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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 "heap_bitmap.h"
     24 #include "gc/collector/mark_sweep.h"
     25 #include "gc/collector/mark_sweep-inl.h"
     26 #include "gc/collector/semi_space.h"
     27 #include "gc/heap.h"
     28 #include "gc/space/space.h"
     29 #include "mirror/object-inl.h"
     30 #include "mirror/class-inl.h"
     31 #include "mirror/object_array-inl.h"
     32 #include "space_bitmap-inl.h"
     33 #include "thread.h"
     34 
     35 namespace art {
     36 namespace gc {
     37 namespace accounting {
     38 
     39 class RememberedSetCardVisitor {
     40  public:
     41   explicit RememberedSetCardVisitor(RememberedSet::CardSet* const dirty_cards)
     42       : dirty_cards_(dirty_cards) {}
     43 
     44   void operator()(uint8_t* card, uint8_t expected_value, uint8_t new_value ATTRIBUTE_UNUSED) const {
     45     if (expected_value == CardTable::kCardDirty) {
     46       dirty_cards_->insert(card);
     47     }
     48   }
     49 
     50  private:
     51   RememberedSet::CardSet* const dirty_cards_;
     52 };
     53 
     54 void RememberedSet::ClearCards() {
     55   CardTable* card_table = GetHeap()->GetCardTable();
     56   RememberedSetCardVisitor card_visitor(&dirty_cards_);
     57   // Clear dirty cards in the space and insert them into the dirty card set.
     58   card_table->ModifyCardsAtomic(space_->Begin(), space_->End(), AgeCardVisitor(), card_visitor);
     59 }
     60 
     61 class RememberedSetReferenceVisitor {
     62  public:
     63   RememberedSetReferenceVisitor(space::ContinuousSpace* target_space,
     64                                 bool* const contains_reference_to_target_space,
     65                                 collector::GarbageCollector* collector)
     66       : collector_(collector), target_space_(target_space),
     67         contains_reference_to_target_space_(contains_reference_to_target_space) {}
     68 
     69   void operator()(mirror::Object* obj, MemberOffset offset, bool is_static ATTRIBUTE_UNUSED) const
     70       SHARED_REQUIRES(Locks::mutator_lock_) {
     71     DCHECK(obj != nullptr);
     72     mirror::HeapReference<mirror::Object>* ref_ptr = obj->GetFieldObjectReferenceAddr(offset);
     73     if (target_space_->HasAddress(ref_ptr->AsMirrorPtr())) {
     74       *contains_reference_to_target_space_ = true;
     75       collector_->MarkHeapReference(ref_ptr);
     76       DCHECK(!target_space_->HasAddress(ref_ptr->AsMirrorPtr()));
     77     }
     78   }
     79 
     80   void operator()(mirror::Class* klass, mirror::Reference* ref) const
     81       SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::heap_bitmap_lock_) {
     82     if (target_space_->HasAddress(ref->GetReferent())) {
     83       *contains_reference_to_target_space_ = true;
     84       collector_->DelayReferenceReferent(klass, ref);
     85     }
     86   }
     87 
     88   void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root) const
     89       SHARED_REQUIRES(Locks::mutator_lock_) {
     90     if (!root->IsNull()) {
     91       VisitRoot(root);
     92     }
     93   }
     94 
     95   void VisitRoot(mirror::CompressedReference<mirror::Object>* root) const
     96       SHARED_REQUIRES(Locks::mutator_lock_) {
     97     if (target_space_->HasAddress(root->AsMirrorPtr())) {
     98       *contains_reference_to_target_space_ = true;
     99       root->Assign(collector_->MarkObject(root->AsMirrorPtr()));
    100       DCHECK(!target_space_->HasAddress(root->AsMirrorPtr()));
    101     }
    102   }
    103 
    104  private:
    105   collector::GarbageCollector* const collector_;
    106   space::ContinuousSpace* const target_space_;
    107   bool* const contains_reference_to_target_space_;
