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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/198159">198159</a></dd>
<dt>Author</dt> <dd>commit-queue@webkit.org</dd>
<dt>Date</dt> <dd>2016-03-14 14:50:20 -0700 (Mon, 14 Mar 2016)</dd>
</dl>

<h3>Log Message</h3>
<pre>Reduce generated JSON HeapSnapshot size
https://bugs.webkit.org/show_bug.cgi?id=155460

Patch by Joseph Pecoraro &lt;pecoraro@apple.com&gt; on 2016-03-14
Reviewed by Geoffrey Garen.

Source/JavaScriptCore:

Adjust the HeapSnapshot JSON to better reduce its size.
Changes include:

  - avoid inner array groups and instead just have a large array for
    nodes/edges. This removes lots of small array allocations.
  - eliminate duplicate edges
  - avoid duplicating edge names by including them in their own table;
  - now both the nodes and edges lists hold only integers

* heap/HeapSnapshotBuilder.cpp:
(JSC::HeapSnapshotBuilder::json):
Add some more documentation for the slightly modified format.
While generating, clear data structures as early as possible.

* heap/HeapSnapshotBuilder.h:
(JSC::HeapSnapshotEdge::HeapSnapshotEdge):
During JSON building, the edge's cell pointers are converted to the
identifier they point to. This avoids having to re-lookup the identifier.

* tests/heapProfiler/driver/driver.js:
(CheapHeapSnapshotEdge):
(CheapHeapSnapshot):
(CheapHeapSnapshot.prototype.edgeNameFromTableIndex):
(HeapSnapshot):
Update test driver for slightly different snapshot format.

Source/WebInspectorUI:

* UserInterface/Models/HeapSnapshot.js:
(WebInspector.HeapSnapshot.fromPayload):
Update for the slightly modified format.</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreheapHeapSnapshotBuildercpp">trunk/Source/JavaScriptCore/heap/HeapSnapshotBuilder.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreheapHeapSnapshotBuilderh">trunk/Source/JavaScriptCore/heap/HeapSnapshotBuilder.h</a></li>
<li><a href="#trunkSourceJavaScriptCoretestsheapProfilerdriverdriverjs">trunk/Source/JavaScriptCore/tests/heapProfiler/driver/driver.js</a></li>
<li><a href="#trunkSourceWebInspectorUIChangeLog">trunk/Source/WebInspectorUI/ChangeLog</a></li>
<li><a href="#trunkSourceWebInspectorUIUserInterfaceModelsHeapSnapshotjs">trunk/Source/WebInspectorUI/UserInterface/Models/HeapSnapshot.js</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (198158 => 198159)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog        2016-03-14 21:44:27 UTC (rev 198158)
+++ trunk/Source/JavaScriptCore/ChangeLog        2016-03-14 21:50:20 UTC (rev 198159)
</span><span class="lines">@@ -1,3 +1,36 @@
</span><ins>+2016-03-14  Joseph Pecoraro  &lt;pecoraro@apple.com&gt;
+
+        Reduce generated JSON HeapSnapshot size
+        https://bugs.webkit.org/show_bug.cgi?id=155460
+
+        Reviewed by Geoffrey Garen.
+
+        Adjust the HeapSnapshot JSON to better reduce its size.
+        Changes include:
+
+          - avoid inner array groups and instead just have a large array for
+            nodes/edges. This removes lots of small array allocations.
+          - eliminate duplicate edges
+          - avoid duplicating edge names by including them in their own table;
+          - now both the nodes and edges lists hold only integers
+
+        * heap/HeapSnapshotBuilder.cpp:
+        (JSC::HeapSnapshotBuilder::json):
+        Add some more documentation for the slightly modified format.
+        While generating, clear data structures as early as possible.
+
+        * heap/HeapSnapshotBuilder.h:
+        (JSC::HeapSnapshotEdge::HeapSnapshotEdge):
+        During JSON building, the edge's cell pointers are converted to the
+        identifier they point to. This avoids having to re-lookup the identifier.
+
+        * tests/heapProfiler/driver/driver.js:
+        (CheapHeapSnapshotEdge):
+        (CheapHeapSnapshot):
+        (CheapHeapSnapshot.prototype.edgeNameFromTableIndex):
+        (HeapSnapshot):
+        Update test driver for slightly different snapshot format.
