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 /*

  * Copyright (c) 2001, 2018, 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/g1Log.hpp"

 #include "gc_implementation/g1/g1MarkSweep.hpp"

 #include "gc_implementation/g1/g1RootProcessor.hpp"

 #include "gc_implementation/g1/g1StringDedup.hpp"

 #include "gc_implementation/shared/gcHeapSummary.hpp"

 #include "gc_implementation/shared/gcTimer.hpp"

 #include "gc_implementation/shared/gcTrace.hpp"

 #include "gc_implementation/shared/gcTraceTime.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/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 Method*s may be moving,

   // so we either have to flush all bcp data or convert it into bci.

   CodeCache::gc_prologue();

   Threads::gc_prologue();

   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();

   // "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

   GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());

   GenMarkSweep::trace(" 1");

   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   // Need cleared claim bits for the roots processing

   ClassLoaderDataGraph::clear_claimed_marks();

   MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);

   {

     G1RootProcessor root_processor(g1h);

     if (ClassUnloading) {

       root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,

                                           &GenMarkSweep::follow_cld_closure,

                                           &follow_code_closure);

     } else {

       root_processor.process_all_roots_no_string_table(

                                           &GenMarkSweep::follow_root_closure,

                                           &GenMarkSweep::follow_cld_closure,

                                           &follow_code_closure);

     }

   }

   // Process reference objects found during marking

   ReferenceProcessor* rp = GenMarkSweep::ref_processor();

   assert(rp == g1h->ref_processor_stw(), "Sanity");

   rp->setup_policy(clear_all_softrefs);

   const ReferenceProcessorStats& stats =

     rp->process_discovered_references(&GenMarkSweep::is_alive,

                                       &GenMarkSweep::keep_alive,

                                       &GenMarkSweep::follow_stack_closure,

                                       NULL,

                                       gc_timer(),

                                       gc_tracer()->gc_id());

   gc_tracer()->report_gc_reference_stats(stats);

   // This is the point where the entire marking should have completed.

   assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");

   if (ClassUnloading) {

      // Unload classes and purge the SystemDictionary.

      bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);

      // Unload nmethods.

      CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);

      // Prune dead klasses from subklass/sibling/implementor lists.

      Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);

   }

   // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.

   G1CollectedHeap::heap()->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);

   if (VerifyDuringGC) {

     HandleMark hm;  // handle scope

     COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);

     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.

     if (!VerifySilently) {

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

     }

     Universe::heap()->verify(VerifySilently, VerifyOption_G1UseMarkWord);

     if (!VerifySilently) {

       gclog_or_tty->print_cr("]");

     }

   }

   gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);

 }

 void G1MarkSweep::mark_sweep_phase2() {

   // Now all live objects are marked, compute the new object addresses.

   // 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.

   GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());

   GenMarkSweep::trace("2");

   prepare_compaction();

 }

 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());

         // point all the oops to the new location

         obj->adjust_pointers();

       }

     } else {

       // This really ought to be "as_CompactibleSpace"...

       r->adjust_pointers();

     }

     return false;

   }

 };

 void G1MarkSweep::mark_sweep_phase3() {

   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   // Adjust the pointers to reflect the new locations

   GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());

   GenMarkSweep::trace("3");

   // Need cleared claim bits for the roots processing

   ClassLoaderDataGraph::clear_claimed_marks();

   CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);

   {

     G1RootProcessor root_processor(g1h);

     root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,

                                      &GenMarkSweep::adjust_cld_closure,

                                      &adjust_code_closure);

   }

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

   g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);

   // Now adjust pointers in remaining weak roots.  (All of which should

   // have been cleared if they pointed to non-surviving objects.)

   JNIHandles::weak_oops_do(&GenMarkSweep::adjust_pointer_closure);

   if (G1StringDedup::is_enabled()) {

     G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);

   }

   GenMarkSweep::adjust_marks();

   G1AdjustPointersClosure blk;

   g1h->heap_region_iterate(&blk);

 }

 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

   // 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 (code and comment not fixed for perm removal), so we tell the validate code

   // to use a higher index (saved from phase2) when verifying perm_gen.

   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());

   GenMarkSweep::trace("4");

   G1SpaceCompactClosure blk;

   g1h->heap_region_iterate(&blk);

 }

 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {

   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   g1h->heap_region_iterate(blk);

   blk->update_sets();

 }

 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {

   HeapWord* end = hr->end();

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

   assert(hr->startsHumongous(),

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

   hr->set_containing_set(NULL);

   _humongous_regions_removed.increment(1u, hr->capacity());

   _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);

   prepare_for_compaction(hr, end);

   dummy_free_list.remove_all();

 }

 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {

   // If this is the first live region that we came across which we can compact,

   // initialize the CompactPoint.

   if (!is_cp_initialized()) {

     _cp.space = hr;

     _cp.threshold = hr->initialize_threshold();

   }

   prepare_for_compaction_work(&_cp, hr, end);

 }

 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,

                                                           HeapRegion* hr,

                                                           HeapWord* end) {

   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));

 }

 void G1PrepareCompactClosure::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.

   HeapRegionSetCount empty_set;

   _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);

 }

 bool G1PrepareCompactClosure::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 {

     prepare_for_compaction(hr, hr->end());

   }

   return false;

 }