    108 };
    109 
    110 class RememberedSetObjectVisitor {
    111  public:
    112   RememberedSetObjectVisitor(space::ContinuousSpace* target_space,
    113                              bool* const contains_reference_to_target_space,
    114                              collector::GarbageCollector* collector)
    115       : collector_(collector), target_space_(target_space),
    116         contains_reference_to_target_space_(contains_reference_to_target_space) {}
    117 
    118   void operator()(mirror::Object* obj) const REQUIRES(Locks::heap_bitmap_lock_)
    119       SHARED_REQUIRES(Locks::mutator_lock_) {
    120     RememberedSetReferenceVisitor visitor(target_space_, contains_reference_to_target_space_,
    121                                           collector_);
    122     obj->VisitReferences(visitor, visitor);
    123   }
    124 
    125  private:
    126   collector::GarbageCollector* const collector_;
    127   space::ContinuousSpace* const target_space_;
    128   bool* const contains_reference_to_target_space_;
    129 };
    130 
    131 void RememberedSet::UpdateAndMarkReferences(space::ContinuousSpace* target_space,
    132                                             collector::GarbageCollector* collector) {
    133   CardTable* card_table = heap_->GetCardTable();
    134   bool contains_reference_to_target_space = false;
    135   RememberedSetObjectVisitor obj_visitor(target_space, &contains_reference_to_target_space,
    136                                          collector);
    137   ContinuousSpaceBitmap* bitmap = space_->GetLiveBitmap();
    138   CardSet remove_card_set;
    139   for (uint8_t* const card_addr : dirty_cards_) {
    140     contains_reference_to_target_space = false;
    141     uintptr_t start = reinterpret_cast<uintptr_t>(card_table->AddrFromCard(card_addr));
    142     DCHECK(space_->HasAddress(reinterpret_cast<mirror::Object*>(start)));
    143     bitmap->VisitMarkedRange(start, start + CardTable::kCardSize, obj_visitor);
    144     if (!contains_reference_to_target_space) {
    145       // It was in the dirty card set, but it didn't actually contain
    146       // a reference to the target space. So, remove it from the dirty
    147       // card set so we won't have to scan it again (unless it gets
    148       // dirty again.)
    149       remove_card_set.insert(card_addr);
    150     }
    151   }
    152 
    153   // Remove the cards that didn't contain a reference to the target
    154   // space from the dirty card set.
    155   for (uint8_t* const card_addr : remove_card_set) {
    156     DCHECK(dirty_cards_.find(card_addr) != dirty_cards_.end());
    157     dirty_cards_.erase(card_addr);
    158   }
    159 }
    160 
    161 void RememberedSet::Dump(std::ostream& os) {
    162   CardTable* card_table = heap_->GetCardTable();
    163   os << "RememberedSet dirty cards: [";
    164   for (const uint8_t* card_addr : dirty_cards_) {
    165     auto start = reinterpret_cast<uintptr_t>(card_table->AddrFromCard(card_addr));
    166     auto end = start + CardTable::kCardSize;
    167     os << reinterpret_cast<void*>(start) << "-" << reinterpret_cast<void*>(end) << "\n";
    168   }
    169   os << "]";
    170 }
    171 
    172 void RememberedSet::AssertAllDirtyCardsAreWithinSpace() const {
    173   CardTable* card_table = heap_->GetCardTable();
    174   for (const uint8_t* card_addr : dirty_cards_) {
    175     auto start = reinterpret_cast<uint8_t*>(card_table->AddrFromCard(card_addr));
    176     auto end = start + CardTable::kCardSize;
    177     DCHECK_LE(space_->Begin(), start);
    178     DCHECK_LE(end, space_->Limit());
    179   }
    180 }
    181 
    182 }  // namespace accounting
    183 }  // namespace gc
    184 }  // namespace art
    185