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Side by Side Diff: src/heap/slots-buffer.h

Issue 1735523002: Reland "Replace slots buffer with remembered set. (patchset #14 id:250001 of https://codereview.chr… (Closed) Base URL: https://chromium.googlesource.com/v8/v8.git@master
Patch Set: one more int->size_t Created 4 years, 10 months ago
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1 // Copyright 2015 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_SLOTS_BUFFER_H_
6 #define V8_HEAP_SLOTS_BUFFER_H_
7
8 #include "src/objects.h"
9
10 namespace v8 {
11 namespace internal {
12
13 // Forward declarations.
14 class SlotsBuffer;
15
16
17 // SlotsBufferAllocator manages the allocation and deallocation of slots buffer
18 // chunks and links them together. Slots buffer chunks are always created by the
19 // SlotsBufferAllocator.
20 class SlotsBufferAllocator {
21 public:
22 SlotsBuffer* AllocateBuffer(SlotsBuffer* next_buffer);
23 void DeallocateBuffer(SlotsBuffer* buffer);
24
25 void DeallocateChain(SlotsBuffer** buffer_address);
26 };
27
28
29 // SlotsBuffer records a sequence of slots that has to be updated
30 // after live objects were relocated from evacuation candidates.
31 // All slots are either untyped or typed:
32 // - Untyped slots are expected to contain a tagged object pointer.
33 // They are recorded by an address.
34 // - Typed slots are expected to contain an encoded pointer to a heap
35 // object where the way of encoding depends on the type of the slot.
36 // They are recorded as a pair (SlotType, slot address).
37 // We assume that zero-page is never mapped this allows us to distinguish
38 // untyped slots from typed slots during iteration by a simple comparison:
39 // if element of slots buffer is less than NUMBER_OF_SLOT_TYPES then it
40 // is the first element of typed slot's pair.
41 class SlotsBuffer {
42 public:
43 typedef Object** ObjectSlot;
44
45 explicit SlotsBuffer(SlotsBuffer* next_buffer)
46 : idx_(0), chain_length_(1), next_(next_buffer) {
47 if (next_ != NULL) {
48 chain_length_ = next_->chain_length_ + 1;
49 }
50 }
51
52 ~SlotsBuffer() {}
53
54 void Add(ObjectSlot slot) {
55 DCHECK(0 <= idx_ && idx_ < kNumberOfElements);
56 #ifdef DEBUG
57 if (slot >= reinterpret_cast<ObjectSlot>(NUMBER_OF_SLOT_TYPES)) {
58 DCHECK_NOT_NULL(*slot);
59 }
60 #endif
61 slots_[idx_++] = slot;
62 }
63
64 ObjectSlot Get(intptr_t i) {
65 DCHECK(i >= 0 && i < kNumberOfElements);
66 return slots_[i];
67 }
68
69 size_t Size() {
70 DCHECK(idx_ <= kNumberOfElements);
71 return idx_;
72 }
73
74 enum SlotType {
75 EMBEDDED_OBJECT_SLOT,
76 OBJECT_SLOT,
77 RELOCATED_CODE_OBJECT,
78 CELL_TARGET_SLOT,
79 CODE_TARGET_SLOT,
80 CODE_ENTRY_SLOT,
81 DEBUG_TARGET_SLOT,
82 NUMBER_OF_SLOT_TYPES
83 };
84
85 static const char* SlotTypeToString(SlotType type) {
86 switch (type) {
87 case EMBEDDED_OBJECT_SLOT:
88 return "EMBEDDED_OBJECT_SLOT";
89 case OBJECT_SLOT:
90 return "OBJECT_SLOT";
91 case RELOCATED_CODE_OBJECT:
92 return "RELOCATED_CODE_OBJECT";
93 case CELL_TARGET_SLOT:
94 return "CELL_TARGET_SLOT";
95 case CODE_TARGET_SLOT:
96 return "CODE_TARGET_SLOT";
97 case CODE_ENTRY_SLOT:
98 return "CODE_ENTRY_SLOT";
99 case DEBUG_TARGET_SLOT:
100 return "DEBUG_TARGET_SLOT";
101 case NUMBER_OF_SLOT_TYPES:
102 return "NUMBER_OF_SLOT_TYPES";
103 }
104 return "UNKNOWN SlotType";
105 }
106
107 SlotsBuffer* next() { return next_; }
108
109 static int SizeOfChain(SlotsBuffer* buffer) {
110 if (buffer == NULL) return 0;
111 return static_cast<int>(buffer->idx_ +
112 (buffer->chain_length_ - 1) * kNumberOfElements);
113 }
114
115 inline bool IsFull() { return idx_ == kNumberOfElements; }
116
117 inline bool HasSpaceForTypedSlot() { return idx_ < kNumberOfElements - 1; }
118
119 enum AdditionMode { FAIL_ON_OVERFLOW, IGNORE_OVERFLOW };
120
121 static bool ChainLengthThresholdReached(SlotsBuffer* buffer) {
122 return buffer != NULL && buffer->chain_length_ >= kChainLengthThreshold;
123 }
124
125 INLINE(static bool AddTo(SlotsBufferAllocator* allocator,
126 SlotsBuffer** buffer_address, ObjectSlot slot,
127 AdditionMode mode)) {
128 SlotsBuffer* buffer = *buffer_address;
129 if (buffer == NULL || buffer->IsFull()) {
130 if (mode == FAIL_ON_OVERFLOW && ChainLengthThresholdReached(buffer)) {
131 allocator->DeallocateChain(buffer_address);
132 return false;
133 }
134 buffer = allocator->AllocateBuffer(buffer);
135 *buffer_address = buffer;
136 }
137 buffer->Add(slot);
138 return true;
139 }
140
141 static bool IsTypedSlot(ObjectSlot slot);
142
143 static bool AddTo(SlotsBufferAllocator* allocator,
144 SlotsBuffer** buffer_address, SlotType type, Address addr,
145 AdditionMode mode);
146
147 // Eliminates all stale entries from the slots buffer, i.e., slots that
148 // are not part of live objects anymore. This method must be called after
149 // marking, when the whole transitive closure is known and must be called
150 // before sweeping when mark bits are still intact.
151 static void RemoveInvalidSlots(Heap* heap, SlotsBuffer* buffer);
152
153 // Eliminate all slots that are within the given address range.
154 static void RemoveObjectSlots(Heap* heap, SlotsBuffer* buffer,
155 Address start_slot, Address end_slot);
156
157 // Ensures that there are no invalid slots in the chain of slots buffers.
158 static void VerifySlots(Heap* heap, SlotsBuffer* buffer);
159
160 static const int kNumberOfElements = 1021;
161
162 private:
163 static const int kChainLengthThreshold = 15;
164
165 intptr_t idx_;
166 intptr_t chain_length_;
167 SlotsBuffer* next_;
168 ObjectSlot slots_[kNumberOfElements];
169 };
170
171
172 } // namespace internal
173 } // namespace v8
174
175 #endif // V8_HEAP_SLOTS_BUFFER_H_
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