[wrapper-tracing] Add heap snapshot generator infrastructure

third_party/WebKit/Source/bindings/core/v8/V8GCController.cpp

 /*
  * Copyright (C) 2009 Google Inc. 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
@@ skipping 130 matching lines @@
         v8::Persistent<v8::Object>::Cast(*value).MarkActive();
         return;
       }
     }
   }
 
  private:
   v8::Isolate* m_isolate;
 };
 
+class HeapSnaphotWrapperVisitor : public ScriptWrappableVisitor {
+ public:
+  explicit HeapSnaphotWrapperVisitor(v8::Isolate* isolate)
+      : ScriptWrappableVisitor(isolate) {}
+
+  // Trace through the blink heap to find all V8 wrappers reachable from
+  // ActiveScriptWrappables.
+  WTF::HashSet<const v8::PersistentBase<v8::Value>*> findPendingWrappers() {
+    m_foundV8Wrappers.clear();
+
+    TracePrologue();
+    ActiveScriptWrappableBase::traceActiveScriptWrappables(m_isolate, this);
+    AdvanceTracing(
+        0,
+        v8::EmbedderHeapTracer::AdvanceTracingActions(
+            v8::EmbedderHeapTracer::ForceCompletionAction::FORCE_COMPLETION));
+    // Abort instead of Epilogue as we want to finish synchronously.
+    AbortTracing();
+
+    return std::move(m_foundV8Wrappers);
+  }
+
+  // Trace through the blink heap to find all V8 wrappers reachable from
+  // |traceable|.
+  WTF::HashSet<const v8::PersistentBase<v8::Value>*>
+  findV8WrappersReachableFrom(ScriptWrappable* traceable) {
+    m_foundV8Wrappers.clear();
+
+    TracePrologue();
+    traceable->wrapperTypeInfo()->traceWrappers(this, traceable);
+    AdvanceTracing(
+        0,
+        v8::EmbedderHeapTracer::AdvanceTracingActions(
+            v8::EmbedderHeapTracer::ForceCompletionAction::FORCE_COMPLETION));
+    // Abort instead of Epilogue as we want to finish synchronously.
+    AbortTracing();
+
+    return std::move(m_foundV8Wrappers);
+  }
+
+  void markWrapper(const v8::PersistentBase<v8::Value>* value) const override {
+    if (!m_tracingInProgress || m_foundV8Wrappers.contains(value))
+      return;
+    m_foundV8Wrappers.add(value);
+  }
+
+ private:
+  mutable WTF::HashSet<const v8::PersistentBase<v8::Value>*> m_foundV8Wrappers;

[alph, 2017/01/12 08:59:00]

I wonder why not std::unordered_set ?

[Michael Lippautz, 2017/01/12 12:23:19]

Done. Actually I changed the API type to unodred_set so that we can move rather
than copy.

+};
+
+class HeapSnapshotHandlesVisitor : public v8::PersistentHandleVisitor {
+ public:
+  explicit HeapSnapshotHandlesVisitor(v8::Isolate* isolate) {}
+
+  void VisitPersistentHandle(v8::Persistent<v8::Value>* value,
+                             uint16_t classId) override {
+    // TODO: Fill m_nodesRequiringTracing.
+  }
+
+  WTF::HashSet<UntracedMember<Node>> nodesRequiringTracing() {
+    return std::move(m_nodesRequiringTracing);
+  }
+
+ private:
+  WTF::HashSet<UntracedMember<Node>> m_nodesRequiringTracing;
+};
+
+v8::HeapProfiler::RetainerInfos V8GCController::getRetainerInfos(
+    v8::Isolate* isolate) {
+  v8::HeapProfiler::RetainerInfos infos;
+  HeapSnaphotWrapperVisitor tracer(isolate);
+
+  // Find wrappers for pending activities.
+  {
+    V8PerIsolateData::TemporaryScriptWrappableVisitorScope scope(isolate,
+                                                                 &tracer);
+    std::vector<const v8::PersistentBase<v8::Value>*> wrappers;
+    for (auto& wrapper : tracer.findPendingWrappers()) {
+      wrappers.push_back(wrapper);
+    }
+    infos.push_back(std::make_pair(new SuspendableObjectsInfo(wrappers.size()),
+                                   std::move(wrappers)));
+  }
+
+  // Find wrappers for DOM trees.
+  {
+    HeapSnapshotHandlesVisitor visitor(isolate);
+    // TODO
+  }
+
+  return infos;
+}
+
 class MajorGCWrapperVisitor : public v8::PersistentHandleVisitor {
  public:
   explicit MajorGCWrapperVisitor(v8::Isolate* isolate,
                                  bool constructRetainedObjectInfos)
       : m_isolate(isolate),
         m_domObjectsWithPendingActivity(0),
         m_liveRootGroupIdSet(false),
         m_constructRetainedObjectInfos(constructRetainedObjectInfos) {}
 
   void VisitPersistentHandle(v8::Persistent<v8::Value>* value,
@@ skipping 383 matching lines @@
   double startTime = WTF::currentTimeMS();
   v8::HandleScope scope(isolate);
   PendingActivityVisitor visitor(isolate, executionContext);
   toIsolate(executionContext)->VisitHandlesWithClassIds(&visitor);
   scanPendingActivityHistogram.count(
       static_cast<int>(WTF::currentTimeMS() - startTime));
   return visitor.pendingActivityFound();
 }
 
 }  // namespace blink