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      1 /*
      2  * Copyright (C) 2014 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include "remembered_set.h"
     18 
     19 #include <memory>
     20 
     21 #include "base/stl_util.h"
     22 #include "card_table-inl.h"
     23 #include "gc/collector/mark_sweep-inl.h"
     24 #include "gc/collector/mark_sweep.h"
     25 #include "gc/collector/semi_space.h"
     26 #include "gc/heap.h"
     27 #include "gc/space/space.h"
     28 #include "heap_bitmap.h"
     29 #include "mirror/class-inl.h"
     30 #include "mirror/object-inl.h"
     31 #include "mirror/object-refvisitor-inl.h"
     32 #include "mirror/object_array-inl.h"
     33 #include "space_bitmap-inl.h"
     34 #include "thread.h"
     35 
     36 namespace art {
     37 namespace gc {
     38 namespace accounting {
     39 
     40 class RememberedSetCardVisitor {
     41  public:
     42   explicit RememberedSetCardVisitor(RememberedSet::CardSet* const dirty_cards)
     43       : dirty_cards_(dirty_cards) {}
     44 
     45   void operator()(uint8_t* card, uint8_t expected_value, uint8_t new_value ATTRIBUTE_UNUSED) const {
     46     if (expected_value == CardTable::kCardDirty) {
     47       dirty_cards_->insert(card);
     48     }
     49   }
     50 
     51  private:
     52   RememberedSet::CardSet* const dirty_cards_;
     53 };
     54 
     55 void RememberedSet::ClearCards() {
     56   CardTable* card_table = GetHeap()->GetCardTable();
     57   RememberedSetCardVisitor card_visitor(&dirty_cards_);
     58   // Clear dirty cards in the space and insert them into the dirty card set.
     59   card_table->ModifyCardsAtomic(space_->Begin(), space_->End(), AgeCardVisitor(), card_visitor);
     60 }
     61 
     62 class RememberedSetReferenceVisitor {
     63  public:
     64   RememberedSetReferenceVisitor(space::ContinuousSpace* target_space,
     65                                 bool* const contains_reference_to_target_space,
     66                                 collector::GarbageCollector* collector)
     67       : collector_(collector), target_space_(target_space),
     68         contains_reference_to_target_space_(contains_reference_to_target_space) {}
     69 
     70   void operator()(ObjPtr<mirror::Object> obj,
     71                   MemberOffset offset,
     72                   bool is_static ATTRIBUTE_UNUSED) const
     73       REQUIRES_SHARED(Locks::mutator_lock_) {
     74     DCHECK(obj != nullptr);
     75     mirror::HeapReference<mirror::Object>* ref_ptr = obj->GetFieldObjectReferenceAddr(offset);
     76     if (target_space_->HasAddress(ref_ptr->AsMirrorPtr())) {
     77       *contains_reference_to_target_space_ = true;
     78       collector_->MarkHeapReference(ref_ptr, /*do_atomic_update*/ false);
     79       DCHECK(!target_space_->HasAddress(ref_ptr->AsMirrorPtr()));
     80     }
     81   }
     82 
     83   void operator()(ObjPtr<mirror::Class> klass, ObjPtr<mirror::Reference> ref) const
     84       REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::heap_bitmap_lock_) {
     85     if (target_space_->HasAddress(ref->GetReferent())) {
     86       *contains_reference_to_target_space_ = true;
     87       collector_->DelayReferenceReferent(klass, ref);
     88     }
     89   }
     90 
     91   void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root) const
     92       REQUIRES_SHARED(Locks::mutator_lock_) {
     93     if (!root->IsNull()) {
     94       VisitRoot(root);
     95     }
     96   }
     97 
     98   void VisitRoot(mirror::CompressedReference<mirror::Object>* root) const
     99       REQUIRES_SHARED(Locks::mutator_lock_) {
    100     if (target_space_->HasAddress(root->AsMirrorPtr())) {
    101       *contains_reference_to_target_space_ = true;
    102       root->Assign(collector_->MarkObject(root->AsMirrorPtr()));
    103       DCHECK(!target_space_->HasAddress(root->AsMirrorPtr()));
    104     }
    105   }
    106 
