Speedup the snapshot serialization.

src/profile-generator.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1065 matching lines @@
         OS::Print("\\n");
       ++c;
     }
     OS::Print("\"\n");
   }
   if (--max_depth == 0) return;
   Vector<HeapGraphEdge> ch = children();
   for (int i = 0; i < ch.length(); ++i) {
     HeapGraphEdge& edge = ch[i];
     const char* edge_prefix = "";
-    ScopedVector<char> index(64);
+    EmbeddedVector<char, 64> index;
     const char* edge_name = index.start();
     switch (edge.type()) {
       case HeapGraphEdge::kContextVariable:
         edge_prefix = "#";
         edge_name = edge.name();
         break;
       case HeapGraphEdge::kElement:
         OS::SNPrintF(index, "%d", edge.index());
         break;
       case HeapGraphEdge::kInternal:
@@ skipping 60 matching lines @@
   void Apply(HeapEntry** entry_ptr) {
     if ((*entry_ptr)->painted_reachable()) {
       retained_size_ += (*entry_ptr)->self_size();
     }
   }
 
  private:
   int retained_size_;
 };
 
+
 void HeapEntry::CalculateExactRetainedSize() {
   // To calculate retained size, first we paint all reachable nodes in
   // one color, then we paint (or re-paint) all nodes reachable from
   // other nodes with a different color. Then we sum up self sizes of
   // nodes painted with the first color.
   snapshot()->ClearPaint();
   PaintAllReachable();
 
   List<HeapEntry*> list(10);
   HeapEntry* root = snapshot()->root();
@@ skipping 59 matching lines @@
       sizeof(HeapGraphEdge) ==
       SnapshotSizeConstants<kPointerSize>::kExpectedHeapGraphEdgeSize);
   STATIC_ASSERT(
       sizeof(HeapEntry) ==
       SnapshotSizeConstants<kPointerSize>::kExpectedHeapEntrySize);
   for (int i = 0; i < VisitorSynchronization::kNumberOfSyncTags; ++i) {
     gc_subroot_entries_[i] = NULL;
   }
 }
 
+
 HeapSnapshot::~HeapSnapshot() {
   DeleteArray(raw_entries_);
 }
 
 
 void HeapSnapshot::Delete() {
   collection_->RemoveSnapshot(this);
   delete this;
 }
 
 
 void HeapSnapshot::AllocateEntries(int entries_count,
                                    int children_count,
                                    int retainers_count) {
   ASSERT(raw_entries_ == NULL);
   raw_entries_size_ =
       HeapEntry::EntriesSize(entries_count, children_count, retainers_count);
   raw_entries_ = NewArray<char>(raw_entries_size_);
 }
 
 
 static void HeapEntryClearPaint(HeapEntry** entry_ptr) {
   (*entry_ptr)->clear_paint();
 }
 
+
 void HeapSnapshot::ClearPaint() {
   entries_.Iterate(HeapEntryClearPaint);
 }
 
 
 HeapEntry* HeapSnapshot::AddRootEntry(int children_count) {
   ASSERT(root_entry_ == NULL);
   return (root_entry_ = AddEntry(HeapEntry::kObject,
                                  "",
                                  HeapObjectsMap::kInternalRootObjectId,
@@ skipping 85 matching lines @@
 }
 
 
 template<class T>
 static int SortByIds(const T* entry1_ptr,
                      const T* entry2_ptr) {
   if ((*entry1_ptr)->id() == (*entry2_ptr)->id()) return 0;
   return (*entry1_ptr)->id() < (*entry2_ptr)->id() ? -1 : 1;
 }
 
+
 List<HeapEntry*>* HeapSnapshot::GetSortedEntriesList() {
   if (!entries_sorted_) {
     entries_.Sort(SortByIds);
     entries_sorted_ = true;
   }
   return &entries_;
 }
 
 
 void HeapSnapshot::Print(int max_depth) {
@@ skipping 1970 matching lines @@
          dominator != entry;
          entry = dominator, dominator = entry->dominator()) {
       dominator->add_retained_size(entry_size);
     }
     if (!ProgressReport()) return false;
   }
   return true;
 }
 
