[heap] Rework and improve object stats tracing

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index 51d114a7ab047da667134fae6de4907d2f8d34f1..f153634c9c9d5719592eeee2429bad584f7bedcb 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -326,7 +326,6 @@ void MarkCompactCollector::ClearInvalidRememberedSetSlots() {
 #endif
 }
 
-
 void MarkCompactCollector::CollectGarbage() {
   // Make sure that Prepare() has been called. The individual steps below will
   // update the state as they proceed.
@@ -1302,10 +1301,6 @@ void MarkCompactMarkingVisitor::Initialize() {
   StaticMarkingVisitor<MarkCompactMarkingVisitor>::Initialize();
 
   table_.Register(kVisitJSRegExp, &VisitRegExpAndFlushCode);
-
-  if (FLAG_track_gc_object_stats) {
-    MarkCompactObjectStatsVisitor::Initialize(&table_);
-  }
 }
 
 
@@ -2282,6 +2277,39 @@ void MarkCompactCollector::RegisterExternallyReferencedObject(Object** object) {
   MarkObject(heap_object, mark_bit);
 }
 
+class MarkCompactCollector::ObjectStatsVisitor
+    : public MarkCompactCollector::HeapObjectVisitor {
+ public:
+  ObjectStatsVisitor(ObjectStats* live_stats, ObjectStats* dead_stats)
+      : live_stats_(live_stats), dead_stats_(dead_stats) {}
+
+  bool Visit(HeapObject* obj) override {
+    if (Marking::IsBlack(Marking::MarkBitFrom(obj))) {
+      if (live_stats_ != nullptr)
+        ObjectStatsCollector::CollectStatistics(live_stats_, obj);
+    } else {
+      if (dead_stats_ != nullptr)
+        ObjectStatsCollector::CollectStatistics(dead_stats_, obj);
+    }
+    return true;
+  }
+
+ private:
+  ObjectStats* live_stats_;
+  ObjectStats* dead_stats_;
+};
+
+void MarkCompactCollector::VisitAllObjects(HeapObjectVisitor* visitor) {
+  SpaceIterator space_it(heap());

[Michael Lippautz, 2016/07/13 10:10:00]

Hannes: Your HeapObjectIterator changes have been reverted, so it still causes a
GC and we cannot use it.

[Hannes Payer (out of office), 2016/07/13 11:39:11]

Yeah, for snapshot reasons. Just use your custom iterator.

[Michael Lippautz, 2016/07/13 12:20:17]

Acknowledged.

+  HeapObject* obj = nullptr;
+  while (space_it.has_next()) {
+    ObjectIterator* it = space_it.next();
+    while ((obj = it->Next()) != nullptr) {
+      visitor->Visit(obj);
+    }
+  }
+}
+
 void MarkCompactCollector::MarkLiveObjects() {
   TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK);
   double start_time = 0.0;
@@ -2301,10 +2329,6 @@ void MarkCompactCollector::MarkLiveObjects() {
     } else {
       // Abort any pending incremental activities e.g. incremental sweeping.
       incremental_marking->Stop();
-      if (FLAG_track_gc_object_stats) {
-        // Clear object stats collected during incremental marking.
-        heap()->object_stats_->ClearObjectStats();
-      }
       if (marking_deque_.in_use()) {
         marking_deque_.Uninitialize(true);
       }
@@ -2387,7 +2411,16 @@ void MarkCompactCollector::MarkLiveObjects() {
   }
   if (FLAG_track_gc_object_stats) {
     if (FLAG_trace_gc_object_stats) {
-      heap()->object_stats_->TraceObjectStats();
+      // Reuse the live stats that are already recorded with
+      // --track_gc_object_stats.
+      ObjectStats dead_stats(heap());
+      ObjectStatsVisitor visitor(heap()->object_stats_, &dead_stats);
+      VisitAllObjects(&visitor);
+      heap()->object_stats_->PrintJSON("live");
+      dead_stats.PrintJSON("dead");
+    } else {
+      ObjectStatsVisitor visitor(heap()->object_stats_, nullptr);
+      VisitAllObjects(&visitor);
     }
     heap()->object_stats_->CheckpointObjectStats();
   }