+
</ins><span class="cx"> 2016-03-14  Keith Miller  &lt;keith_miller@apple.com&gt;
</span><span class="cx"> 
</span><span class="cx">         We should be able to eliminate cloned arguments objects that use the length property
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreheapHeapSnapshotBuildercpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/heap/HeapSnapshotBuilder.cpp (198158 => 198159)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/heap/HeapSnapshotBuilder.cpp        2016-03-14 21:44:27 UTC (rev 198158)
+++ trunk/Source/JavaScriptCore/heap/HeapSnapshotBuilder.cpp        2016-03-14 21:50:20 UTC (rev 198159)
</span><span class="lines">@@ -133,22 +133,41 @@
</span><span class="cx"> //   {
</span><span class="cx"> //      &quot;version&quot;: 1.0,
</span><span class="cx"> //      &quot;nodes&quot;: [
</span><del>-//          [&lt;nodeId&gt;, &lt;sizeInBytes&gt;, &lt;nodeClassNameIndex&gt;, &lt;optionalInternal&gt;], ...
</del><ins>+//          &lt;nodeId&gt;, &lt;sizeInBytes&gt;, &lt;nodeClassNameIndex&gt;, &lt;internal&gt;,
+//          &lt;nodeId&gt;, &lt;sizeInBytes&gt;, &lt;nodeClassNameIndex&gt;, &lt;internal&gt;,
+//          ...
</ins><span class="cx"> //      ],
</span><span class="cx"> //      &quot;nodeClassNames&quot;: [
</span><span class="cx"> //          &quot;string&quot;, &quot;Structure&quot;, &quot;Object&quot;, ...
</span><span class="cx"> //      ],
</span><span class="cx"> //      &quot;edges&quot;: [
</span><del>-//          [&lt;fromNodeId&gt;, &lt;toNodeId&gt;, &lt;edgeTypeIndex&gt;, &lt;optionalEdgeExtraData&gt;], ...
</del><ins>+//          &lt;fromNodeId&gt;, &lt;toNodeId&gt;, &lt;edgeTypeIndex&gt;, &lt;edgeExtraData&gt;,
+//          &lt;fromNodeId&gt;, &lt;toNodeId&gt;, &lt;edgeTypeIndex&gt;, &lt;edgeExtraData&gt;,
+//          ...
</ins><span class="cx"> //      ],
</span><span class="cx"> //      &quot;edgeTypes&quot;: [
</span><span class="cx"> //          &quot;Internal&quot;, &quot;Property&quot;, &quot;Index&quot;, &quot;Variable&quot;
</span><ins>+//      ],
+//      &quot;edgeNames&quot;: [
+//          &quot;propertyName&quot;, &quot;variableName&quot;, ...
</ins><span class="cx"> //      ]
</span><span class="cx"> //   }
</span><span class="cx"> //
</span><del>-// FIXME: Possible compaction improvements:
-//   - eliminate inner array groups and just have a single list with fixed group sizes (meta data section).
-//   - eliminate duplicate edge extra data strings, have an index into a de-duplicated like edgeTypes / nodeClassNames.
</del><ins>+// Notes:
+//
+//     &lt;nodeClassNameIndex&gt;
+//       - index into the &quot;nodeClassNames&quot; list.
+//
+//     &lt;internal&gt;
+//       - 0 = false, 1 = true.
+//
+//     &lt;edgeTypeIndex&gt;
+//       - index into the &quot;edgeTypes&quot; list.
+//
+//     &lt;edgeExtraData&gt;
+//       - for Internal edges this should be ignored (0).
+//       - for Index edges this is the index value.
+//       - for Property or Variable edges this is an index into the &quot;edgeNames&quot; list.
</ins><span class="cx"> 
</span><span class="cx"> static uint8_t edgeTypeToNumber(EdgeType type)
</span><span class="cx"> {
</span><span class="lines">@@ -186,8 +205,13 @@
</span><span class="cx"> 
</span><span class="cx">     // Build a list of used class names.
</span><span class="cx">     HashMap&lt;const char*, unsigned&gt; classNameIndexes;
</span><del>-    unsigned nextClassNameIndex = 0;
</del><ins>+    classNameIndexes.set(&quot;&lt;root&gt;&quot;, 0);
+    unsigned nextClassNameIndex = 1;
</ins><span class="cx"> 
</span><ins>+    // Build a list of used edge names.
