1 /* 2 * Copyright (C) 2011 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 #ifndef ART_RUNTIME_GC_ACCOUNTING_CARD_TABLE_H_ 18 #define ART_RUNTIME_GC_ACCOUNTING_CARD_TABLE_H_ 19 20 #include <memory> 21 22 #include "base/mutex.h" 23 #include "globals.h" 24 #include "mem_map.h" 25 26 namespace art { 27 28 namespace mirror { 29 class Object; 30 } // namespace mirror 31 32 namespace gc { 33 34 namespace space { 35 class ContinuousSpace; 36 } // namespace space 37 38 class Heap; 39 40 namespace accounting { 41 42 template<size_t kAlignment> class SpaceBitmap; 43 44 // Maintain a card table from the the write barrier. All writes of 45 // non-NULL values to heap addresses should go through an entry in 46 // WriteBarrier, and from there to here. 47 class CardTable { 48 public: 49 static constexpr size_t kCardShift = 7; 50 static constexpr size_t kCardSize = 1 << kCardShift; 51 static constexpr uint8_t kCardClean = 0x0; 52 static constexpr uint8_t kCardDirty = 0x70; 53 54 static CardTable* Create(const byte* heap_begin, size_t heap_capacity); 55 56 // Set the card associated with the given address to GC_CARD_DIRTY. 57 ALWAYS_INLINE void MarkCard(const void *addr) { 58 *CardFromAddr(addr) = kCardDirty; 59 } 60 61 // Is the object on a dirty card? 62 bool IsDirty(const mirror::Object* obj) const { 63 return GetCard(obj) == kCardDirty; 64 } 65 66 // Return the state of the card at an address. 67 byte GetCard(const mirror::Object* obj) const { 68 return *CardFromAddr(obj); 69 } 70 71 // Visit and clear cards within memory range, only visits dirty cards. 72 template <typename Visitor> 73 void VisitClear(const void* start, const void* end, const Visitor& visitor) { 74 byte* card_start = CardFromAddr(start); 75 byte* card_end = CardFromAddr(end); 76 for (byte* it = card_start; it != card_end; ++it) { 77 if (*it == kCardDirty) { 78 *it = kCardClean; 79 visitor(it); 80 } 81 } 82 } 83 84 // Returns a value that when added to a heap address >> GC_CARD_SHIFT will address the appropriate 85 // card table byte. For convenience this value is cached in every Thread 86 byte* GetBiasedBegin() const { 87 return biased_begin_; 88 } 89 90 /* 91 * Visitor is expected to take in a card and return the new value. When a value is modified, the 92 * modify visitor is called. 93 * visitor: The visitor which modifies the cards. Returns the new value for a card given an old 94 * value. 95 * modified: Whenever the visitor modifies a card, this visitor is called on the card. Enables 96 * us to know which cards got cleared. 97 */ 98 template <typename Visitor, typename ModifiedVisitor> 99 void ModifyCardsAtomic(byte* scan_begin, byte* scan_end, const Visitor& visitor, 100 const ModifiedVisitor& modified); 101 102 // For every dirty at least minumum age between begin and end invoke the visitor with the 103 // specified argument. Returns how many cards the visitor was run on. 104 template <typename Visitor> 105 size_t Scan(SpaceBitmap<kObjectAlignment>* bitmap, byte* scan_begin, byte* scan_end, 106 const Visitor& visitor, 107 const byte minimum_age = kCardDirty) const 108 EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) 109 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 110 111 // Assertion used to check the given address is covered by the card table 112 void CheckAddrIsInCardTable(const byte* addr) const; 113 114 // Resets all of the bytes in the card table to clean. 115 void ClearCardTable(); 116 117 // Resets all of the bytes in the card table which do not map to the image space. 118 void ClearSpaceCards(space::ContinuousSpace* space); 119 120 // Returns the first address in the heap which maps to this card. 121 void* AddrFromCard(const byte *card_addr) const ALWAYS_INLINE; 122 123 // Returns the address of the relevant byte in the card table, given an address on the heap. 124 byte* CardFromAddr(const void *addr) const ALWAYS_INLINE; 125 126 bool AddrIsInCardTable(const void* addr) const; 127 128 private: 129 CardTable(MemMap* begin, byte* biased_begin, size_t offset); 130 131 // Returns true iff the card table address is within the bounds of the card table. 132 bool IsValidCard(const byte* card_addr) const { 133 byte* begin = mem_map_->Begin() + offset_; 134 byte* end = mem_map_->End(); 135 return card_addr >= begin && card_addr < end; 136 } 137 138 void CheckCardValid(byte* card) const ALWAYS_INLINE; 139 140 // Verifies that all gray objects are on a dirty card. 141 void VerifyCardTable(); 142 143 // Mmapped pages for the card table 144 std::unique_ptr<MemMap> mem_map_; 145 // Value used to compute card table addresses from object addresses, see GetBiasedBegin 146 byte* const biased_begin_; 147 // Card table doesn't begin at the beginning of the mem_map_, instead it is displaced by offset 148 // to allow the byte value of biased_begin_ to equal GC_CARD_DIRTY 149 const size_t offset_; 150 }; 151 152 } // namespace accounting 153 } // namespace gc 154 } // namespace art 155 156 #endif // ART_RUNTIME_GC_ACCOUNTING_CARD_TABLE_H_ 157
