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// Copyright 2016 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_HEAP_REMEMBERED_SET_H_
#define V8_HEAP_REMEMBERED_SET_H_
#include "src/codegen/reloc-info.h"
#include "src/common/v8memory.h"
#include "src/heap/heap.h"
#include "src/heap/slot-set.h"
#include "src/heap/spaces.h"
namespace v8 {
namespace internal {
enum RememberedSetIterationMode { SYNCHRONIZED, NON_SYNCHRONIZED };
// TODO(ulan): Investigate performance of de-templatizing this class.
template <RememberedSetType type>
class RememberedSet : public AllStatic {
public:
// Given a page and a slot in that page, this function adds the slot to the
// remembered set.
template <AccessMode access_mode = AccessMode::ATOMIC>
static void Insert(MemoryChunk* chunk, Address slot_addr) {
DCHECK(chunk->Contains(slot_addr));
SlotSet* slot_set = chunk->slot_set<type, access_mode>();
if (slot_set == nullptr) {
slot_set = chunk->AllocateSlotSet<type>();
}
uintptr_t offset = slot_addr - chunk->address();
slot_set[offset / Page::kPageSize].Insert<access_mode>(offset %
Page::kPageSize);
}
// Given a page and a slot in that page, this function returns true if
// the remembered set contains the slot.
static bool Contains(MemoryChunk* chunk, Address slot_addr) {
DCHECK(chunk->Contains(slot_addr));
SlotSet* slot_set = chunk->slot_set<type>();
if (slot_set == nullptr) {
return false;
}
uintptr_t offset = slot_addr - chunk->address();
return slot_set[offset / Page::kPageSize].Contains(offset %
Page::kPageSize);
}
// Given a page and a slot in that page, this function removes the slot from
// the remembered set.
// If the slot was never added, then the function does nothing.
static void Remove(MemoryChunk* chunk, Address slot_addr) {
DCHECK(chunk->Contains(slot_addr));
SlotSet* slot_set = chunk->slot_set<type>();
if (slot_set != nullptr) {
uintptr_t offset = slot_addr - chunk->address();
slot_set[offset / Page::kPageSize].Remove(offset % Page::kPageSize);
}
}
// Given a page and a range of slots in that page, this function removes the
// slots from the remembered set.
static void RemoveRange(MemoryChunk* chunk, Address start, Address end,
SlotSet::EmptyBucketMode mode) {
SlotSet* slot_set = chunk->slot_set<type>();
if (slot_set != nullptr) {
uintptr_t start_offset = start - chunk->address();
uintptr_t end_offset = end - chunk->address();
DCHECK_LT(start_offset, end_offset);
if (end_offset < static_cast<uintptr_t>(Page::kPageSize)) {
slot_set->RemoveRange(static_cast<int>(start_offset),
static_cast<int>(end_offset), mode);
} else {
// The large page has multiple slot sets.
// Compute slot set indicies for the range [start_offset, end_offset).
int start_chunk = static_cast<int>(start_offset / Page::kPageSize);
int end_chunk = static_cast<int>((end_offset - 1) / Page::kPageSize);
int offset_in_start_chunk =
static_cast<int>(start_offset % Page::kPageSize);
// Note that using end_offset % Page::kPageSize would be incorrect
// because end_offset is one beyond the last slot to clear.
int offset_in_end_chunk = static_cast<int>(
end_offset - static_cast<uintptr_t>(end_chunk) * Page::kPageSize);
if (start_chunk == end_chunk) {
slot_set[start_chunk].RemoveRange(offset_in_start_chunk,
offset_in_end_chunk, mode);
} else {
// Clear all slots from start_offset to the end of first chunk.
slot_set[start_chunk].RemoveRange(offset_in_start_chunk,
Page::kPageSize, mode);
// Clear all slots in intermediate chunks.
for (int i = start_chunk + 1; i < end_chunk; i++) {
slot_set[i].RemoveRange(0, Page::kPageSize, mode);
}
// Clear slots from the beginning of the last page to end_offset.
slot_set[end_chunk].RemoveRange(0, offset_in_end_chunk, mode);
}
}
}
}
// Iterates and filters the remembered set with the given callback.
// The callback should take (Address slot) and return SlotCallbackResult.
template <typename Callback>
static void Iterate(Heap* heap, RememberedSetIterationMode mode,
Callback callback) {
IterateMemoryChunks(heap, [mode, callback](MemoryChunk* chunk) {
if (mode == SYNCHRONIZED) chunk->mutex()->Lock();
Iterate(chunk, callback);
if (mode == SYNCHRONIZED) chunk->mutex()->Unlock();
});
}
// Iterates over all memory chunks that contains non-empty slot sets.
