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
25namespace art {
26
27class MemMap;
28
29namespace mirror {
30  class Object;
31}  // namespace mirror
32
33namespace gc {
34
35namespace space {
36  class ContinuousSpace;
37}  // namespace space
38
39class Heap;
40
41namespace accounting {
42
43template<size_t kAlignment> class SpaceBitmap;
44
45// Maintain a card table from the the write barrier. All writes of
46// non-null values to heap addresses should go through an entry in
47// WriteBarrier, and from there to here.
48class CardTable {
49 public:
50  static constexpr size_t kCardShift = 7;
51  static constexpr size_t kCardSize = 1 << kCardShift;
52  static constexpr uint8_t kCardClean = 0x0;
53  static constexpr uint8_t kCardDirty = 0x70;
54
55  static CardTable* Create(const uint8_t* heap_begin, size_t heap_capacity);
56  ~CardTable();
57
58  // Set the card associated with the given address to GC_CARD_DIRTY.
59  ALWAYS_INLINE void MarkCard(const void *addr) {
60    *CardFromAddr(addr) = kCardDirty;
61  }
62
63  // Is the object on a dirty card?
64  bool IsDirty(const mirror::Object* obj) const {
65    return GetCard(obj) == kCardDirty;
66  }
67
68  // Return the state of the card at an address.
69  uint8_t GetCard(const mirror::Object* obj) const {
70    return *CardFromAddr(obj);
71  }
72
73  // Visit and clear cards within memory range, only visits dirty cards.
74  template <typename Visitor>
75  void VisitClear(const void* start, const void* end, const Visitor& visitor) {
76    uint8_t* card_start = CardFromAddr(start);
77    uint8_t* card_end = CardFromAddr(end);
78    for (uint8_t* it = card_start; it != card_end; ++it) {
79      if (*it == kCardDirty) {
80        *it = kCardClean;
81        visitor(it);
82      }
83    }
84  }
85
86  // Returns a value that when added to a heap address >> GC_CARD_SHIFT will address the appropriate
87  // card table byte. For convenience this value is cached in every Thread
88  uint8_t* GetBiasedBegin() const {
89    return biased_begin_;
90  }
91
92  /*
93   * Visitor is expected to take in a card and return the new value. When a value is modified, the
94   * modify visitor is called.
95   * visitor: The visitor which modifies the cards. Returns the new value for a card given an old
96   * value.
97   * modified: Whenever the visitor modifies a card, this visitor is called on the card. Enables
98   * us to know which cards got cleared.
99   */
100  template <typename Visitor, typename ModifiedVisitor>
101  void ModifyCardsAtomic(uint8_t* scan_begin, uint8_t* scan_end, const Visitor& visitor,
102                         const ModifiedVisitor& modified);
103
104  // For every dirty at least minumum age between begin and end invoke the visitor with the
105  // specified argument. Returns how many cards the visitor was run on.
106  template <bool kClearCard, typename Visitor>
107  size_t Scan(SpaceBitmap<kObjectAlignment>* bitmap, uint8_t* scan_begin, uint8_t* scan_end,
108              const Visitor& visitor,
109              const uint8_t minimum_age = kCardDirty) const
110      REQUIRES(Locks::heap_bitmap_lock_)
111      SHARED_REQUIRES(Locks::mutator_lock_);
112
113  // Assertion used to check the given address is covered by the card table
114  void CheckAddrIsInCardTable(const uint8_t* addr) const;
115
116  // Resets all of the bytes in the card table to clean.
117  void ClearCardTable();
118
119  // Clear a range of cards that covers start to end, start and end must be aligned to kCardSize.
120  void ClearCardRange(uint8_t* start, uint8_t* end);
121
122  // Resets all of the bytes in the card table which do not map to the image space.
123  void ClearSpaceCards(space::ContinuousSpace* space);
124
125  // Returns the first address in the heap which maps to this card.
126  void* AddrFromCard(const uint8_t *card_addr) const ALWAYS_INLINE;
127
128  // Returns the address of the relevant byte in the card table, given an address on the heap.
129  uint8_t* CardFromAddr(const void *addr) const ALWAYS_INLINE;
130
131  bool AddrIsInCardTable(const void* addr) const;
132
133 private:
134  CardTable(MemMap* begin, uint8_t* biased_begin, size_t offset);
135
136  // Returns true iff the card table address is within the bounds of the card table.
137  bool IsValidCard(const uint8_t* card_addr) const ALWAYS_INLINE;
138
139  void CheckCardValid(uint8_t* 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  uint8_t* 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  DISALLOW_IMPLICIT_CONSTRUCTORS(CardTable);
153};
154
155}  // namespace accounting
156}  // namespace gc
157}  // namespace art
158
159#endif  // ART_RUNTIME_GC_ACCOUNTING_CARD_TABLE_H_
160