 // c-indentation-style: gnu ***
 // End: ***
	/*
	* Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*
	*/

	#include "precompiled.hpp"
	#include "classfile/javaClasses.hpp"
	#include "classfile/symbolTable.hpp"
	#include "classfile/systemDictionary.hpp"
	#include "classfile/vmSymbols.hpp"
	#include "code/codeCache.hpp"
	#include "code/icBuffer.hpp"
	#include "gc_implementation/g1/g1MarkSweep.hpp"
	#include "memory/gcLocker.hpp"
	#include "memory/genCollectedHeap.hpp"
	#include "memory/modRefBarrierSet.hpp"
	#include "memory/referencePolicy.hpp"
	#include "memory/space.hpp"
	#include "oops/instanceRefKlass.hpp"
	#include "oops/oop.inline.hpp"
	#include "prims/jvmtiExport.hpp"
	#include "runtime/aprofiler.hpp"
	#include "runtime/biasedLocking.hpp"
	#include "runtime/fprofiler.hpp"
	#include "runtime/synchronizer.hpp"
	#include "runtime/thread.hpp"
	#include "runtime/vmThread.hpp"
	#include "utilities/copy.hpp"
	#include "utilities/events.hpp"

	class HeapRegion;

	void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
	bool clear_all_softrefs) {
	assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");

	SharedHeap* sh = SharedHeap::heap();
	#ifdef ASSERT
	if (sh->collector_policy()->should_clear_all_soft_refs()) {
	assert(clear_all_softrefs, "Policy should have been checked earler");
	}
	#endif
	// hook up weak ref data so it can be used during Mark-Sweep
	assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
	assert(rp != NULL, "should be non-NULL");
	GenMarkSweep::_ref_processor = rp;
	rp->setup_policy(clear_all_softrefs);

	// When collecting the permanent generation methodOops may be moving,
	// so we either have to flush all bcp data or convert it into bci.
	CodeCache::gc_prologue();
	Threads::gc_prologue();

	// Increment the invocation count for the permanent generation, since it is
	// implicitly collected whenever we do a full mark sweep collection.
	sh->perm_gen()->stat_record()->invocations++;

	bool marked_for_unloading = false;

	allocate_stacks();

	// We should save the marks of the currently locked biased monitors.
	// The marking doesn't preserve the marks of biased objects.
	BiasedLocking::preserve_marks();

	mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);

	if (VerifyDuringGC) {
	G1CollectedHeap* g1h = G1CollectedHeap::heap();
	g1h->checkConcurrentMark();
	}

	mark_sweep_phase2();

	// Don't add any more derived pointers during phase3
	COMPILER2_PRESENT(DerivedPointerTable::set_active(false));

	mark_sweep_phase3();

	mark_sweep_phase4();

	GenMarkSweep::restore_marks();
	BiasedLocking::restore_marks();
	GenMarkSweep::deallocate_stacks();

	// We must invalidate the perm-gen rs, so that it gets rebuilt.
	GenRemSet* rs = sh->rem_set();
	rs->invalidate(sh->perm_gen()->used_region(), true /whole_heap/);

	// "free at last gc" is calculated from these.
	// CHF: cheating for now!!!
	// Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
	// Universe::set_heap_used_at_last_gc(Universe::heap()->used());

	Threads::gc_epilogue();
	CodeCache::gc_epilogue();

	// refs processing: clean slate
	GenMarkSweep::_ref_processor = NULL;
	}


	void G1MarkSweep::allocate_stacks() {
	GenMarkSweep::_preserved_count_max = 0;
	GenMarkSweep::_preserved_marks = NULL;
	GenMarkSweep::_preserved_count = 0;
	}

	void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
	bool clear_all_softrefs) {
	// Recursively traverse all live objects and mark them
	EventMark m("1 mark object");
	TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
	GenMarkSweep::trace(" 1");

	SharedHeap* sh = SharedHeap::heap();

	sh->process_strong_roots(true, // activeate StrongRootsScope
	true, // Collecting permanent generation.
	SharedHeap::SO_SystemClasses,
	&GenMarkSweep::follow_root_closure,
	&GenMarkSweep::follow_code_root_closure,
	&GenMarkSweep::follow_root_closure);