+    HashMap&lt;UniquedStringImpl*, unsigned&gt; edgeNameIndexes;
+    unsigned nextEdgeNameIndex = 0;
+
</ins><span class="cx">     StringBuilder json;
</span><span class="cx"> 
</span><span class="cx">     auto appendNodeJSON = [&amp;] (const HeapSnapshotNode&amp; node) {
</span><span class="lines">@@ -208,64 +232,48 @@
</span><span class="cx">             isInternal = !structure || !structure-&gt;globalObject();
</span><span class="cx">         }
</span><span class="cx"> 
</span><del>-        // [&lt;nodeId&gt;, &lt;sizeInBytes&gt;, &lt;className&gt;, &lt;optionalInternalBoolean&gt;]
</del><ins>+        // &lt;nodeId&gt;, &lt;sizeInBytes&gt;, &lt;className&gt;, &lt;optionalInternalBoolean&gt;
</ins><span class="cx">         json.append(',');
</span><del>-        json.append('[');
</del><span class="cx">         json.appendNumber(node.identifier);
</span><span class="cx">         json.append(',');
</span><span class="cx">         json.appendNumber(node.cell-&gt;estimatedSizeInBytes());
</span><span class="cx">         json.append(',');
</span><span class="cx">         json.appendNumber(classNameIndex);
</span><del>-        if (isInternal)
-            json.appendLiteral(&quot;,1&quot;);
-        json.append(']');
</del><ins>+        json.append(',');
+        json.append(isInternal ? '1' : '0');
</ins><span class="cx">     };
</span><span class="cx"> 
</span><span class="cx">     bool firstEdge = true;
</span><span class="cx">     auto appendEdgeJSON = [&amp;] (const HeapSnapshotEdge&amp; edge) {
</span><del>-        // If the from cell is null, this means a root edge.
-        unsigned fromIdentifier = 0;
-        if (edge.from) {
-            auto fromLookup = allowedNodeIdentifiers.find(edge.from);
-            if (fromLookup == allowedNodeIdentifiers.end())
-                return;
-            fromIdentifier = fromLookup-&gt;value;
-        }
-
-        unsigned toIdentifier = 0;
-        if (edge.to) {
-            auto toLookup = allowedNodeIdentifiers.find(edge.to);
-            if (toLookup == allowedNodeIdentifiers.end())
-                return;
-            toIdentifier = toLookup-&gt;value;
-        }
-
</del><span class="cx">         if (!firstEdge)
</span><span class="cx">             json.append(',');
</span><span class="cx">         firstEdge = false;
</span><span class="cx"> 
</span><del>-        // [&lt;fromNodeId&gt;, &lt;toNodeId&gt;, &lt;edgeTypeIndex&gt;, &lt;optionalEdgeExtraData&gt;],
-        json.append('[');
-        json.appendNumber(fromIdentifier);
</del><ins>+        // &lt;fromNodeId&gt;, &lt;toNodeId&gt;, &lt;edgeTypeIndex&gt;, &lt;edgeExtraData&gt;
+        json.appendNumber(edge.from.identifier);
</ins><span class="cx">         json.append(',');
</span><del>-        json.appendNumber(toIdentifier);
</del><ins>+        json.appendNumber(edge.to.identifier);
</ins><span class="cx">         json.append(',');
</span><span class="cx">         json.appendNumber(edgeTypeToNumber(edge.type));
</span><ins>+        json.append(',');
</ins><span class="cx">         switch (edge.type) {
</span><span class="cx">         case EdgeType::Property:
</span><del>-        case EdgeType::Variable:
-            json.append(',');
-            json.appendQuotedJSONString(edge.u.name);
</del><ins>+        case EdgeType::Variable: {
+            auto result = edgeNameIndexes.add(edge.u.name, nextEdgeNameIndex);
+            if (result.isNewEntry)
+                nextEdgeNameIndex++;
+            unsigned edgeNameIndex = result.iterator-&gt;value;
+            json.appendNumber(edgeNameIndex);
</ins><span class="cx">             break;
</span><ins>+        }
</ins><span class="cx">         case EdgeType::Index:
</span><del>-            json.append(',');
</del><span class="cx">             json.appendNumber(edge.u.index);
</span><span class="cx">             break;
</span><span class="cx">         default:
</span><span class="cx">             // No data for this edge type.
