V8 API Reference, 7.2.502.16 (for Deno 0.2.4)
remembered-set.h
1 // Copyright 2016 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #ifndef V8_HEAP_REMEMBERED_SET_H_
6 #define V8_HEAP_REMEMBERED_SET_H_
7 
8 #include "src/heap/heap.h"
9 #include "src/heap/slot-set.h"
10 #include "src/heap/spaces.h"
11 #include "src/reloc-info.h"
12 #include "src/v8memory.h"
13 
14 namespace v8 {
15 namespace internal {
16 
17 enum RememberedSetIterationMode { SYNCHRONIZED, NON_SYNCHRONIZED };
18 
19 // TODO(ulan): Investigate performance of de-templatizing this class.
20 template <RememberedSetType type>
21 class RememberedSet : public AllStatic {
22  public:
23  // Given a page and a slot in that page, this function adds the slot to the
24  // remembered set.
25  template <AccessMode access_mode = AccessMode::ATOMIC>
26  static void Insert(MemoryChunk* chunk, Address slot_addr) {
27  DCHECK(chunk->Contains(slot_addr));
28  SlotSet* slot_set = chunk->slot_set<type, access_mode>();
29  if (slot_set == nullptr) {
30  slot_set = chunk->AllocateSlotSet<type>();
31  }
32  uintptr_t offset = slot_addr - chunk->address();
33  slot_set[offset / Page::kPageSize].Insert<access_mode>(offset %
34  Page::kPageSize);
35  }
36 
37  // Given a page and a slot in that page, this function returns true if
38  // the remembered set contains the slot.
39  static bool Contains(MemoryChunk* chunk, Address slot_addr) {
40  DCHECK(chunk->Contains(slot_addr));
41  SlotSet* slot_set = chunk->slot_set<type>();
42  if (slot_set == nullptr) {
43  return false;
44  }
45  uintptr_t offset = slot_addr - chunk->address();
46  return slot_set[offset / Page::kPageSize].Contains(offset %
47  Page::kPageSize);
48  }
49 
50  // Given a page and a slot in that page, this function removes the slot from
51  // the remembered set.
52  // If the slot was never added, then the function does nothing.
53  static void Remove(MemoryChunk* chunk, Address slot_addr) {
54  DCHECK(chunk->Contains(slot_addr));
55  SlotSet* slot_set = chunk->slot_set<type>();
56  if (slot_set != nullptr) {
57  uintptr_t offset = slot_addr - chunk->address();
58  slot_set[offset / Page::kPageSize].Remove(offset % Page::kPageSize);
59  }
60  }
61 
62  // Given a page and a range of slots in that page, this function removes the
63  // slots from the remembered set.
64  static void RemoveRange(MemoryChunk* chunk, Address start, Address end,
65  SlotSet::EmptyBucketMode mode) {
66  SlotSet* slot_set = chunk->slot_set<type>();
67  if (slot_set != nullptr) {
68  uintptr_t start_offset = start - chunk->address();
69  uintptr_t end_offset = end - chunk->address();
70  DCHECK_LT(start_offset, end_offset);
71  if (end_offset < static_cast<uintptr_t>(Page::kPageSize)) {
72  slot_set->RemoveRange(static_cast<int>(start_offset),
73  static_cast<int>(end_offset), mode);
74  } else {
75  // The large page has multiple slot sets.
76  // Compute slot set indicies for the range [start_offset, end_offset).
77  int start_chunk = static_cast<int>(start_offset / Page::kPageSize);
78  int end_chunk = static_cast<int>((end_offset - 1) / Page::kPageSize);
79  int offset_in_start_chunk =
80  static_cast<int>(start_offset % Page::kPageSize);
81  // Note that using end_offset % Page::kPageSize would be incorrect
82  // because end_offset is one beyond the last slot to clear.
83  int offset_in_end_chunk = static_cast<int>(
84  end_offset - static_cast<uintptr_t>(end_chunk) * Page::kPageSize);
85  if (start_chunk == end_chunk) {
86  slot_set[start_chunk].RemoveRange(offset_in_start_chunk,
87  offset_in_end_chunk, mode);
88  } else {
89  // Clear all slots from start_offset to the end of first chunk.