	// Process reference objects found during marking
	ReferenceProcessor* rp = GenMarkSweep::ref_processor();
	rp->setup_policy(clear_all_softrefs);
	rp->process_discovered_references(&GenMarkSweep::is_alive,
	&GenMarkSweep::keep_alive,
	&GenMarkSweep::follow_stack_closure,
	NULL);

	// Follow system dictionary roots and unload classes
	bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
	assert(GenMarkSweep::_marking_stack.is_empty(),
	"stack should be empty by now");

	// Follow code cache roots (has to be done after system dictionary,
	// assumes all live klasses are marked)
	CodeCache::do_unloading(&GenMarkSweep::is_alive,
	&GenMarkSweep::keep_alive,
	purged_class);
	GenMarkSweep::follow_stack();

	// Update subklass/sibling/implementor links of live klasses
	GenMarkSweep::follow_weak_klass_links();
	assert(GenMarkSweep::_marking_stack.is_empty(),
	"stack should be empty by now");

	// Visit memoized MDO's and clear any unmarked weak refs
	GenMarkSweep::follow_mdo_weak_refs();
	assert(GenMarkSweep::_marking_stack.is_empty(), "just drained");


	// Visit symbol and interned string tables and delete unmarked oops
	SymbolTable::unlink(&GenMarkSweep::is_alive);
	StringTable::unlink(&GenMarkSweep::is_alive);

	assert(GenMarkSweep::_marking_stack.is_empty(),
	"stack should be empty by now");
	}

	class G1PrepareCompactClosure: public HeapRegionClosure {
	G1CollectedHeap* _g1h;
	ModRefBarrierSet* _mrbs;
	CompactPoint _cp;
	size_t _pre_used;
	FreeRegionList _free_list;
	HumongousRegionSet _humongous_proxy_set;

	void free_humongous_region(HeapRegion* hr) {
	HeapWord* end = hr->end();
	assert(hr->startsHumongous(),
	"Only the start of a humongous region should be freed.");
	_g1h->free_humongous_region(hr, &_pre_used, &_free_list,
	&_humongous_proxy_set, false /* par */);
	// Do we also need to do this for the continues humongous regions
	// we just collapsed?
	hr->prepare_for_compaction(&_cp);
	// Also clear the part of the card table that will be unused after
	// compaction.
	_mrbs->clear(MemRegion(hr->compaction_top(), end));
	}

	public:
	G1PrepareCompactClosure(CompactibleSpace* cs)
	: _g1h(G1CollectedHeap::heap()),
	_mrbs(G1CollectedHeap::heap()->mr_bs()),
	_cp(NULL, cs, cs->initialize_threshold()),
	_pre_used(0),
	_free_list("Local Free List for G1MarkSweep"),
	_humongous_proxy_set("G1MarkSweep Humongous Proxy Set") { }

	void update_sets() {
	// We'll recalculate total used bytes and recreate the free list
	// at the end of the GC, so no point in updating those values here.
	_g1h->update_sets_after_freeing_regions(0, /* pre_used */
	NULL, /* free_list */
	&_humongous_proxy_set,
	false /* par */);
	_free_list.remove_all();
	}

	bool doHeapRegion(HeapRegion* hr) {
	if (hr->isHumongous()) {
	if (hr->startsHumongous()) {
	oop obj = oop(hr->bottom());
	if (obj->is_gc_marked()) {
	obj->forward_to(obj);
	} else {
	free_humongous_region(hr);
	}
	} else {
	assert(hr->continuesHumongous(), "Invalid humongous.");
	}
	} else {
	hr->prepare_for_compaction(&_cp);
	// Also clear the part of the card table that will be unused after
	// compaction.
	_mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
	}
	return false;
	}
	};

	// Finds the first HeapRegion.
	class FindFirstRegionClosure: public HeapRegionClosure {
	HeapRegion* _a_region;
	public:
	FindFirstRegionClosure() : _a_region(NULL) {}
	bool doHeapRegion(HeapRegion* r) {
	_a_region = r;
	return true;
	}
	HeapRegion* result() { return _a_region; }
	};

	void G1MarkSweep::mark_sweep_phase2() {
	// Now all live objects are marked, compute the new object addresses.

	// It is imperative that we traverse perm_gen LAST. If dead space is
	// allowed a range of dead object may get overwritten by a dead int
	// array. If perm_gen is not traversed last a klassOop may get
	// overwritten. This is fine since it is dead, but if the class has dead
	// instances we have to skip them, and in order to find their size we
	// need the klassOop!
	//
	// It is not required that we traverse spaces in the same order in
	// phase2, phase3 and phase4, but the ValidateMarkSweep live oops
	// tracking expects us to do so. See comment under phase4.

