/*

 * Copyright (c) 2001, 2012, 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 "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

  TraceTime tm("phase 1", G1Log::fine() && 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(/* 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 */

                                            NULL, /* old_proxy_set */

                                            &_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;

  }

};

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();

  TraceTime tm("phase 2", G1Log::fine() && Verbose, true, gclog_or_tty);

  GenMarkSweep::trace("2");

  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

  TraceTime tm("phase 3", G1Log::fine() && 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();

  TraceTime tm("phase 4", G1Log::fine() && Verbose, true, gclog_or_tty);

  GenMarkSweep::trace("4");

  pg->compact();

  G1SpaceCompactClosure blk;

  g1h->heap_region_iterate(&blk);

}