1 // Copyright 2006-2008 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 // The common functionality when building with or without snapshots.
6
7 #include "src/snapshot/snapshot.h"
8
9 #include "src/api.h"
10 #include "src/base/platform/platform.h"
11 #include "src/full-codegen/full-codegen.h"
12
13 namespace v8 {
14 namespace internal {
15
16 #ifdef DEBUG
SnapshotIsValid(v8::StartupData * snapshot_blob)17 bool Snapshot::SnapshotIsValid(v8::StartupData* snapshot_blob) {
18 return !Snapshot::ExtractStartupData(snapshot_blob).is_empty() &&
19 !Snapshot::ExtractContextData(snapshot_blob).is_empty();
20 }
21 #endif // DEBUG
22
23
HaveASnapshotToStartFrom(Isolate * isolate)24 bool Snapshot::HaveASnapshotToStartFrom(Isolate* isolate) {
25 // Do not use snapshots if the isolate is used to create snapshots.
26 return isolate->snapshot_blob() != NULL &&
27 isolate->snapshot_blob()->data != NULL;
28 }
29
30
EmbedsScript(Isolate * isolate)31 bool Snapshot::EmbedsScript(Isolate* isolate) {
32 if (!isolate->snapshot_available()) return false;
33 return ExtractMetadata(isolate->snapshot_blob()).embeds_script();
34 }
35
36
SizeOfFirstPage(Isolate * isolate,AllocationSpace space)37 uint32_t Snapshot::SizeOfFirstPage(Isolate* isolate, AllocationSpace space) {
38 DCHECK(space >= FIRST_PAGED_SPACE && space <= LAST_PAGED_SPACE);
39 if (!isolate->snapshot_available()) {
40 return static_cast<uint32_t>(MemoryAllocator::PageAreaSize(space));
41 }
42 uint32_t size;
43 int offset = kFirstPageSizesOffset + (space - FIRST_PAGED_SPACE) * kInt32Size;
44 memcpy(&size, isolate->snapshot_blob()->data + offset, kInt32Size);
45 return size;
46 }
47
48
Initialize(Isolate * isolate)49 bool Snapshot::Initialize(Isolate* isolate) {
50 if (!isolate->snapshot_available()) return false;
51 base::ElapsedTimer timer;
52 if (FLAG_profile_deserialization) timer.Start();
53
54 const v8::StartupData* blob = isolate->snapshot_blob();
55 Vector<const byte> startup_data = ExtractStartupData(blob);
56 SnapshotData snapshot_data(startup_data);
57 Deserializer deserializer(&snapshot_data);
58 bool success = isolate->Init(&deserializer);
59 if (FLAG_profile_deserialization) {
60 double ms = timer.Elapsed().InMillisecondsF();
61 int bytes = startup_data.length();
62 PrintF("[Deserializing isolate (%d bytes) took %0.3f ms]\n", bytes, ms);
63 }
64 return success;
65 }
66
67
NewContextFromSnapshot(Isolate * isolate,Handle<JSGlobalProxy> global_proxy)68 MaybeHandle<Context> Snapshot::NewContextFromSnapshot(
69 Isolate* isolate, Handle<JSGlobalProxy> global_proxy) {
70 if (!isolate->snapshot_available()) return Handle<Context>();
71 base::ElapsedTimer timer;
72 if (FLAG_profile_deserialization) timer.Start();
73
74 const v8::StartupData* blob = isolate->snapshot_blob();
75 Vector<const byte> context_data = ExtractContextData(blob);
76 SnapshotData snapshot_data(context_data);
77 Deserializer deserializer(&snapshot_data);
78
79 MaybeHandle<Object> maybe_context =
80 deserializer.DeserializePartial(isolate, global_proxy);
81 Handle<Object> result;
82 if (!maybe_context.ToHandle(&result)) return MaybeHandle<Context>();
83 CHECK(result->IsContext());
84 if (FLAG_profile_deserialization) {
85 double ms = timer.Elapsed().InMillisecondsF();
86 int bytes = context_data.length();
87 PrintF("[Deserializing context (%d bytes) took %0.3f ms]\n", bytes, ms);
88 }
89 return Handle<Context>::cast(result);
90 }
91
92
CalculateFirstPageSizes(bool is_default_snapshot,const SnapshotData & startup_snapshot,const SnapshotData & context_snapshot,uint32_t * sizes_out)93 void CalculateFirstPageSizes(bool is_default_snapshot,
94 const SnapshotData& startup_snapshot,
95 const SnapshotData& context_snapshot,
96 uint32_t* sizes_out) {
97 Vector<const SerializedData::Reservation> startup_reservations =
98 startup_snapshot.Reservations();
99 Vector<const SerializedData::Reservation> context_reservations =
100 context_snapshot.Reservations();
101 int startup_index = 0;
102 int context_index = 0;
103
104 if (FLAG_profile_deserialization) {
105 int startup_total = 0;
106 int context_total = 0;
107 for (auto& reservation : startup_reservations) {
108 startup_total += reservation.chunk_size();
109 }
110 for (auto& reservation : context_reservations) {
111 context_total += reservation.chunk_size();
112 }
113 PrintF(
114 "Deserialization will reserve:\n"
115 "%10d bytes per isolate\n"
116 "%10d bytes per context\n",
117 startup_total, context_total);
118 }
119
120 for (int space = 0; space < i::Serializer::kNumberOfSpaces; space++) {
121 bool single_chunk = true;
122 while (!startup_reservations[startup_index].is_last()) {
123 single_chunk = false;
124 startup_index++;
125 }
126 while (!context_reservations[context_index].is_last()) {
127 single_chunk = false;
128 context_index++;
129 }
130
131 uint32_t required = kMaxUInt32;
132 if (single_chunk) {
133 // If both the startup snapshot data and the context snapshot data on
134 // this space fit in a single page, then we consider limiting the size
135 // of the first page. For this, we add the chunk sizes and some extra
136 // allowance. This way we achieve a smaller startup memory footprint.