</span><ins>+            json.append('0');
</ins><span class="cx">             break;
</span><span class="cx">         }
</span><del>-        json.append(']');
</del><span class="cx">     };
</span><span class="cx"> 
</span><span class="cx">     json.append('{');
</span><span class="lines">@@ -277,7 +285,7 @@
</span><span class="cx">     json.append(',');
</span><span class="cx">     json.appendLiteral(&quot;\&quot;nodes\&quot;:&quot;);
</span><span class="cx">     json.append('[');
</span><del>-    json.appendLiteral(&quot;[0,0,\&quot;&lt;root&gt;\&quot;]&quot;);
</del><ins>+    json.appendLiteral(&quot;0,0,0,0&quot;); // &lt;root&gt;
</ins><span class="cx">     for (HeapSnapshot* snapshot = m_profiler.mostRecentSnapshot(); snapshot; snapshot = snapshot-&gt;previous()) {
</span><span class="cx">         for (auto&amp; node : snapshot-&gt;m_nodes)
</span><span class="cx">             appendNodeJSON(node);
</span><span class="lines">@@ -291,6 +299,7 @@
</span><span class="cx">     Vector&lt;const char *&gt; orderedClassNames(classNameIndexes.size());
</span><span class="cx">     for (auto&amp; entry : classNameIndexes)
</span><span class="cx">         orderedClassNames[entry.value] = entry.key;
</span><ins>+    classNameIndexes.clear();
</ins><span class="cx">     bool firstClassName = true;
</span><span class="cx">     for (auto&amp; className : orderedClassNames) {
</span><span class="cx">         if (!firstClassName)
</span><span class="lines">@@ -298,8 +307,42 @@
</span><span class="cx">         firstClassName = false;
</span><span class="cx">         json.appendQuotedJSONString(className);
</span><span class="cx">     }
</span><ins>+    orderedClassNames.clear();
</ins><span class="cx">     json.append(']');
</span><span class="cx"> 
</span><ins>+    // Process edges.
+    // Replace pointers with identifiers.
+    // Remove any edges that we won't need.
+    m_edges.removeAllMatching([&amp;] (HeapSnapshotEdge&amp; edge) {
+        // If the from cell is null, this means a &lt;root&gt; edge.
+        if (!edge.from.cell)
+            edge.from.identifier = 0;
+        else {
+            auto fromLookup = allowedNodeIdentifiers.find(edge.from.cell);
+            if (fromLookup == allowedNodeIdentifiers.end())
+                return true;
+            edge.from.identifier = fromLookup-&gt;value;
+        }
+
+        if (!edge.to.cell)
+            edge.to.identifier = 0;
+        else {
+            auto toLookup = allowedNodeIdentifiers.find(edge.to.cell);
+            if (toLookup == allowedNodeIdentifiers.end())
+                return true;
+            edge.to.identifier = toLookup-&gt;value;
+        }
+
+        return false;
+    });
+    allowedNodeIdentifiers.clear();
+    m_edges.shrinkToFit();
+
+    // Sort edges based on from identifier.
+    std::sort(m_edges.begin(), m_edges.end(), [&amp;] (const HeapSnapshotEdge&amp; a, const HeapSnapshotEdge&amp; b) {
+        return a.from.identifier &lt; b.from.identifier;
+    });
+
</ins><span class="cx">     // edges
</span><span class="cx">     json.append(',');
</span><span class="cx">     json.appendLiteral(&quot;\&quot;edges\&quot;:&quot;);
</span><span class="lines">@@ -321,6 +364,24 @@
</span><span class="cx">     json.appendQuotedJSONString(edgeTypeToString(EdgeType::Variable));
</span><span class="cx">     json.append(']');
</span><span class="cx"> 
</span><ins>+    // edge names
+    json.append(',');
+    json.appendLiteral(&quot;\&quot;edgeNames\&quot;:&quot;);
+    json.append('[');
+    Vector&lt;UniquedStringImpl*&gt; orderedEdgeNames(edgeNameIndexes.size());
+    for (auto&amp; entry : edgeNameIndexes)
+        orderedEdgeNames[entry.value] = entry.key;
+    edgeNameIndexes.clear();
+    bool firstEdgeName = true;
+    for (auto&amp; edgeName : orderedEdgeNames) {
+        if (!firstEdgeName)
+            json.append(',');
+        firstEdgeName = false;
+        json.appendQuotedJSONString(edgeName);
+    }
