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 "globals.h" 21 #include "locks.h" 22 #include "mem_map.h" 23 #include "UniquePtr.h" 24 25 namespace art { 26 27 namespace mirror { 28 class Object; 29 } // namespace mirror 30 31 namespace gc { 32 33 namespace space { 34 class ContinuousSpace; 35 } // namespace space 36 37 class Heap; 38 39 namespace accounting { 40 41 class SpaceBitmap; 42 43 // Maintain a card table from the the write barrier. All writes of 44 // non-NULL values to heap addresses should go through an entry in 45 // WriteBarrier, and from there to here. 46 class CardTable { 47 public: 48 static const size_t kCardShift = 7; 49 static const size_t kCardSize = (1 << kCardShift); 50 static const uint8_t kCardClean = 0x0; 51 static const uint8_t kCardDirty = 0x70; 52 53 static CardTable* Create(const byte* heap_begin, size_t heap_capacity); 54 55 // Set the card associated with the given address to GC_CARD_DIRTY. MarkCard(const void * addr)56 void MarkCard(const void *addr) { 57 byte* card_addr = CardFromAddr(addr); 58 *card_addr = kCardDirty; 59 } 60 61 // Is the object on a dirty card? IsDirty(const mirror::Object * obj)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. GetCard(const mirror::Object * obj)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> VisitClear(const void * start,const void * end,const Visitor & 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 GetBiasedBegin()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* bitmap, byte* scan_begin, byte* scan_end, const Visitor& visitor, 106 const byte minimum_age = kCardDirty) const 107 EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) 108 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 109 110 // Assertion used to check the given address is covered by the card table 111 void CheckAddrIsInCardTable(const byte* addr) const; 112 113 // Resets all of the bytes in the card table to clean. 114 void ClearCardTable(); 115 116 // Resets all of the bytes in the card table which do not map to the image space. 117 void ClearSpaceCards(space::ContinuousSpace* space); 118 119 // Returns the first address in the heap which maps to this card. 120 void* AddrFromCard(const byte *card_addr) const ALWAYS_INLINE; 121 122 // Returns the address of the relevant byte in the card table, given an address on the heap. 123 byte* CardFromAddr(const void *addr) const ALWAYS_INLINE; 124 125 bool AddrIsInCardTable(const void* addr) const; 126 127 private: 128 CardTable(MemMap* begin, byte* biased_begin, size_t offset); 129 130 // Returns true iff the card table address is within the bounds of the card table. IsValidCard(const byte * card_addr)131 bool IsValidCard(const byte* card_addr) const { 132 byte* begin = mem_map_->Begin() + offset_; 133 byte* end = mem_map_->End(); 134 return card_addr >= begin && card_addr < end; 135 } 136 137 void CheckCardValid(byte* card) const ALWAYS_INLINE; 138 139 // Verifies that all gray objects are on a dirty card. 140 void VerifyCardTable(); 141 142 // Mmapped pages for the card table 143 UniquePtr<MemMap> mem_map_; 144 // Value used to compute card table addresses from object addresses, see GetBiasedBegin 145 byte* const biased_begin_; 146 // Card table doesn't begin at the beginning of the mem_map_, instead it is displaced by offset 147 // to allow the byte value of biased_begin_ to equal GC_CARD_DIRTY 148 const size_t offset_; 149 }; 150 151 } // namespace accounting 152 } // namespace gc 153 } // namespace art 154 155 #endif // ART_RUNTIME_GC_ACCOUNTING_CARD_TABLE_H_ 156