 
+template<int bytes> struct MaxDecimalDigitsIn;
+template<> struct MaxDecimalDigitsIn<4> {
+  static const int kSigned = 11;
+  static const int kUnsigned = 10;
+};
+template<> struct MaxDecimalDigitsIn<8> {
+  static const int kSigned = 20;
+  static const int kUnsigned = 20;
+};
+
+
 class OutputStreamWriter {
  public:
   explicit OutputStreamWriter(v8::OutputStream* stream)
       : stream_(stream),
         chunk_size_(stream->GetChunkSize()),
         chunk_(chunk_size_),
         chunk_pos_(0),
         aborted_(false) {
     ASSERT(chunk_size_ > 0);
   }
@@ skipping 29 matching lines @@
     ASSERT(chunk_pos_ < chunk_size_);
     if (chunk_pos_ != 0) {
       WriteChunk();
     }
     stream_->EndOfStream();
   }
 
  private:
   template<typename T>
   void AddNumberImpl(T n, const char* format) {
-    ScopedVector<char> buffer(32);
-    int result = OS::SNPrintF(buffer, format, n);
-    USE(result);
-    ASSERT(result != -1);
-    AddString(buffer.start());
+    // Buffer for long long value plus trailing \0
+    static const int kMaxNumberSize =
+        MaxDecimalDigitsIn<sizeof(long long)>::kUnsigned + 1;  // NOLINT

[mnaganov (inactive), 2012/02/21 14:21:54]

I will change "long long" to "T" (and update the comment), because "long long"
isn't the part of ISO 1998 C++ standard and hence doesn't compile in a
standalone V8.

If you are OK with this, I'll submit your change.

+    if (chunk_size_ - chunk_pos_ >= kMaxNumberSize) {
+      int result = OS::SNPrintF(
+          chunk_.SubVector(chunk_pos_, chunk_size_), format, n);
+      ASSERT(result != -1);
+      chunk_pos_ += result;
+      MaybeWriteChunk();
+    } else {
+      EmbeddedVector<char, kMaxNumberSize> buffer;
+      int result = OS::SNPrintF(buffer, format, n);
+      USE(result);
+      ASSERT(result != -1);
+      AddString(buffer.start());
+    }
   }
   void MaybeWriteChunk() {
     ASSERT(chunk_pos_ <= chunk_size_);
     if (chunk_pos_ == chunk_size_) {
       WriteChunk();
-      chunk_pos_ = 0;
     }
   }
   void WriteChunk() {
     if (aborted_) return;
     if (stream_->WriteAsciiChunk(chunk_.start(), chunk_pos_) ==
         v8::OutputStream::kAbort) aborted_ = true;
+    chunk_pos_ = 0;
   }
 
   v8::OutputStream* stream_;
   int chunk_size_;
   ScopedVector<char> chunk_;
   int chunk_pos_;
   bool aborted_;
 };
 
+
 void HeapSnapshotJSONSerializer::Serialize(v8::OutputStream* stream) {
   ASSERT(writer_ == NULL);
   writer_ = new OutputStreamWriter(stream);
 
   HeapSnapshot* original_snapshot = NULL;
   if (snapshot_->raw_entries_size() >=
       SnapshotSizeConstants<kPointerSize>::kMaxSerializableSnapshotRawSize) {
     // The snapshot is too big. Serialize a fake snapshot.
     original_snapshot = snapshot_;
     snapshot_ = CreateFakeSnapshot();
@@ skipping 85 matching lines @@
   HashMap::Entry* cache_entry = strings_.Lookup(
       const_cast<char*>(s), ObjectHash(s), true);
   if (cache_entry->value == NULL) {
     cache_entry->value = reinterpret_cast<void*>(next_string_id_++);
   }
   return static_cast<int>(reinterpret_cast<intptr_t>(cache_entry->value));
 }
 