90  slot_set[start_chunk].RemoveRange(offset_in_start_chunk,
91  Page::kPageSize, mode);
92  // Clear all slots in intermediate chunks.
93  for (int i = start_chunk + 1; i < end_chunk; i++) {
94  slot_set[i].RemoveRange(0, Page::kPageSize, mode);
95  }
96  // Clear slots from the beginning of the last page to end_offset.
97  slot_set[end_chunk].RemoveRange(0, offset_in_end_chunk, mode);
98  }
99  }
100  }
101  }
102 
103  // Iterates and filters the remembered set with the given callback.
104  // The callback should take (Address slot) and return SlotCallbackResult.
105  template <typename Callback>
106  static void Iterate(Heap* heap, RememberedSetIterationMode mode,
107  Callback callback) {
108  IterateMemoryChunks(heap, [mode, callback](MemoryChunk* chunk) {
109  if (mode == SYNCHRONIZED) chunk->mutex()->Lock();
110  Iterate(chunk, callback);
111  if (mode == SYNCHRONIZED) chunk->mutex()->Unlock();
112  });
113  }
114 
115  // Iterates over all memory chunks that contains non-empty slot sets.
116  // The callback should take (MemoryChunk* chunk) and return void.
117  template <typename Callback>
118  static void IterateMemoryChunks(Heap* heap, Callback callback) {
120  MemoryChunk* chunk;
121  while ((chunk = it.next()) != nullptr) {
122  SlotSet* slots = chunk->slot_set<type>();
123  TypedSlotSet* typed_slots = chunk->typed_slot_set<type>();
124  if (slots != nullptr || typed_slots != nullptr ||
125  chunk->invalidated_slots() != nullptr) {
126  callback(chunk);
127  }
128  }
129  }
130 
131  // Iterates and filters the remembered set in the given memory chunk with
132  // the given callback. The callback should take (Address slot) and return
133  // SlotCallbackResult.
134  //
135  // Notice that |mode| can only be of FREE* or PREFREE* if there are no other
136  // threads concurrently inserting slots.
137  template <typename Callback>
138  static void Iterate(MemoryChunk* chunk, Callback callback,
139  SlotSet::EmptyBucketMode mode) {
140  SlotSet* slots = chunk->slot_set<type>();
141  if (slots != nullptr) {
142  size_t pages = (chunk->size() + Page::kPageSize - 1) / Page::kPageSize;
143  int new_count = 0;
144  for (size_t page = 0; page < pages; page++) {
145  new_count += slots[page].Iterate(callback, mode);
146  }
147  // Only old-to-old slot sets are released eagerly. Old-new-slot sets are
148  // released by the sweeper threads.
149  if (type == OLD_TO_OLD && new_count == 0) {
150  chunk->ReleaseSlotSet<OLD_TO_OLD>();
151  }
152  }
153  }
154 
155  static int NumberOfPreFreedEmptyBuckets(MemoryChunk* chunk) {
156  DCHECK(type == OLD_TO_NEW);
157  int result = 0;
158  SlotSet* slots = chunk->slot_set<type>();
159  if (slots != nullptr) {
160  size_t pages = (chunk->size() + Page::kPageSize - 1) / Page::kPageSize;
161  for (size_t page = 0; page < pages; page++) {
162  result += slots[page].NumberOfPreFreedEmptyBuckets();
163  }
164  }
165  return result;
166  }
167 
168  static void PreFreeEmptyBuckets(MemoryChunk* chunk) {
169  DCHECK(type == OLD_TO_NEW);
170  SlotSet* slots = chunk->slot_set<type>();
171  if (slots != nullptr) {
172  size_t pages = (chunk->size() + Page::kPageSize - 1) / Page::kPageSize;
173  for (size_t page = 0; page < pages; page++) {
174  slots[page].PreFreeEmptyBuckets();
175  }
176  }
177  }
178 
179  static void FreeEmptyBuckets(MemoryChunk* chunk) {
180  DCHECK(type == OLD_TO_NEW);
181  SlotSet* slots = chunk->slot_set<type>();
182  if (slots != nullptr) {
183  size_t pages = (chunk->size() + Page::kPageSize - 1) / Page::kPageSize;
184  for (size_t page = 0; page < pages; page++) {
185  slots[page].FreeEmptyBuckets();
186  slots[page].FreeToBeFreedBuckets();
187  }
188  }
189  }
190 
191  // Given a page and a typed slot in that page, this function adds the slot
192  // to the remembered set.