+    orderedEdgeNames.clear();
+    json.append(']');
+
</ins><span class="cx">     json.append('}');
</span><span class="cx">     return json.toString();
</span><span class="cx"> }
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreheapHeapSnapshotBuilderh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/heap/HeapSnapshotBuilder.h (198158 => 198159)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/heap/HeapSnapshotBuilder.h        2016-03-14 21:44:27 UTC (rev 198158)
+++ trunk/Source/JavaScriptCore/heap/HeapSnapshotBuilder.h        2016-03-14 21:50:20 UTC (rev 198159)
</span><span class="lines">@@ -57,36 +57,46 @@
</span><span class="cx"> };
</span><span class="cx"> 
</span><span class="cx"> struct HeapSnapshotEdge {
</span><del>-    HeapSnapshotEdge(JSCell* from, JSCell* to)
-        : from(from)
-        , to(to)
-        , type(EdgeType::Internal)
-    { }
</del><ins>+    HeapSnapshotEdge(JSCell* fromCell, JSCell* toCell)
+        : type(EdgeType::Internal)
+    {
+        from.cell = fromCell;
+        to.cell = toCell;
+    }
</ins><span class="cx"> 
</span><del>-    HeapSnapshotEdge(JSCell* from, JSCell* to, EdgeType type, UniquedStringImpl* name)
-        : from(from)
-        , to(to)
-        , type(type)
</del><ins>+    HeapSnapshotEdge(JSCell* fromCell, JSCell* toCell, EdgeType type, UniquedStringImpl* name)
+        : type(type)
</ins><span class="cx">     {
</span><span class="cx">         ASSERT(type == EdgeType::Property || type == EdgeType::Variable);
</span><ins>+        from.cell = fromCell;
+        to.cell = toCell;
</ins><span class="cx">         u.name = name;
</span><span class="cx">     }
</span><span class="cx"> 
</span><del>-    HeapSnapshotEdge(JSCell* from, JSCell* to, uint32_t index)
-        : from(from)
-        , to(to)
-        , type(EdgeType::Index)
</del><ins>+    HeapSnapshotEdge(JSCell* fromCell, JSCell* toCell, uint32_t index)
+        : type(EdgeType::Index)
</ins><span class="cx">     {
</span><ins>+        from.cell = fromCell;
+        to.cell = toCell;
</ins><span class="cx">         u.index = index;
</span><span class="cx">     }
</span><span class="cx"> 
</span><del>-    JSCell* from;
-    JSCell* to;
-    EdgeType type;
</del><span class="cx">     union {
</span><ins>+        JSCell *cell;
+        unsigned identifier;
+    } from;
+
+    union {
+        JSCell *cell;
+        unsigned identifier;
+    } to;
+
+    union {
</ins><span class="cx">         UniquedStringImpl* name;
</span><span class="cx">         uint32_t index;
</span><span class="cx">     } u;
</span><ins>+
+    EdgeType type;
</ins><span class="cx"> };
</span><span class="cx"> 
</span><span class="cx"> class JS_EXPORT_PRIVATE HeapSnapshotBuilder {
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoretestsheapProfilerdriverdriverjs"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/tests/heapProfiler/driver/driver.js (198158 => 198159)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/tests/heapProfiler/driver/driver.js        2016-03-14 21:44:27 UTC (rev 198158)
+++ trunk/Source/JavaScriptCore/tests/heapProfiler/driver/driver.js        2016-03-14 21:50:20 UTC (rev 198159)
</span><span class="lines">@@ -18,7 +18,7 @@
</span><span class="cx"> const nodeFirstEdgeOffset = 4;
</span><span class="cx"> const nodeNoEdgeValue = 0xffffffff; // UINT_MAX
</span><span class="cx"> 
</span><del>-// [&lt;0:from-id&gt;, &lt;1:to-id&gt;, &lt;2:typeTableIndex&gt;, &lt;3:data&gt;]
</del><ins>+// [&lt;0:fromId&gt;, &lt;1:toId&gt;, &lt;2:typeTableIndex&gt;, &lt;3:edgeDataIndexOrEdgeNameIndex&gt;]
</ins><span class="cx"> const edgeFieldCount = 4;
</span><span class="cx"> const edgeFromIdOffset = 0;
</span><span class="cx"> const edgeToIdOffset = 1;
</span><span class="lines">@@ -60,7 +60,11 @@
</span><span class="cx">         this.fromId = edges[edgeIndex + edgeFromIdOffset];
</span><span class="cx">         this.toId = edges[edgeIndex + edgeToIdOffset];
