New heap profiler: implement fast retaining sizes approximation.

include/v8-profiler.h

Index: include/v8-profiler.h
diff --git a/include/v8-profiler.h b/include/v8-profiler.h
index 9b65d0bbfb8b412cbd8915f00b8c66d90d20dd6b..72195c44f2388803d7dbf9f1c44159d409dd769a 100644
--- a/include/v8-profiler.h
+++ b/include/v8-profiler.h
@@ -282,16 +282,19 @@ class V8EXPORT HeapGraphNode {
   /** Returns node's own size, in bytes. */
   int GetSelfSize() const;
 
-  /** Returns node's network (self + reachable nodes) size, in bytes. */
-  int GetReachableSize() const;
-
   /**
    * Returns node's retained size, in bytes. That is, self + sizes of
    * the objects that are reachable only from this object. In other
    * words, the size of memory that will be reclaimed having this node
    * collected.
+   *
+   * Exact retained size calculation has O(N) (number of nodes)
+   * computational complexity, while approximate has O(1). It is
+   * assumed that initially heap profiling tools provide approximate
+   * sizes for all nodes, and then exact sizes are calculated for the
+   * most 'interesting' nodes.
    */
-  int GetRetainedSize() const;
+  int GetRetainedSize(bool exact) const;
 
   /** Returns child nodes count of the node. */
   int GetChildrenCount() const;
@@ -310,6 +313,12 @@ class V8EXPORT HeapGraphNode {
 
   /** Returns a retaining path by index. */
   const HeapGraphPath* GetRetainingPath(int index) const;
+
+  /**
+   * Returns a dominator node. This is the node that participates in every

[Søren Thygesen Gjesse, 2010/11/22 09:49:48]

is the -> is a?

[mnaganov (inactive), 2010/11/22 16:43:56]

Done.

+   * path from the snapshot root to the current node.
+   */
+  const HeapGraphNode* GetDominatorNode() const;
 };