193  static void InsertTyped(Page* page, Address host_addr, SlotType slot_type,
194  Address slot_addr) {
195  TypedSlotSet* slot_set = page->typed_slot_set<type>();
196  if (slot_set == nullptr) {
197  slot_set = page->AllocateTypedSlotSet<type>();
198  }
199  if (host_addr == kNullAddress) {
200  host_addr = page->address();
201  }
202  uintptr_t offset = slot_addr - page->address();
203  uintptr_t host_offset = host_addr - page->address();
204  DCHECK_LT(offset, static_cast<uintptr_t>(TypedSlotSet::kMaxOffset));
205  DCHECK_LT(host_offset, static_cast<uintptr_t>(TypedSlotSet::kMaxOffset));
206  slot_set->Insert(slot_type, static_cast<uint32_t>(host_offset),
207  static_cast<uint32_t>(offset));
208  }
209 
210  // Given a page and a range of typed slots in that page, this function removes
211  // the slots from the remembered set.
212  static void RemoveRangeTyped(MemoryChunk* page, Address start, Address end) {
213  TypedSlotSet* slots = page->typed_slot_set<type>();
214  if (slots != nullptr) {
215  slots->Iterate(
216  [start, end](SlotType slot_type, Address host_addr,
217  Address slot_addr) {
218  return start <= slot_addr && slot_addr < end ? REMOVE_SLOT
219  : KEEP_SLOT;
220  },
221  TypedSlotSet::PREFREE_EMPTY_CHUNKS);
222  }
223  }
224 
225  // Iterates and filters the remembered set with the given callback.
226  // The callback should take (SlotType slot_type, SlotAddress slot) and return
227  // SlotCallbackResult.
228  template <typename Callback>
229  static void IterateTyped(Heap* heap, RememberedSetIterationMode mode,
230  Callback callback) {
231  IterateMemoryChunks(heap, [mode, callback](MemoryChunk* chunk) {
232  if (mode == SYNCHRONIZED) chunk->mutex()->Lock();
233  IterateTyped(chunk, callback);
234  if (mode == SYNCHRONIZED) chunk->mutex()->Unlock();
235  });
236  }
237 
238  // Iterates and filters typed old to old pointers in the given memory chunk
239  // with the given callback. The callback should take (SlotType slot_type,
240  // Address slot_addr) and return SlotCallbackResult.
241  template <typename Callback>
242  static void IterateTyped(MemoryChunk* chunk, Callback callback) {
243  TypedSlotSet* slots = chunk->typed_slot_set<type>();
244  if (slots != nullptr) {
245  int new_count = slots->Iterate(callback, TypedSlotSet::KEEP_EMPTY_CHUNKS);
246  if (new_count == 0) {
247  chunk->ReleaseTypedSlotSet<type>();
248  }
249  }
250  }
251 
252  // Clear all old to old slots from the remembered set.
253  static void ClearAll(Heap* heap) {
254  STATIC_ASSERT(type == OLD_TO_OLD);
256  MemoryChunk* chunk;
257  while ((chunk = it.next()) != nullptr) {
258  chunk->ReleaseSlotSet<OLD_TO_OLD>();
259  chunk->ReleaseTypedSlotSet<OLD_TO_OLD>();
260  chunk->ReleaseInvalidatedSlots();
261  }
262  }
263 
264  private:
265  static bool IsValidSlot(Heap* heap, MemoryChunk* chunk, ObjectSlot slot);
266 };
267 
269  public:
270  // Updates a code entry slot using an untyped slot callback.