</span><span class="cx">         this.type = snapshot.edgeTypeFromTableIndex(edges[edgeIndex + edgeTypeOffset]);
</span><del>-        this.data = edges[edgeIndex + edgeDataOffset];
</del><ins>+
+        if (this.type === &quot;Property&quot; || this.type === &quot;Variable&quot;)
+            this.data = snapshot.edgeNameFromTableIndex(edges[edgeIndex + edgeDataOffset]);
+        else
+            this.data = edges[edgeIndex + edgeDataOffset];
</ins><span class="cx">     }
</span><span class="cx"> 
</span><span class="cx">     get from() { return this.snapshot.nodeWithIdentifier(this.fromId); }
</span><span class="lines">@@ -71,41 +75,44 @@
</span><span class="cx"> {
</span><span class="cx">     constructor(json)
</span><span class="cx">     {
</span><del>-        let {nodes, nodeClassNames, edges, edgeTypes} = json;
</del><ins>+        let {nodes, nodeClassNames, edges, edgeTypes, edgeNames} = json;
</ins><span class="cx"> 
</span><span class="cx">         this._nodes = new Uint32Array(nodes.length * nodeFieldCount);
</span><span class="cx">         this._edges = new Uint32Array(edges.length * edgeFieldCount);
</span><span class="cx">         this._nodeIdentifierToIndex = new Map; // &lt;id&gt; =&gt; index in _nodes
</span><span class="cx"> 
</span><span class="cx">         this._edgeTypesTable = edgeTypes;
</span><ins>+        this._edgeNamesTable = edgeNames;
</ins><span class="cx">         this._nodeClassNamesTable = nodeClassNames;
</span><span class="cx"> 
</span><span class="cx">         let n = 0;
</span><del>-        nodes.forEach((nodePayload) =&gt; {
-            let [id, size, classNameTableIndex, internal] = nodePayload;
-            this._nodeIdentifierToIndex.set(id, n);
-            this._nodes[n++] = id;
-            this._nodes[n++] = size;
-            this._nodes[n++] = classNameTableIndex;
-            this._nodes[n++] = internal;
</del><ins>+        for (let i = 0; i &lt; nodes.length;) {
+            this._nodeIdentifierToIndex.set(nodes[i], n);
+            this._nodes[n++] = nodes[i++]; // id
+            this._nodes[n++] = nodes[i++]; // size
+            this._nodes[n++] = nodes[i++]; // classNameTableIndex
+            this._nodes[n++] = nodes[i++]; // internal
</ins><span class="cx">             this._nodes[n++] = nodeNoEdgeValue;
</span><del>-        });
</del><ins>+        }
</ins><span class="cx"> 
</span><span class="cx">         let e = 0;
</span><span class="cx">         let lastNodeIdentifier = -1;
</span><del>-        edges.sort((a, b) =&gt; a[0] - b[0]).forEach((edgePayload) =&gt; {
-            let [fromIdentifier, toIdentifier, edgeTypeTableIndex, data] = edgePayload;
</del><ins>+        for (let i = 0; i &lt; edges.length;) {
+            let fromIdentifier = edges[i++]; // fromIdentifier
+            let toIdentifier = edges[i++]; // toIdentifier
+            assert(lastNodeIdentifier &lt;= fromIdentifier, &quot;Edge list should be ordered by from node identifier&quot;);
</ins><span class="cx">             if (fromIdentifier !== lastNodeIdentifier) {
</span><span class="cx">                 let nodeIndex = this._nodeIdentifierToIndex.get(fromIdentifier);
</span><span class="cx">                 assert(this._nodes[nodeIndex + nodeIdOffset] === fromIdentifier, &quot;Node lookup failed&quot;);
</span><span class="cx">                 this._nodes[nodeIndex + nodeFirstEdgeOffset] = e;
</span><span class="cx">                 lastNodeIdentifier = fromIdentifier;
</span><span class="cx">             }
</span><ins>+
</ins><span class="cx">             this._edges[e++] = fromIdentifier;
</span><span class="cx">             this._edges[e++] = toIdentifier;
</span><del>-            this._edges[e++] = edgeTypeTableIndex;
-            this._edges[e++] = data;
-        });
</del><ins>+            this._edges[e++] = edges[i++]; // edgeTypeTableIndex
+            this._edges[e++] = edges[i++]; // data
+        }
</ins><span class="cx">     }
</span><span class="cx"> 
