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. MarkCard(const void * addr)57 void MarkCard(const void *addr) { 58 byte* card_addr = CardFromAddr(addr); 59 *card_addr = kCardDirty; 60 } 61 62 // Is the object on a dirty card? IsDirty(const mirror::Object * obj)63 bool IsDirty(const mirror::Object* obj) const { 64 return GetCard(obj) == kCardDirty; 65 } 66 67 // Return the state of the card at an address. GetCard(const mirror::Object * obj)68 byte GetCard(const mirror::Object* obj) const { 69 return *CardFromAddr(obj); 70 } 71 72 // Visit and clear cards within memory range, only visits dirty cards. 73 template <typename Visitor> VisitClear(const void * start,const void * end,const Visitor & visitor)74 void VisitClear(const void* start, const void* end, const Visitor& visitor) { 75 byte* card_start = CardFromAddr(start); 76 byte* card_end = CardFromAddr(end); 77 for (byte* it = card_start; it != card_end; ++it) { 78 if (*it == kCardDirty) { 79 *it = kCardClean; 80 visitor(it); 81 } 82 } 83 } 84 85 // Returns a value that when added to a heap address >> GC_CARD_SHIFT will address the appropriate 86 // card table byte. For convenience this value is cached in every Thread GetBiasedBegin()87 byte* GetBiasedBegin() const { 88 return biased_begin_; 89 } 90 91 /* 92 * Visitor is expected to take in a card and return the new value. When a value is modified, the 93 * modify visitor is called. 94 * visitor: The visitor which modifies the cards. Returns the new value for a card given an old 95 * value. 96 * modified: Whenever the visitor modifies a card, this visitor is called on the card. Enables 97 * us to know which cards got cleared. 98 */ 99 template <typename Visitor, typename ModifiedVisitor> 100 void ModifyCardsAtomic(byte* scan_begin, byte* scan_end, const Visitor& visitor, 101 const ModifiedVisitor& modified); 102 103 // For every dirty at least minumum age between begin and end invoke the visitor with the 104 // specified argument. Returns how many cards the visitor was run on. 105 template <typename Visitor> 106 size_t Scan(SpaceBitmap<kObjectAlignment>* bitmap, byte* scan_begin, byte* scan_end, 107 const Visitor& visitor, 108 const byte minimum_age = kCardDirty) const 109 EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) 110 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 111 112 // Assertion used to check the given address is covered by the card table 113 void CheckAddrIsInCardTable(const byte* addr) const; 114 115 // Resets all of the bytes in the card table to clean. 116 void ClearCardTable(); 117 118 // Resets all of the bytes in the card table which do not map to the image space. 119 void ClearSpaceCards(space::ContinuousSpace* space); 120 121 // Returns the first address in the heap which maps to this card. 122 void* AddrFromCard(const byte *card_addr) const ALWAYS_INLINE; 123 124 // Returns the address of the relevant byte in the card table, given an address on the heap. 125 byte* CardFromAddr(const void *addr) const ALWAYS_INLINE; 126 127 bool AddrIsInCardTable(const void* addr) const; 128 129 private: 130 CardTable(MemMap* begin, byte* biased_begin, size_t offset); 131 132 // Returns true iff the card table address is within the bounds of the card table. IsValidCard(const byte * card_addr)133 bool IsValidCard(const byte* card_addr) const { 134 byte* begin = mem_map_->Begin() + offset_; 135 byte* end = mem_map_->End(); 136 return card_addr >= begin && card_addr < end; 137 } 138 139 void CheckCardValid(byte* card) const ALWAYS_INLINE; 140 141 // Verifies that all gray objects are on a dirty card. 142 void VerifyCardTable(); 143 144 // Mmapped pages for the card table 145 std::unique_ptr<MemMap> mem_map_; 146 // Value used to compute card table addresses from object addresses, see GetBiasedBegin 147 byte* const biased_begin_; 148 // Card table doesn't begin at the beginning of the mem_map_, instead it is displaced by offset 149 // to allow the byte value of biased_begin_ to equal GC_CARD_DIRTY 150 const size_t offset_; 151 }; 152 153 } // namespace accounting 154 } // namespace gc 155 } // namespace art 156 157 #endif // ART_RUNTIME_GC_ACCOUNTING_CARD_TABLE_H_ 158