/*

 * Copyright (c) 2001, 2015, 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/g1Log.hpp"

#include "gc_implementation/g1/g1MarkSweep.hpp"

#include "gc_implementation/g1/g1RootProcessor.hpp"

#include "gc_implementation/g1/g1StringDedup.hpp"

#include "gc_implementation/shared/markSweep.inline.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/atomic.inline.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");

#ifdef ASSERT

  if (G1CollectedHeap::heap()->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();

  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();

  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());

  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);

    root_processor.process_strong_roots(&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");

  // 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.

  g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);

  if (VerifyDuringGC) {

    HandleMark hm;  // handle scope

    COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);

    g1h->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 original mark word values

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

    // objects.

    if (!VerifySilently) {

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

    }

    g1h->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());

  prepare_compaction();

}

class G1AdjustPointersClosure: public HeapRegionClosure {

 public:

  bool doHeapRegion(HeapRegion* r) {

    if (r->is_humongous()) {

      if (r->is_starts_humongous()) {

        // We must adjust the pointers on the single H object.

        oop obj = oop(r->bottom());

        // point all the oops to the new location

        MarkSweep::adjust_pointers(obj);

      }

    } else {

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

      r->adjust_pointers();

    }

    return false;

  }

};

class G1AlwaysTrueClosure: public BoolObjectClosure {

public:

  bool do_object_b(oop p) { return true; }

};

static G1AlwaysTrueClosure always_true;

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());

  // 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(&always_true, &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->is_humongous()) {

      if (hr->is_starts_humongous()) {

        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());

  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->is_starts_humongous(),

         "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->is_humongous()) {

    if (hr->is_starts_humongous()) {

      oop obj = oop(hr->bottom());

      if (obj->is_gc_marked()) {

        obj->forward_to(obj);

      } else  {

        free_humongous_region(hr);

      }

    } else {

      assert(hr->is_continues_humongous(), "Invalid humongous.");

    }

  } else {

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

  }

  return false;

}