Introduce a way to grab heap stats.

src/profile-generator.cc

Index: src/profile-generator.cc
diff --git a/src/profile-generator.cc b/src/profile-generator.cc
index 814ff8d68dd935c43ea8a49725f4caa63bdb82e6..979d64ebb5e82dfb6751c2fd793b6561bc8537c7 100644
--- a/src/profile-generator.cc
+++ b/src/profile-generator.cc
@@ -1406,6 +1406,84 @@ SnapshotObjectId HeapObjectsMap::FindEntry(Address addr) {
 }
 
 
+SnapshotObjectId HeapObjectsMap::FindOrAddEntry(Address addr) {
+  ASSERT(static_cast<uint32_t>(entries_->length()) > entries_map_.occupancy());
+  HashMap::Entry* entry = entries_map_.Lookup(addr, AddressHash(addr), true);
+  if (entry->value != NULL) {
+    int entry_index =
+        static_cast<int>(reinterpret_cast<intptr_t>(entry->value));
+    EntryInfo& entry_info = entries_->at(entry_index);
+    entry_info.accessed = true;
+    return entry_info.id;
+  }
+  entry->value = reinterpret_cast<void*>(entries_->length());
+  SnapshotObjectId id = next_id_;
+  next_id_ += kObjectIdStep;
+  entries_->Add(EntryInfo(id, addr));
+  ASSERT(static_cast<uint32_t>(entries_->length()) > entries_map_.occupancy());
+  return id;
+}
+
+
+void HeapObjectsMap::StopHeapObjectsTracking() {
+  fragment_infos_.Clear();
+}
+
+void HeapObjectsMap::UpdateHeapObjectsMap() {
+  HEAP->CollectAllGarbage(Heap::kMakeHeapIterableMask,
+                          "HeapSnapshotsCollection::UpdateHeapObjectsMap");
+  int entries = 0;
+  HeapIterator iterator(HeapIterator::kFilterUnreachable);
+  for (HeapObject* obj = iterator.next();
+       obj != NULL;
+       obj = iterator.next()) {
+    FindOrAddEntry(obj->address());
+    ++entries;
+  }
+  initial_fill_mode_ = false;
+  RemoveDeadEntries();
+}
+
+
+void HeapObjectsMap::PushHeapObjectsStats(OutputStream* stream) {
+  UpdateHeapObjectsMap();
+  fragment_infos_.Add(FragmentInfo(next_id_));
+  int collected_fragment_updates = 0;
+  int prefered_chunk_size = stream->GetChunkSize();
+  List<uint32_t> stats_buffer;
+  ASSERT(entries_->length());
+  EntryInfo* entry_info = &entries_->first();
+  EntryInfo* end_entry_info = &entries_->last() + 1;
+  uint32_t count = 0;
+  for (int fragment_index = 0;
+       fragment_index < fragment_infos_.length();
+       ++fragment_index) {
+    FragmentInfo& fragment_info = fragment_infos_[fragment_index];
+    SnapshotObjectId fragment_id = fragment_info.id;
+    while (entry_info < end_entry_info && entry_info->id < fragment_id) {

[alexeif, 2012/04/11 14:38:51]

it doesn't look very efficient.
May be do the binary search or better make entry info know its fragment index
and update counters when its created/deleted. wdyt?

+      ++count;
+      ++entry_info;
+    }
+    if (fragment_info.count != count) {
+      stats_buffer.Add(fragment_index);
+      stats_buffer.Add(fragment_info.count = count);
+      ++collected_fragment_updates;
+      if (stats_buffer.length() >= prefered_chunk_size) {
+        stream->WriteUint32Chunk(&stats_buffer.first(),
+                                 stats_buffer.length());
+        stats_buffer.Clear();
+      }
+    }
+    count = 0;
+  }
+  ASSERT(entry_info == end_entry_info);
+  if (stats_buffer.length()) {
+    stream->WriteUint32Chunk(&stats_buffer.first(), stats_buffer.length());
+  }
+  stream->EndOfStream();
+}
+
+
 void HeapObjectsMap::RemoveDeadEntries() {
   ASSERT(entries_->length() > 0 &&
          entries_->at(0).id == 0 &&