Oilpan: Schedule a precise GC when a page navigates

Source/core/loader/FrameLoader.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008 Alp Toker <alp@atoker.com>
  * Copyright (C) Research In Motion Limited 2009. All rights reserved.
  * Copyright (C) 2011 Kris Jordan <krisjordan@gmail.com>
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ skipping 1005 matching lines @@
 }
 
 void FrameLoader::notifyIfInitialDocumentAccessed()
 {
     if (m_didAccessInitialDocumentTimer.isActive()) {
         m_didAccessInitialDocumentTimer.stop();
         didAccessInitialDocumentTimerFired(0);
     }
 }
 
 bool FrameLoader::prepareForCommit()

[haraken, 2015/07/23 23:19:30]

Just a question: When will prepareForCommit() be called? Is it before
WindowProxy::closeForNavigation() or after WindowProxy::closeForNavigation()?

 {
     PluginScriptForbiddenScope forbidPluginDestructorScripting;
     RefPtrWillBeRawPtr<DocumentLoader> pdl = m_provisionalDocumentLoader;
 
+    if (m_frame->document()) {
+        unsigned nodeCount = 0;
+        for (Frame* frame = m_frame; frame; frame = frame->tree().traverseNext()) {
+            if (frame->isLocalFrame())
+                nodeCount += m_frame->domWindow()->document()->nodeCount();

[haraken, 2015/07/23 23:19:30]

If things happen in the order of:

1) User script removes all nodes from a document.
2) The document navigates away.

then the node count reported here would be underestimated. I think you were
saying that this is happening in Speedometer.

I guess what we really want to count here is (the number of nodes attached to
the document) + (the number of nodes that are not attached to any document).
Maybe we can count the number by hooking the following functions.

- Node's constructor  -- A
- Node's destructor  -- B
- Node::insertedInto  -- C(i)
- Node::removedFrom  -- D(i)

Then:

(the number of nodes attached to the document) + (the number of nodes that are
not attached to any document x) = (A - B - \sum (C(i) - D(i))) + (C(x) - D(x))

+        }
+        float ratio = static_cast<float>(nodeCount) / InstanceCounters::counterValue(InstanceCounters::NodeCounter);
+        if (ratio > 1)

[haraken, 2015/07/23 23:19:30]

When can this happen?

+            ratio = 1;
+        if (ThreadState::current()->shouldSchedulePreciseGCOnNavigation(ratio))
+            ThreadState::current()->schedulePreciseGC();
+    }
+
     if (m_documentLoader) {
         client()->dispatchWillClose();
         dispatchUnloadEvent();
     }
     m_frame->detachChildren();
     // The previous calls to dispatchUnloadEvent() and detachChildren() can
     // execute arbitrary script via things like unload events. If the executed
     // script intiates a new load or causes the current frame to be detached,
     // we need to abandon the current load.
     if (pdl != m_provisionalDocumentLoader)
@@ skipping 453 matching lines @@
     // FIXME: We need a way to propagate insecure requests policy flags to
     // out-of-process frames. For now, we'll always use default behavior.
     if (!parentFrame->isLocalFrame())
         return nullptr;
 
     ASSERT(toLocalFrame(parentFrame)->document());
     return toLocalFrame(parentFrame)->document()->insecureNavigationsToUpgrade();
 }
 
 } // namespace blink