// The callback should take (MemoryChunk* chunk) and return void.
template <typename Callback>
static void IterateMemoryChunks(Heap* heap, Callback callback) {
OldGenerationMemoryChunkIterator it(heap);
MemoryChunk* chunk;
while ((chunk = it.next()) != nullptr) {
SlotSet* slots = chunk->slot_set<type>();
TypedSlotSet* typed_slots = chunk->typed_slot_set<type>();
if (slots != nullptr || typed_slots != nullptr ||
chunk->invalidated_slots() != nullptr) {
callback(chunk);
}
}
}
// Iterates and filters the remembered set in the given memory chunk with
// the given callback. The callback should take (Address slot) and return
// SlotCallbackResult.
//
// Notice that |mode| can only be of FREE* or PREFREE* if there are no other
// threads concurrently inserting slots.
template <typename Callback>
static void Iterate(MemoryChunk* chunk, Callback callback,
SlotSet::EmptyBucketMode mode) {
SlotSet* slots = chunk->slot_set<type>();
if (slots != nullptr) {
size_t pages = (chunk->size() + Page::kPageSize - 1) / Page::kPageSize;
int new_count = 0;
for (size_t page = 0; page < pages; page++) {
new_count += slots[page].Iterate(callback, mode);
}
// Only old-to-old slot sets are released eagerly. Old-new-slot sets are
// released by the sweeper threads.
if (type == OLD_TO_OLD && new_count == 0) {
chunk->ReleaseSlotSet<OLD_TO_OLD>();
}
}
}
static int NumberOfPreFreedEmptyBuckets(MemoryChunk* chunk) {
DCHECK(type == OLD_TO_NEW);
int result = 0;
SlotSet* slots = chunk->slot_set<type>();
if (slots != nullptr) {
size_t pages = (chunk->size() + Page::kPageSize - 1) / Page::kPageSize;
for (size_t page = 0; page < pages; page++) {
result += slots[page].NumberOfPreFreedEmptyBuckets();
}
}
return result;
}
static void PreFreeEmptyBuckets(MemoryChunk* chunk) {
DCHECK(type == OLD_TO_NEW);
SlotSet* slots = chunk->slot_set<type>();
if (slots != nullptr) {
size_t pages = (chunk->size() + Page::kPageSize - 1) / Page::kPageSize;
for (size_t page = 0; page < pages; page++) {
slots[page].PreFreeEmptyBuckets();
}
}
}
static void FreeEmptyBuckets(MemoryChunk* chunk) {
DCHECK(type == OLD_TO_NEW);
SlotSet* slots = chunk->slot_set<type>();
if (slots != nullptr) {
size_t pages = (chunk->size() + Page::kPageSize - 1) / Page::kPageSize;
for (size_t page = 0; page < pages; page++) {
slots[page].FreeEmptyBuckets();
slots[page].FreeToBeFreedBuckets();
}
}
}
// Given a page and a typed slot in that page, this function adds the slot
// to the remembered set.
static void InsertTyped(MemoryChunk* memory_chunk, SlotType slot_type,
uint32_t offset) {
TypedSlotSet* slot_set = memory_chunk->typed_slot_set<type>();
if (slot_set == nullptr) {
slot_set = memory_chunk->AllocateTypedSlotSet<type>();
}
slot_set->Insert(slot_type, offset);
}
static void MergeTyped(MemoryChunk* page, std::unique_ptr<TypedSlots> slots) {
TypedSlotSet* slot_set = page->typed_slot_set<type>();
if (slot_set == nullptr) {
slot_set = page->AllocateTypedSlotSet<type>();
}
slot_set->Merge(slots.get());
}
// Given a page and a range of typed slots in that page, this function removes
// the slots from the remembered set.
static void RemoveRangeTyped(MemoryChunk* page, Address start, Address end) {
TypedSlotSet* slots = page->typed_slot_set<type>();
if (slots != nullptr) {
slots->Iterate(
[=](SlotType slot_type, Address slot_addr) {
return start <= slot_addr && slot_addr < end ? REMOVE_SLOT
: KEEP_SLOT;
},
TypedSlotSet::PREFREE_EMPTY_CHUNKS);
}
}
// Iterates and filters the remembered set with the given callback.
// The callback should take (SlotType slot_type, Address addr) and return
// SlotCallbackResult.
template <typename Callback>
static void IterateTyped(Heap* heap, RememberedSetIterationMode mode,
Callback callback) {
IterateMemoryChunks(heap, [mode, callback](MemoryChunk* chunk) {
if (mode == SYNCHRONIZED) chunk->mutex()->Lock();
IterateTyped(chunk, callback);
if (mode == SYNCHRONIZED) chunk->mutex()->Unlock();
});
}
// Iterates and filters typed old to old pointers in the given memory chunk
// with the given callback. The callback should take (SlotType slot_type,
// Address addr) and return SlotCallbackResult.
template <typename Callback>
static void IterateTyped(MemoryChunk* chunk, Callback callback) {
TypedSlotSet* slots = chunk->typed_slot_set<type>();
if (slots != nullptr) {
int new_count = slots->Iterate(callback, TypedSlotSet::KEEP_EMPTY_CHUNKS);
if (new_count == 0) {
chunk->ReleaseTypedSlotSet<type>();
}
}
}
// Clear all old to old slots from the remembered set.