</span><span class="cx">     get nodes() { return this._nodes; }
</span><span class="lines">@@ -136,6 +143,11 @@
</span><span class="cx">     {
</span><span class="cx">         return this._edgeTypesTable[tableIndex];
</span><span class="cx">     }
</span><ins>+
+    edgeNameFromTableIndex(tableIndex)
+    {
+        return this._edgeNamesTable[tableIndex];
+    }
</ins><span class="cx"> }
</span><span class="cx"> 
</span><span class="cx"> function createCheapHeapSnapshot() {
</span><span class="lines">@@ -189,27 +201,39 @@
</span><span class="cx"> {
</span><span class="cx">     constructor(json)
</span><span class="cx">     {        
</span><del>-        let {version, nodes, nodeClassNames, edges, edgeTypes} = json;
</del><ins>+        let {version, nodes, nodeClassNames, edges, edgeTypes, edgeNames} = json;
</ins><span class="cx"> 
</span><span class="cx">         this.nodeMap = new Map;
</span><span class="cx"> 
</span><del>-        this.nodes = nodes.map((nodePayload) =&gt; {
-            let [id, size, classNameIndex, internal] = nodePayload;
</del><ins>+        this.nodes = [];
+        for (let i = 0; i &lt; nodes.length;) {
+            let id = nodes[i++];
+            let size = nodes[i++];
+            let classNameIndex = nodes[i++];
+            let internal = nodes[i++];
+
</ins><span class="cx">             let node = new HeapSnapshotNode(id, nodeClassNames[classNameIndex], size, internal);
</span><span class="cx">             this.nodeMap.set(id, node);
</span><del>-            return node;
-        });
</del><ins>+            this.nodes.push(node);
+        }
</ins><span class="cx"> 
</span><del>-        edges.map((edgePayload) =&gt; {
-            let [fromIdentifier, toIdentifier, edgeTypeIndex, data] = edgePayload;
</del><ins>+        for (let i = 0; i &lt; edges.length;) {
+            let fromIdentifier = edges[i++];
+            let toIdentifier = edges[i++];
+            let edgeTypeIndex = edges[i++];
+            let data = edges[i++];
+
</ins><span class="cx">             let from = this.nodeMap.get(fromIdentifier);
</span><span class="cx">             let to = this.nodeMap.get(toIdentifier);
</span><span class="cx">             assert(from, &quot;Missing node for `from` part of edge&quot;);
</span><span class="cx">             assert(to, &quot;Missing node for `to` part of edge&quot;);
</span><ins>+            let type = edgeTypes[edgeTypeIndex];
+            if (type === &quot;Property&quot; || type === &quot;Variable&quot;)
+                data = edgeNames[data];
</ins><span class="cx">             let edge = new HeapSnapshotEdge(from, to, edgeTypes[edgeTypeIndex], data);
</span><span class="cx">             from.outgoingEdges.push(edge);
</span><span class="cx">             to.incomingEdges.push(edge);
</span><del>-        });
</del><ins>+        }
</ins><span class="cx"> 
</span><span class="cx">         this.rootNode = this.nodeMap.get(0);
</span><span class="cx">         assert(this.rootNode, &quot;Missing &lt;root&gt; node with identifier 0&quot;);
</span></span></pre></div>
<a id="trunkSourceWebInspectorUIChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebInspectorUI/ChangeLog (198158 => 198159)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebInspectorUI/ChangeLog        2016-03-14 21:44:27 UTC (rev 198158)
+++ trunk/Source/WebInspectorUI/ChangeLog        2016-03-14 21:50:20 UTC (rev 198159)
</span><span class="lines">@@ -1,3 +1,14 @@
</span><ins>+2016-03-14  Joseph Pecoraro  &lt;pecoraro@apple.com&gt;
+
+        Reduce generated JSON HeapSnapshot size
+        https://bugs.webkit.org/show_bug.cgi?id=155460
+
+        Reviewed by Geoffrey Garen.
+
+        * UserInterface/Models/HeapSnapshot.js:
+        (WebInspector.HeapSnapshot.fromPayload):
+        Update for the slightly modified format.
+
</ins><span class="cx"> 2016-03-14  Commit Queue  &lt;commit-queue@webkit.org&gt;
</span><span class="cx"> 
</span><span class="cx">         Unreviewed, rolling out r198095.