271  // The callback accepts MaybeObjectSlot and returns SlotCallbackResult.
272  template <typename Callback>
273  static SlotCallbackResult UpdateCodeEntry(Address entry_address,
274  Callback callback) {
275  Object* code = Code::GetObjectFromEntryAddress(entry_address);
276  Object* old_code = code;
277  SlotCallbackResult result = callback(MaybeObjectSlot(&code));
278  DCHECK(!HasWeakHeapObjectTag(code));
279  if (code != old_code) {
280  Memory<Address>(entry_address) = Code::cast(code)->entry();
281  }
282  return result;
283  }
284 
285  // Updates a code target slot using an untyped slot callback.
286  // The callback accepts MaybeObjectSlot and returns SlotCallbackResult.
287  template <typename Callback>
288  static SlotCallbackResult UpdateCodeTarget(RelocInfo* rinfo,
289  Callback callback) {
290  DCHECK(RelocInfo::IsCodeTargetMode(rinfo->rmode()));
291  Code old_target = Code::GetCodeFromTargetAddress(rinfo->target_address());
292  Object* new_target = old_target;
293  SlotCallbackResult result = callback(MaybeObjectSlot(&new_target));
294  DCHECK(!HasWeakHeapObjectTag(new_target));
295  if (new_target != old_target) {
296  rinfo->set_target_address(
297  Code::cast(new_target)->raw_instruction_start());
298  }
299  return result;
300  }
301 
302  // Updates an embedded pointer slot using an untyped slot callback.
303  // The callback accepts MaybeObjectSlot and returns SlotCallbackResult.
304  template <typename Callback>
305  static SlotCallbackResult UpdateEmbeddedPointer(Heap* heap, RelocInfo* rinfo,
306  Callback callback) {
307  DCHECK(rinfo->rmode() == RelocInfo::EMBEDDED_OBJECT);
308  HeapObject* old_target = rinfo->target_object();
309  Object* new_target = old_target;
310  SlotCallbackResult result = callback(MaybeObjectSlot(&new_target));
311  DCHECK(!HasWeakHeapObjectTag(new_target));
312  if (new_target != old_target) {
313  rinfo->set_target_object(heap, HeapObject::cast(new_target));
314  }
315  return result;
316  }
317 
318  // Updates a typed slot using an untyped slot callback.
319  // The callback accepts MaybeObjectSlot and returns SlotCallbackResult.
320  template <typename Callback>
321  static SlotCallbackResult UpdateTypedSlot(Heap* heap, SlotType slot_type,
322  Address addr, Callback callback) {
323  switch (slot_type) {
324  case CODE_TARGET_SLOT: {
325  RelocInfo rinfo(addr, RelocInfo::CODE_TARGET, 0, Code());
326  return UpdateCodeTarget(&rinfo, callback);
327  }
328  case CODE_ENTRY_SLOT: {
329  return UpdateCodeEntry(addr, callback);
330  }
331  case EMBEDDED_OBJECT_SLOT: {
332  RelocInfo rinfo(addr, RelocInfo::EMBEDDED_OBJECT, 0, Code());
333  return UpdateEmbeddedPointer(heap, &rinfo, callback);
334  }
335  case OBJECT_SLOT: {
336  return callback(MaybeObjectSlot(addr));
337  }
338  case CLEARED_SLOT:
339  break;
340  }
341  UNREACHABLE();
342  }
343 };
344 
345 inline SlotType SlotTypeForRelocInfoMode(RelocInfo::Mode rmode) {
346  if (RelocInfo::IsCodeTargetMode(rmode)) {
347  return CODE_TARGET_SLOT;
348  } else if (RelocInfo::IsEmbeddedObject(rmode)) {
349  return EMBEDDED_OBJECT_SLOT;
350  }
351  UNREACHABLE();
352 }
353 
354 } // namespace internal
355 } // namespace v8
356 
357 #endif // V8_HEAP_REMEMBERED_SET_H_
Definition: libplatform.h:13