137 required = (startup_reservations[startup_index].chunk_size() +
138 2 * context_reservations[context_index].chunk_size()) +
139 Page::kObjectStartOffset;
140 // Add a small allowance to the code space for small scripts.
141 if (space == CODE_SPACE) required += 32 * KB;
142 } else {
143 // We expect the vanilla snapshot to only require on page per space.
144 DCHECK(!is_default_snapshot);
145 }
146
147 if (space >= FIRST_PAGED_SPACE && space <= LAST_PAGED_SPACE) {
148 uint32_t max_size =
149 MemoryAllocator::PageAreaSize(static_cast<AllocationSpace>(space));
150 sizes_out[space - FIRST_PAGED_SPACE] = Min(required, max_size);
151 } else {
152 DCHECK(single_chunk);
153 }
154 startup_index++;
155 context_index++;
156 }
157
158 DCHECK_EQ(startup_reservations.length(), startup_index);
159 DCHECK_EQ(context_reservations.length(), context_index);
160 }
161
162
CreateSnapshotBlob(const i::StartupSerializer & startup_ser,const i::PartialSerializer & context_ser,Snapshot::Metadata metadata)163 v8::StartupData Snapshot::CreateSnapshotBlob(
164 const i::StartupSerializer& startup_ser,
165 const i::PartialSerializer& context_ser, Snapshot::Metadata metadata) {
166 SnapshotData startup_snapshot(startup_ser);
167 SnapshotData context_snapshot(context_ser);
168 Vector<const byte> startup_data = startup_snapshot.RawData();
169 Vector<const byte> context_data = context_snapshot.RawData();
170
171 uint32_t first_page_sizes[kNumPagedSpaces];
172
173 CalculateFirstPageSizes(!metadata.embeds_script(), startup_snapshot,
174 context_snapshot, first_page_sizes);
175
176 int startup_length = startup_data.length();
177 int context_length = context_data.length();
178 int context_offset = ContextOffset(startup_length);
179
180 int length = context_offset + context_length;
181 char* data = new char[length];
182
183 memcpy(data + kMetadataOffset, &metadata.RawValue(), kInt32Size);
184 memcpy(data + kFirstPageSizesOffset, first_page_sizes,
185 kNumPagedSpaces * kInt32Size);
186 memcpy(data + kStartupLengthOffset, &startup_length, kInt32Size);
187 memcpy(data + kStartupDataOffset, startup_data.begin(), startup_length);
188 memcpy(data + context_offset, context_data.begin(), context_length);
189 v8::StartupData result = {data, length};
190
191 if (FLAG_profile_deserialization) {
192 PrintF(
193 "Snapshot blob consists of:\n"
194 "%10d bytes for startup\n"
195 "%10d bytes for context\n",
196 startup_length, context_length);
197 }
198 return result;
199 }
200
201
ExtractMetadata(const v8::StartupData * data)202 Snapshot::Metadata Snapshot::ExtractMetadata(const v8::StartupData* data) {
203 uint32_t raw;
204 memcpy(&raw, data->data + kMetadataOffset, kInt32Size);
205 return Metadata(raw);
206 }
207
208
ExtractStartupData(const v8::StartupData * data)209 Vector<const byte> Snapshot::ExtractStartupData(const v8::StartupData* data) {
210 DCHECK_LT(kIntSize, data->raw_size);
211 int startup_length;
212 memcpy(&startup_length, data->data + kStartupLengthOffset, kInt32Size);
213 DCHECK_LT(startup_length, data->raw_size);
214 const byte* startup_data =
215 reinterpret_cast<const byte*>(data->data + kStartupDataOffset);
216 return Vector<const byte>(startup_data, startup_length);
217 }
218
219
ExtractContextData(const v8::StartupData * data)220 Vector<const byte> Snapshot::ExtractContextData(const v8::StartupData* data) {
221 DCHECK_LT(kIntSize, data->raw_size);
222 int startup_length;
223 memcpy(&startup_length, data->data + kStartupLengthOffset, kIntSize);
224 int context_offset = ContextOffset(startup_length);
225 const byte* context_data =
226 reinterpret_cast<const byte*>(data->data + context_offset);
227 DCHECK_LT(context_offset, data->raw_size);
228 int context_length = data->raw_size - context_offset;
229 return Vector<const byte>(context_data, context_length);
230 }
231 } // namespace internal
232 } // namespace v8
233