 
 void HeapSnapshotJSONSerializer::SerializeEdge(HeapGraphEdge* edge) {
-  writer_->AddCharacter(',');
-  writer_->AddNumber(edge->type());
-  writer_->AddCharacter(',');
-  if (edge->type() == HeapGraphEdge::kElement
+  // The buffer needs space for 3 ints, 3 commas and \0
+  static const int kBufferSize =
+      MaxDecimalDigitsIn<sizeof(int)>::kSigned * 3 + 3 + 1;  // NOLINT
+  EmbeddedVector<char, kBufferSize> buffer;
+  int edge_name_or_index = edge->type() == HeapGraphEdge::kElement
       || edge->type() == HeapGraphEdge::kHidden
-      || edge->type() == HeapGraphEdge::kWeak) {
-    writer_->AddNumber(edge->index());
-  } else {
-    writer_->AddNumber(GetStringId(edge->name()));
-  }
-  writer_->AddCharacter(',');
-  writer_->AddNumber(GetNodeId(edge->to()));
+      || edge->type() == HeapGraphEdge::kWeak
+      ? edge->index() : GetStringId(edge->name());
+  int result = OS::SNPrintF(buffer, ",%d,%d,%d",
+      edge->type(), edge_name_or_index, GetNodeId(edge->to()));
+  USE(result);
+  ASSERT(result != -1);
+  writer_->AddString(buffer.start());
 }
 
 
 void HeapSnapshotJSONSerializer::SerializeNode(HeapEntry* entry) {
-  writer_->AddCharacter('\n');
-  writer_->AddCharacter(',');
-  writer_->AddNumber(entry->type());
-  writer_->AddCharacter(',');
-  writer_->AddNumber(GetStringId(entry->name()));
-  writer_->AddCharacter(',');
-  writer_->AddNumber(entry->id());
-  writer_->AddCharacter(',');
-  writer_->AddNumber(entry->self_size());
-  writer_->AddCharacter(',');
-  writer_->AddNumber(entry->RetainedSize(false));
-  writer_->AddCharacter(',');
-  writer_->AddNumber(GetNodeId(entry->dominator()));
+  // The buffer needs space for 7 ints, 7 commas, \n and \0
+  static const int kBufferSize =
+      MaxDecimalDigitsIn<sizeof(int)>::kSigned * 7 + 7 + 1 + 1;  // NOLINT
+  EmbeddedVector<char, kBufferSize> buffer;
   Vector<HeapGraphEdge> children = entry->children();
-  writer_->AddCharacter(',');
-  writer_->AddNumber(children.length());
+  int result = OS::SNPrintF(buffer, "\n,%d,%d,%d,%d,%d,%d,%d",
+      entry->type(),
+      GetStringId(entry->name()),
+      entry->id(),
+      entry->self_size(),
+      entry->RetainedSize(false),
+      GetNodeId(entry->dominator()),
+      children.length());
+  USE(result);
+  ASSERT(result != -1);
+  writer_->AddString(buffer.start());
   for (int i = 0; i < children.length(); ++i) {
     SerializeEdge(&children[i]);
     if (writer_->aborted()) return;
   }
 }
 
 
 void HeapSnapshotJSONSerializer::SerializeNodes() {
   // The first (zero) item of nodes array is an object describing node
   // serialization layout.  We use a set of macros to improve
@@ skipping 170 matching lines @@
 
 
 void HeapSnapshotJSONSerializer::SortHashMap(
     HashMap* map, List<HashMap::Entry*>* sorted_entries) {
   for (HashMap::Entry* p = map->Start(); p != NULL; p = map->Next(p))
     sorted_entries->Add(p);
   sorted_entries->Sort(SortUsingEntryValue);
 }
 
 } }  // namespace v8::internal