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 /*

  * 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

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  */

 #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");

   assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");

   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);

   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();

   JvmtiExport::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();

   assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Sanity");

   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 interned string tables and delete unmarked oops

   StringTable::unlink(&GenMarkSweep::is_alive);

   // Clean up unreferenced symbols in symbol table.

   SymbolTable::unlink();

   assert(GenMarkSweep::_marking_stack.is_empty(),

          "stack should be empty by now");

   if (VerifyDuringGC) {

     HandleMark hm;  // handle scope

     COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);

     gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");

     Universe::heap()->prepare_for_verify();

     // Note: we can verify only the heap here. When an object is

     // marked, the previous value of the mark word (including

     // identity hash values, ages, etc) is preserved, and the mark

     // word is set to markOop::marked_value - effectively removing

     // any hash values from the mark word. These hash values are

     // used when verifying the dictionaries and so removing them

     // from the mark word can make verification of the dictionaries

     // fail. At the end of the GC, the orginal mark word values

     // (including hash values) are restored to the appropriate

     // objects.

     Universe::heap()->verify(/* allow dirty */ true,

                              /* silent      */ false,

                              /* option      */ VerifyOption_G1UseMarkWord);

     G1CollectedHeap* g1h = G1CollectedHeap::heap();

     gclog_or_tty->print_cr("]");

   }

 }

 class G1PrepareCompactClosure: public HeapRegionClosure {

   G1CollectedHeap* _g1h;

   ModRefBarrierSet* _mrbs;

   CompactPoint _cp;

   HumongousRegionSet _humongous_proxy_set;

   void free_humongous_region(HeapRegion* hr) {

     HeapWord* end = hr->end();

     size_t dummy_pre_used;

     FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");

     assert(hr->startsHumongous(),

            "Only the start of a humongous region should be freed.");

     _g1h->free_humongous_region(hr, &dummy_pre_used, &dummy_free_list,

                                 &_humongous_proxy_set, false /* par */);

     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));

     dummy_free_list.remove_all();

   }

 public:

   G1PrepareCompactClosure(CompactibleSpace* cs)

   : _g1h(G1CollectedHeap::heap()),

     _mrbs(G1CollectedHeap::heap()->mr_bs()),

     _cp(NULL, cs, cs->initialize_threshold()),

     _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 */);

   }

   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);

   assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");

   g1h->ref_processor_stw()->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);

 }

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