</span></span></pre></div>
<a id="trunkSourceWebInspectorUIUserInterfaceModelsHeapSnapshotjs"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebInspectorUI/UserInterface/Models/HeapSnapshot.js (198158 => 198159)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebInspectorUI/UserInterface/Models/HeapSnapshot.js        2016-03-14 21:44:27 UTC (rev 198158)
+++ trunk/Source/WebInspectorUI/UserInterface/Models/HeapSnapshot.js        2016-03-14 21:50:20 UTC (rev 198159)
</span><span class="lines">@@ -77,36 +77,39 @@
</span><span class="cx"> 
</span><span class="cx">     static fromPayload(payload)
</span><span class="cx">     {
</span><del>-        let {version, nodes, nodeClassNames, edges, edgeTypes} = payload;
</del><ins>+        let {version, nodes, nodeClassNames, edges, edgeTypes, edgeNames} = payload;
</ins><span class="cx">         console.assert(version === 1, &quot;Only know how to handle JavaScriptCore Heap Snapshot Format Version 1&quot;);
</span><span class="cx">         console.assert(edgeTypes.every((type) =&gt; type in WebInspector.HeapSnapshotEdge.EdgeType), &quot;Unexpected edge type&quot;, edgeTypes);
</span><span class="cx"> 
</span><span class="cx">         let nodeMap = new Map;
</span><span class="cx"> 
</span><span class="cx">         // Turn nodes into real nodes.
</span><del>-        for (let i = 0, length = nodes.length; i &lt; length; ++i) {
-            let nodePayload = nodes[i];
-            let id = nodePayload[0];
-            let size = nodePayload[1];
-            let classNameIndex = nodePayload[2];
-            let internal = nodePayload[3];
</del><ins>+        let processedNodes = [];
+        for (let i = 0, length = nodes.length; i &lt; length;) {
+            let id = nodes[i++];
+            let size = nodes[i++];
+            let classNameIndex = nodes[i++];
+            let internal = nodes[i++];
</ins><span class="cx"> 
</span><span class="cx">             let node = new WebInspector.HeapSnapshotNode(id, nodeClassNames[classNameIndex], size, !!internal);
</span><span class="cx">             nodeMap.set(id, node);
</span><del>-            nodes[i] = node;
</del><ins>+            processedNodes.push(node);
</ins><span class="cx">         }
</span><span class="cx"> 
</span><span class="cx">         // Turn edges into real edges and set them on the nodes.
</span><del>-        for (let i = 0, length = edges.length; i &lt; length; ++i) {
-            let edgePayload = edges[i];
-            let fromIdentifier = edgePayload[0];
-            let toIdentifier = edgePayload[1];
-            let edgeTypeIndex = edgePayload[2];
-            let data = edgePayload[3];
</del><ins>+        for (let i = 0, length = edges.length; i &lt; length;) {
+            let fromIdentifier = edges[i++];
+            let toIdentifier = edges[i++];
+            let edgeTypeIndex = edges[i++];
+            let data = edges[i++];
</ins><span class="cx"> 
</span><span class="cx">             let from = nodeMap.get(fromIdentifier);
</span><span class="cx">             let to = nodeMap.get(toIdentifier);
</span><del>-            let edge = new WebInspector.HeapSnapshotEdge(from, to, edgeTypes[edgeTypeIndex], data);
</del><ins>+            let type = edgeTypes[edgeTypeIndex];
+            if (type === WebInspector.HeapSnapshotEdge.EdgeType.Property || type === WebInspector.HeapSnapshotEdge.EdgeType.Variable)
+                data = edgeNames[data];
+
+            let edge = new WebInspector.HeapSnapshotEdge(from, to, type, data);
</ins><span class="cx">             from.outgoingEdges.push(edge);
</span><span class="cx">             to.incomingEdges.push(edge);
</span><span class="cx">         }
</span><span class="lines">@@ -122,7 +125,7 @@
</span><span class="cx">         for (let i = 0, length = rootNodeEdges.length; i &lt; length; ++i)
</span><span class="cx">             rootNodeEdges[i].to.gcRoot = true;
</span><span class="cx"> 
</span><del>-        return new WebInspector.HeapSnapshot(rootNode, nodes, nodeMap);
</del><ins>+        return new WebInspector.HeapSnapshot(rootNode, processedNodes, nodeMap);
</ins><span class="cx">     }
</span><span class="cx"> 
</span><span class="cx">     // Public
</span></span></pre>
</div>
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