Limit size of first page based on serialized data.

src/snapshot-common.cc

 // Copyright 2006-2008 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.
 
 // The common functionality when building with or without snapshots.
 
 #include "src/v8.h"
 
 #include "src/api.h"
 #include "src/base/platform/platform.h"
-#include "src/serialize.h"
+#include "src/full-codegen.h"
 #include "src/snapshot.h"
 
 namespace v8 {
 namespace internal {
 
 bool Snapshot::HaveASnapshotToStartFrom() {
   return SnapshotBlob().data != NULL;
 }
 
 
 #ifdef DEBUG
 bool Snapshot::SnapshotIsValid(v8::StartupData* snapshot_blob) {
   return !Snapshot::ExtractStartupData(snapshot_blob).is_empty() &&
          !Snapshot::ExtractContextData(snapshot_blob).is_empty();
 }
 #endif  // DEBUG
 
 
 bool Snapshot::EmbedsScript() {
   if (!HaveASnapshotToStartFrom()) return false;
   const v8::StartupData blob = SnapshotBlob();
   return ExtractMetadata(&blob).embeds_script();
 }
 
 
+uint32_t Snapshot::SizeOfFirstPage(AllocationSpace space) {
+  DCHECK(space >= FIRST_PAGED_SPACE && space <= LAST_PAGED_SPACE);
+  if (!HaveASnapshotToStartFrom()) {
+    return static_cast<uint32_t>(MemoryAllocator::PageAreaSize(space));
+  }
+  uint32_t size;
+  int offset = kFirstPageSizesOffset + (space - FIRST_PAGED_SPACE) * kInt32Size;
+  memcpy(&size, SnapshotBlob().data + offset, kInt32Size);
+  return size;
+}
+
+
 bool Snapshot::Initialize(Isolate* isolate) {
   if (!HaveASnapshotToStartFrom()) return false;
   base::ElapsedTimer timer;
   if (FLAG_profile_deserialization) timer.Start();
 
   const v8::StartupData blob = SnapshotBlob();
   Vector<const byte> startup_data = ExtractStartupData(&blob);
   SnapshotData snapshot_data(startup_data);
   Deserializer deserializer(&snapshot_data);
   bool success = isolate->Init(&deserializer);
@@ skipping 28 matching lines @@
   CHECK(EmbedsScript() || (*outdated_contexts_out)->length() == 1);
   if (FLAG_profile_deserialization) {
     double ms = timer.Elapsed().InMillisecondsF();
     int bytes = context_data.length();
     PrintF("[Deserializing context (%d bytes) took %0.3f ms]\n", bytes, ms);
   }
   return Handle<Context>::cast(result);
 }
 
 
+void CalculateFirstPageSizes(bool is_default_snapshot,
+                             const SnapshotData& startup_snapshot,
+                             const SnapshotData& context_snapshot,
+                             uint32_t* sizes_out) {
+  Vector<const SerializedData::Reservation> startup_reservations =
+      startup_snapshot.Reservations();
+  Vector<const SerializedData::Reservation> context_reservations =
+      context_snapshot.Reservations();
+  int startup_index = 0;
+  int context_index = 0;
+  for (int space = 0; space < i::Serializer::kNumberOfSpaces; space++) {
+    bool single_chunk = true;
+    while (!startup_reservations[startup_index].is_last()) {
+      single_chunk = false;
+      startup_index++;
+    }
+    while (!context_reservations[context_index].is_last()) {
+      single_chunk = false;
+      context_index++;
+    }
+
+    uint32_t required = kMaxUInt32;
+    if (single_chunk) {
+      // If both the startup snapshot data and the context snapshot data on
+      // this space fit in a single page, then we consider limiting the size
+      // of the first page. For this, we add the chunk sizes and an additional
+      // 25% allowance. This way we achieve a smaller startup memory footprint.
+      required = (startup_reservations[startup_index].chunk_size() +
+                  context_reservations[context_index].chunk_size()) /
+                     4 * 5 +
+                 Page::kObjectStartOffset;
+    } else {
+      // We expect the vanilla snapshot to only require on page per space.
+      DCHECK(!is_default_snapshot);
+    }
+
+    if (space >= FIRST_PAGED_SPACE && space <= LAST_PAGED_SPACE) {
+      uint32_t max_size =
+          MemoryAllocator::PageAreaSize(static_cast<AllocationSpace>(space));
+      sizes_out[space - FIRST_PAGED_SPACE] = Min(required, max_size);
+    } else {
+      DCHECK(single_chunk);
+    }
+    startup_index++;
+    context_index++;
+  }
+
+  DCHECK_EQ(startup_reservations.length(), startup_index);
+  DCHECK_EQ(context_reservations.length(), context_index);
+}
+
+
 v8::StartupData Snapshot::CreateSnapshotBlob(
-    const Vector<const byte> startup_data,
-    const Vector<const byte> context_data, Snapshot::Metadata metadata) {
+    const i::StartupSerializer& startup_ser,
+    const i::PartialSerializer& context_ser, Snapshot::Metadata metadata) {
+  SnapshotData startup_snapshot(startup_ser);
+  SnapshotData context_snapshot(context_ser);
+  Vector<const byte> startup_data = startup_snapshot.RawData();
+  Vector<const byte> context_data = context_snapshot.RawData();
+
+  uint32_t first_page_sizes[kNumPagedSpaces];
+
+  CalculateFirstPageSizes(metadata.embeds_script(), startup_snapshot,
+                          context_snapshot, first_page_sizes);
+
   int startup_length = startup_data.length();
   int context_length = context_data.length();
   int context_offset = ContextOffset(startup_length);
 
   int length = context_offset + context_length;
   char* data = new char[length];
 
   memcpy(data + kMetadataOffset, &metadata.RawValue(), kInt32Size);
+  memcpy(data + kFirstPageSizesOffset, first_page_sizes,
+         kNumPagedSpaces * kInt32Size);
   memcpy(data + kStartupLengthOffset, &startup_length, kInt32Size);
   memcpy(data + kStartupDataOffset, startup_data.begin(), startup_length);
   memcpy(data + context_offset, context_data.begin(), context_length);
   v8::StartupData result = {data, length};
   return result;
 }
 
 
 Snapshot::Metadata Snapshot::ExtractMetadata(const v8::StartupData* data) {
   uint32_t raw;
@@ skipping 18 matching lines @@
   int startup_length;
   memcpy(&startup_length, data->data + kStartupLengthOffset, kIntSize);
   int context_offset = ContextOffset(startup_length);
   const byte* context_data =
       reinterpret_cast<const byte*>(data->data + context_offset);
   DCHECK_LT(context_offset, data->raw_size);
   int context_length = data->raw_size - context_offset;
   return Vector<const byte>(context_data, context_length);
 }
 } }  // namespace v8::internal