Heap Snapshot maximum size limit is too low for really big apps.

src/profile-generator.cc

Index: src/profile-generator.cc
diff --git a/src/profile-generator.cc b/src/profile-generator.cc
index c6e6131a71ea0e343a53dc133f99e21195d9d8e0..2b5580b352abd92477943dc08c096853eaebea7b 100644
--- a/src/profile-generator.cc
+++ b/src/profile-generator.cc
@@ -3411,8 +3411,13 @@ class OutputStreamWriter {
   bool aborted_;
 };
 
+#if defined(V8_TARGET_ARCH_X64)
+const int HeapSnapshotJSONSerializer::kMaxSerializableSnapshotRawSize =
+    768 * MB;

[mnaganov (inactive), 2012/02/10 12:33:50]

I know a better place for this: SnapshotSizeConstants

+#else
 const int HeapSnapshotJSONSerializer::kMaxSerializableSnapshotRawSize =
     256 * MB;
+#endif
 
 void HeapSnapshotJSONSerializer::Serialize(v8::OutputStream* stream) {
   ASSERT(writer_ == NULL);
@@ -3422,7 +3427,7 @@ void HeapSnapshotJSONSerializer::Serialize(v8::OutputStream* stream) {
   if (snapshot_->raw_entries_size() >= kMaxSerializableSnapshotRawSize) {
     // The snapshot is too big. Serialize a fake snapshot.
     original_snapshot = snapshot_;
-    snapshot_ = CreateFakeSnapshot();
+    snapshot_ = CreateFakeSnapshot(snapshot_->raw_entries_size());

[mnaganov (inactive), 2012/02/10 12:33:50]

Why can't CreateFakeSnapshot extract this value itself? It is already extracting
other fields from the snapshot.

   }
   // Since nodes graph is cyclic, we need the first pass to enumerate
   // them. Strings can be serialized in one pass.
@@ -3439,15 +3444,22 @@ void HeapSnapshotJSONSerializer::Serialize(v8::OutputStream* stream) {
 }
 
 
-HeapSnapshot* HeapSnapshotJSONSerializer::CreateFakeSnapshot() {
+HeapSnapshot* HeapSnapshotJSONSerializer::CreateFakeSnapshot(
+    int raw_snapshot_size) {
   HeapSnapshot* result = new HeapSnapshot(snapshot_->collection(),
                                           HeapSnapshot::kFull,
                                           snapshot_->title(),
                                           snapshot_->uid());
   result->AllocateEntries(2, 1, 0);
   HeapEntry* root = result->AddRootEntry(1);
+  const char* text = snapshot_->collection()->names()->GetFormatted(
+      "The snapshot is too big. "
+      "Maximum snapshot size is %d MB. "
+      "Actual snapshot size is %d MB.",
+      kMaxSerializableSnapshotRawSize / MB,
+      (raw_snapshot_size + MB - 1) / MB);
   HeapEntry* message = result->AddEntry(
-      HeapEntry::kString, "The snapshot is too big", 0, 4, 0, 0);
+      HeapEntry::kString, text, 0, 4, 0, 0);
   root->SetUnidirElementReference(0, 1, message);
   result->SetDominatorsToSelf();
   return result;