Heap snapshot visualizations

runtime/vm/service.cc

Index: runtime/vm/service.cc
diff --git a/runtime/vm/service.cc b/runtime/vm/service.cc
index 074c1925d405a6487bde5a710645c60f3e86e5fe..e40d39bea7f179a24628d539a1b7a84d7972fbf4 100644
--- a/runtime/vm/service.cc
+++ b/runtime/vm/service.cc
@@ -2252,19 +2252,35 @@ void Service::SendGraphEvent(Isolate* isolate) {
   uint8_t* buffer = NULL;
   WriteStream stream(&buffer, &allocator, 1 * MB);
   ObjectGraph graph(isolate);
-  graph.Serialize(&stream);
-  JSONStream js;
-  {
-    JSONObject jsobj(&js);
+  intptr_t node_count = graph.Serialize(&stream);
+
+  // Chrome crashes receiving a single tens-of-megabytes blob, so send the
+  // snapshot in megabyte-sized chunks instead.

[koda, 2015/05/19 20:12:36]

Add named constant for chunk size.

[rmacnak, 2015/05/19 22:16:08]

Done.

+  intptr_t num_chunks = (stream.bytes_written() + (MB - 1)) / MB;
+  for (intptr_t i = 0; i < num_chunks; i++) {
+    JSONStream js;
     {
-      JSONObject event(&jsobj, "event");
-      event.AddProperty("type", "ServiceEvent");
-      event.AddProperty("eventType", "_Graph");
-      event.AddProperty("isolate", isolate);
+      JSONObject jsobj(&js);
+      {
+        JSONObject event(&jsobj, "event");
+        event.AddProperty("type", "ServiceEvent");
+        event.AddProperty("eventType", "_Graph");
+        event.AddProperty("isolate", isolate);
+
+        event.AddProperty("i", i);
+        event.AddProperty("n", num_chunks);
+        event.AddProperty("nodeCount", node_count);
+      }
     }
+    const String& message = String::Handle(String::New(js.ToCString()));
+
+    uint8_t* chunk_start = buffer + (i * MB);
+    intptr_t chunk_size = (i + 1 == num_chunks)

[koda, 2015/05/19 20:12:35]

Does this do the right thing when the last chunk is exactly 1 MB? The remainder
will be 0.

[rmacnak, 2015/05/19 22:16:08]

No, fixed.

+      ? stream.bytes_written() % MB
+      : MB;
+
+    SendEvent(message, chunk_start, chunk_size);
   }
-  const String& message = String::Handle(String::New(js.ToCString()));
-  SendEvent(message, buffer, stream.bytes_written());
 }