	G1CollectedHeap* g1h = G1CollectedHeap::heap();
	Generation* pg = g1h->perm_gen();

	EventMark m("2 compute new addresses");
	TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
	GenMarkSweep::trace("2");

	FindFirstRegionClosure cl;
	g1h->heap_region_iterate(&cl);
	HeapRegion *r = cl.result();
	CompactibleSpace* sp = r;
	if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
	sp = r->next_compaction_space();
	}

	G1PrepareCompactClosure blk(sp);
	g1h->heap_region_iterate(&blk);
	blk.update_sets();

	CompactPoint perm_cp(pg, NULL, NULL);
	pg->prepare_for_compaction(&perm_cp);
	}

	class G1AdjustPointersClosure: public HeapRegionClosure {
	public:
	bool doHeapRegion(HeapRegion* r) {
	if (r->isHumongous()) {
	if (r->startsHumongous()) {
	// We must adjust the pointers on the single H object.
	oop obj = oop(r->bottom());
	debug_only(GenMarkSweep::track_interior_pointers(obj));
	// point all the oops to the new location
	obj->adjust_pointers();
	debug_only(GenMarkSweep::check_interior_pointers());
	}
	} else {
	// This really ought to be "as_CompactibleSpace"...
	r->adjust_pointers();
	}
	return false;
	}
	};

	void G1MarkSweep::mark_sweep_phase3() {
	G1CollectedHeap* g1h = G1CollectedHeap::heap();
	Generation* pg = g1h->perm_gen();

	// Adjust the pointers to reflect the new locations
	EventMark m("3 adjust pointers");
	TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
	GenMarkSweep::trace("3");

	SharedHeap* sh = SharedHeap::heap();

	sh->process_strong_roots(true, // activate StrongRootsScope
	true, // Collecting permanent generation.
	SharedHeap::SO_AllClasses,
	&GenMarkSweep::adjust_root_pointer_closure,
	NULL, // do not touch code cache here
	&GenMarkSweep::adjust_pointer_closure);

	g1h->ref_processor()->weak_oops_do(&GenMarkSweep::adjust_root_pointer_closure);

	// Now adjust pointers in remaining weak roots. (All of which should
	// have been cleared if they pointed to non-surviving objects.)
	g1h->g1_process_weak_roots(&GenMarkSweep::adjust_root_pointer_closure,
	&GenMarkSweep::adjust_pointer_closure);

	GenMarkSweep::adjust_marks();

	G1AdjustPointersClosure blk;
	g1h->heap_region_iterate(&blk);
	pg->adjust_pointers();
	}

	class G1SpaceCompactClosure: public HeapRegionClosure {
	public:
	G1SpaceCompactClosure() {}

	bool doHeapRegion(HeapRegion* hr) {
	if (hr->isHumongous()) {
	if (hr->startsHumongous()) {
	oop obj = oop(hr->bottom());
	if (obj->is_gc_marked()) {
	obj->init_mark();
	} else {
	assert(hr->is_empty(), "Should have been cleared in phase 2.");
	}
	hr->reset_during_compaction();
	}
	} else {
	hr->compact();
	}
	return false;
	}
	};

	void G1MarkSweep::mark_sweep_phase4() {
	// All pointers are now adjusted, move objects accordingly

	// It is imperative that we traverse perm_gen first in phase4. All
	// classes must be allocated earlier than their instances, and traversing
	// perm_gen first makes sure that all klassOops have moved to their new
	// location before any instance does a dispatch through it's klass!

	// The ValidateMarkSweep live oops tracking expects us to traverse spaces
	// in the same order in phase2, phase3 and phase4. We don't quite do that
	// here (perm_gen first rather than last), so we tell the validate code
	// to use a higher index (saved from phase2) when verifying perm_gen.
	G1CollectedHeap* g1h = G1CollectedHeap::heap();
	Generation* pg = g1h->perm_gen();

	EventMark m("4 compact heap");
	TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
	GenMarkSweep::trace("4");

	pg->compact();

	G1SpaceCompactClosure blk;
	g1h->heap_region_iterate(&blk);

	}

	// Local Variables: ***
	// c-indentation-style: gnu ***
	// End: ***