static void ClearAll(Heap* heap) {
STATIC_ASSERT(type == OLD_TO_OLD);
OldGenerationMemoryChunkIterator it(heap);
MemoryChunk* chunk;
while ((chunk = it.next()) != nullptr) {
chunk->ReleaseSlotSet<OLD_TO_OLD>();
chunk->ReleaseTypedSlotSet<OLD_TO_OLD>();
chunk->ReleaseInvalidatedSlots();
}
}
private:
static bool IsValidSlot(Heap* heap, MemoryChunk* chunk, ObjectSlot slot);
};
class UpdateTypedSlotHelper {
public:
// Updates a typed slot using an untyped slot callback where |addr| depending
// on slot type represents either address for respective RelocInfo or address
// of the uncompressed constant pool entry.
// The callback accepts FullMaybeObjectSlot and returns SlotCallbackResult.
template <typename Callback>
static SlotCallbackResult UpdateTypedSlot(Heap* heap, SlotType slot_type,
Address addr, Callback callback) {
switch (slot_type) {
case CODE_TARGET_SLOT: {
RelocInfo rinfo(addr, RelocInfo::CODE_TARGET, 0, Code());
return UpdateCodeTarget(&rinfo, callback);
}
case CODE_ENTRY_SLOT: {
return UpdateCodeEntry(addr, callback);
}
case COMPRESSED_EMBEDDED_OBJECT_SLOT: {
RelocInfo rinfo(addr, RelocInfo::COMPRESSED_EMBEDDED_OBJECT, 0, Code());
return UpdateEmbeddedPointer(heap, &rinfo, callback);
}
case FULL_EMBEDDED_OBJECT_SLOT: {
RelocInfo rinfo(addr, RelocInfo::FULL_EMBEDDED_OBJECT, 0, Code());
return UpdateEmbeddedPointer(heap, &rinfo, callback);
}
case OBJECT_SLOT: {
return callback(FullMaybeObjectSlot(addr));
}
case CLEARED_SLOT:
break;
}
UNREACHABLE();
}
private:
// Updates a code entry slot using an untyped slot callback.
// The callback accepts FullMaybeObjectSlot and returns SlotCallbackResult.
template <typename Callback>
static SlotCallbackResult UpdateCodeEntry(Address entry_address,
Callback callback) {
Code code = Code::GetObjectFromEntryAddress(entry_address);
Code old_code = code;
SlotCallbackResult result = callback(FullMaybeObjectSlot(&code));
DCHECK(!HasWeakHeapObjectTag(code));
if (code != old_code) {
Memory<Address>(entry_address) = code.entry();
}
return result;
}
// Updates a code target slot using an untyped slot callback.
// The callback accepts FullMaybeObjectSlot and returns SlotCallbackResult.
template <typename Callback>
static SlotCallbackResult UpdateCodeTarget(RelocInfo* rinfo,
Callback callback) {
DCHECK(RelocInfo::IsCodeTargetMode(rinfo->rmode()));
Code old_target = Code::GetCodeFromTargetAddress(rinfo->target_address());
Code new_target = old_target;
SlotCallbackResult result = callback(FullMaybeObjectSlot(&new_target));
DCHECK(!HasWeakHeapObjectTag(new_target));
if (new_target != old_target) {
rinfo->set_target_address(Code::cast(new_target).raw_instruction_start());
}
return result;
}
// Updates an embedded pointer slot using an untyped slot callback.
// The callback accepts FullMaybeObjectSlot and returns SlotCallbackResult.
template <typename Callback>
static SlotCallbackResult UpdateEmbeddedPointer(Heap* heap, RelocInfo* rinfo,
Callback callback) {
DCHECK(RelocInfo::IsEmbeddedObjectMode(rinfo->rmode()));
HeapObject old_target = rinfo->target_object_no_host(heap->isolate());
HeapObject new_target = old_target;
SlotCallbackResult result = callback(FullMaybeObjectSlot(&new_target));
DCHECK(!HasWeakHeapObjectTag(new_target));
if (new_target != old_target) {
rinfo->set_target_object(heap, HeapObject::cast(new_target));
}
return result;
}
};
inline SlotType SlotTypeForRelocInfoMode(RelocInfo::Mode rmode) {
if (RelocInfo::IsCodeTargetMode(rmode)) {
return CODE_TARGET_SLOT;
} else if (RelocInfo::IsFullEmbeddedObject(rmode)) {
return FULL_EMBEDDED_OBJECT_SLOT;
} else if (RelocInfo::IsCompressedEmbeddedObject(rmode)) {
return COMPRESSED_EMBEDDED_OBJECT_SLOT;
}
UNREACHABLE();
}
} // namespace internal
} // namespace v8
#endif // V8_HEAP_REMEMBERED_SET_H_