Line data Source code
1 : // Copyright 2011 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_STORE_BUFFER_H_
6 : #define V8_HEAP_STORE_BUFFER_H_
7 :
8 : #include "src/allocation.h"
9 : #include "src/base/logging.h"
10 : #include "src/base/platform/platform.h"
11 : #include "src/cancelable-task.h"
12 : #include "src/globals.h"
13 : #include "src/heap/gc-tracer.h"
14 : #include "src/heap/remembered-set.h"
15 : #include "src/heap/slot-set.h"
16 :
17 : namespace v8 {
18 : namespace internal {
19 :
20 : // Intermediate buffer that accumulates old-to-new stores from the generated
21 : // code. Moreover, it stores invalid old-to-new slots with two entries.
22 : // The first is a tagged address of the start of the invalid range, the second
23 : // one is the end address of the invalid range or null if there is just one slot
24 : // that needs to be removed from the remembered set. On buffer overflow the
25 : // slots are moved to the remembered set.
26 : // Store buffer entries are always full pointers.
27 62868 : class StoreBuffer {
28 : public:
29 : enum StoreBufferMode { IN_GC, NOT_IN_GC };
30 :
31 : static const int kStoreBuffers = 2;
32 : static const int kStoreBufferSize =
33 : Max(static_cast<int>(kMinExpectedOSPageSize / kStoreBuffers),
34 : 1 << (11 + kSystemPointerSizeLog2));
35 : static const int kStoreBufferMask = kStoreBufferSize - 1;
36 : static const intptr_t kDeletionTag = 1;
37 :
38 : V8_EXPORT_PRIVATE static int StoreBufferOverflow(Isolate* isolate);
39 :
40 : static void DeleteDuringGarbageCollection(StoreBuffer* store_buffer,
41 : Address start, Address end);
42 : static void InsertDuringGarbageCollection(StoreBuffer* store_buffer,
43 : Address slot);
44 :
45 : static void DeleteDuringRuntime(StoreBuffer* store_buffer, Address start,
46 : Address end);
47 : static void InsertDuringRuntime(StoreBuffer* store_buffer, Address slot);
48 :
49 : explicit StoreBuffer(Heap* heap);
50 : void SetUp();
51 : void TearDown();
52 :
53 : // Used to add entries from generated code.
54 : inline Address* top_address() { return reinterpret_cast<Address*>(&top_); }
55 :
56 : // Moves entries from a specific store buffer to the remembered set. This
57 : // method takes a lock.
58 : void MoveEntriesToRememberedSet(int index);
59 :
60 : // This method ensures that all used store buffer entries are transferred to
61 : // the remembered set.
62 : void MoveAllEntriesToRememberedSet();
63 :
64 : inline bool IsDeletionAddress(Address address) const {
65 180818849 : return address & kDeletionTag;
66 : }
67 :
68 : inline Address MarkDeletionAddress(Address address) {
69 17092 : return address | kDeletionTag;
70 : }
71 :
72 : inline Address UnmarkDeletionAddress(Address address) {
73 11131 : return address & ~kDeletionTag;
74 : }
75 :
76 : inline void InsertDeletionIntoStoreBuffer(Address start, Address end);
77 : inline void InsertIntoStoreBuffer(Address slot);
78 :
79 : void InsertEntry(Address slot) {
80 : // Insertions coming from the GC are directly inserted into the remembered
81 : // set. Insertions coming from the runtime are added to the store buffer to
82 : // allow concurrent processing.
83 106743130 : insertion_callback(this, slot);
84 : }
85 :
86 : // If we only want to delete a single slot, end should be set to null which
87 : // will be written into the second field. When processing the store buffer
88 : // the more efficient Remove method will be called in this case.
89 : void DeleteEntry(Address start, Address end = kNullAddress) {
90 : // Deletions coming from the GC are directly deleted from the remembered
91 : // set. Deletions coming from the runtime are added to the store buffer
92 : // to allow concurrent processing.
93 34809 : deletion_callback(this, start, end);
94 : }
95 :
96 : void SetMode(StoreBufferMode mode);
97 :
98 : // Used by the concurrent processing thread to transfer entries from the
99 : // store buffer to the remembered set.
100 : void ConcurrentlyProcessStoreBuffer();
101 :
102 : bool Empty() {
103 : for (int i = 0; i < kStoreBuffers; i++) {
104 : if (lazy_top_[i]) {
105 : return false;
106 : }
107 : }
108 : return top_ == start_[current_];
109 : }
110 :
111 : Heap* heap() { return heap_; }
112 :
113 : private:
114 : // There are two store buffers. If one store buffer fills up, the main thread
115 : // publishes the top pointer of the store buffer that needs processing in its
116 : // global lazy_top_ field. After that it start the concurrent processing
117 : // thread. The concurrent processing thread uses the pointer in lazy_top_.
118 : // It will grab the given mutex and transfer its entries to the remembered
119 : // set. If the concurrent thread does not make progress, the main thread will
120 : // perform the work.
121 : // Important: there is an ordering constrained. The store buffer with the
122 : // older entries has to be processed first.
123 : class Task : public CancelableTask {
124 : public:
125 : Task(Isolate* isolate, StoreBuffer* store_buffer)
126 : : CancelableTask(isolate),
127 : store_buffer_(store_buffer),
128 66298 : tracer_(isolate->heap()->tracer()) {}
129 132596 : ~Task() override = default;
130 :
131 : private:
132 66268 : void RunInternal() override {
133 265072 : TRACE_BACKGROUND_GC(tracer_,
134 : GCTracer::BackgroundScope::BACKGROUND_STORE_BUFFER);
135 132536 : store_buffer_->ConcurrentlyProcessStoreBuffer();
136 66268 : }
137 : StoreBuffer* store_buffer_;
138 : GCTracer* tracer_;
139 : DISALLOW_COPY_AND_ASSIGN(Task);
140 : };
141 :
142 : StoreBufferMode mode() const { return mode_; }
143 :
144 : void FlipStoreBuffers();
145 :
146 : Heap* heap_;
147 :
148 : Address* top_;
149 :
150 : // The start and the limit of the buffer that contains store slots
151 : // added from the generated code. We have two chunks of store buffers.
152 : // Whenever one fills up, we notify a concurrent processing thread and
153 : // use the other empty one in the meantime.
154 : Address* start_[kStoreBuffers];
155 : Address* limit_[kStoreBuffers];
156 :
157 : // At most one lazy_top_ pointer is set at any time.
158 : Address* lazy_top_[kStoreBuffers];
159 : base::Mutex mutex_;
160 :
161 : // We only want to have at most one concurrent processing tas running.
162 : bool task_running_;
163 :
164 : // Points to the current buffer in use.
165 : int current_;
166 :
167 : // During GC, entries are directly added to the remembered set without
168 : // going through the store buffer. This is signaled by a special
169 : // IN_GC mode.
170 : StoreBufferMode mode_;
171 :
172 : VirtualMemory virtual_memory_;
173 :
174 : // Callbacks are more efficient than reading out the gc state for every
175 : // store buffer operation.
176 : void (*insertion_callback)(StoreBuffer*, Address);
177 : void (*deletion_callback)(StoreBuffer*, Address, Address);
178 : };
179 :
180 : } // namespace internal
181 : } // namespace v8
182 :
183 : #endif // V8_HEAP_STORE_BUFFER_H_
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