    107  private:
    108   collector::GarbageCollector* const collector_;
    109   space::ContinuousSpace* const target_space_;
    110   bool* const contains_reference_to_target_space_;
    111 };
    112 
    113 class RememberedSetObjectVisitor {
    114  public:
    115   RememberedSetObjectVisitor(space::ContinuousSpace* target_space,
    116                              bool* const contains_reference_to_target_space,
    117                              collector::GarbageCollector* collector)
    118       : collector_(collector), target_space_(target_space),
    119         contains_reference_to_target_space_(contains_reference_to_target_space) {}
    120 
    121   void operator()(ObjPtr<mirror::Object> obj) const REQUIRES(Locks::heap_bitmap_lock_)
    122       REQUIRES_SHARED(Locks::mutator_lock_) {
    123     RememberedSetReferenceVisitor visitor(target_space_, contains_reference_to_target_space_,
    124                                           collector_);
    125     obj->VisitReferences(visitor, visitor);
    126   }
    127 
    128  private:
    129   collector::GarbageCollector* const collector_;
    130   space::ContinuousSpace* const target_space_;
    131   bool* const contains_reference_to_target_space_;
    132 };
    133 
    134 void RememberedSet::UpdateAndMarkReferences(space::ContinuousSpace* target_space,
    135                                             collector::GarbageCollector* collector) {
    136   CardTable* card_table = heap_->GetCardTable();
    137   bool contains_reference_to_target_space = false;
    138   RememberedSetObjectVisitor obj_visitor(target_space, &contains_reference_to_target_space,
    139                                          collector);
    140   ContinuousSpaceBitmap* bitmap = space_->GetLiveBitmap();
    141   CardSet remove_card_set;
    142   for (uint8_t* const card_addr : dirty_cards_) {
    143     contains_reference_to_target_space = false;
    144     uintptr_t start = reinterpret_cast<uintptr_t>(card_table->AddrFromCard(card_addr));
    145     DCHECK(space_->HasAddress(reinterpret_cast<mirror::Object*>(start)));
    146     bitmap->VisitMarkedRange(start, start + CardTable::kCardSize, obj_visitor);
    147     if (!contains_reference_to_target_space) {
    148       // It was in the dirty card set, but it didn't actually contain
    149       // a reference to the target space. So, remove it from the dirty
    150       // card set so we won't have to scan it again (unless it gets
    151       // dirty again.)
    152       remove_card_set.insert(card_addr);
    153     }
    154   }
    155 
    156   // Remove the cards that didn't contain a reference to the target
    157   // space from the dirty card set.
    158   for (uint8_t* const card_addr : remove_card_set) {
    159     DCHECK(dirty_cards_.find(card_addr) != dirty_cards_.end());
    160     dirty_cards_.erase(card_addr);
    161   }
    162 }
    163 
    164 void RememberedSet::Dump(std::ostream& os) {
    165   CardTable* card_table = heap_->GetCardTable();
    166   os << "RememberedSet dirty cards: [";
    167   for (const uint8_t* card_addr : dirty_cards_) {
    168     auto start = reinterpret_cast<uintptr_t>(card_table->AddrFromCard(card_addr));
    169     auto end = start + CardTable::kCardSize;
    170     os << reinterpret_cast<void*>(start) << "-" << reinterpret_cast<void*>(end) << "\n";
    171   }
    172   os << "]";
    173 }
    174 
    175 void RememberedSet::AssertAllDirtyCardsAreWithinSpace() const {
    176   CardTable* card_table = heap_->GetCardTable();
    177   for (const uint8_t* card_addr : dirty_cards_) {
    178     auto start = reinterpret_cast<uint8_t*>(card_table->AddrFromCard(card_addr));
    179     auto end = start + CardTable::kCardSize;
    180     DCHECK_LE(space_->Begin(), start);
    181     DCHECK_LE(end, space_->Limit());
    182   }
    183 }
    184 
    185 }  // namespace accounting
    186 }  // namespace gc
    187 }  // namespace art
    188