[heap] Rework and improve object stats tracing

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 308 matching lines @@
 // cleared eagerly immediately after the transition.
 
 #ifdef VERIFY_HEAP
   if (FLAG_verify_heap) {
     RememberedSet<OLD_TO_NEW>::VerifyValidSlots(heap());
     RememberedSet<OLD_TO_OLD>::VerifyValidSlots(heap());
   }
 #endif
 }
 
-
 void MarkCompactCollector::CollectGarbage() {
   // Make sure that Prepare() has been called. The individual steps below will
   // update the state as they proceed.
   DCHECK(state_ == PREPARE_GC);
 
   MarkLiveObjects();
 
   DCHECK(heap_->incremental_marking()->IsStopped());
 
   ClearNonLiveReferences();
@@ skipping 955 matching lines @@
     // Visit the fields of the RegExp, including the updated FixedArray.
     VisitJSRegExp(map, object);
   }
 };
 
 
 void MarkCompactMarkingVisitor::Initialize() {
   StaticMarkingVisitor<MarkCompactMarkingVisitor>::Initialize();
 
   table_.Register(kVisitJSRegExp, &VisitRegExpAndFlushCode);
-
-  if (FLAG_track_gc_object_stats) {
-    MarkCompactObjectStatsVisitor::Initialize(&table_);
-  }
 }
 
 
 class CodeMarkingVisitor : public ThreadVisitor {
  public:
   explicit CodeMarkingVisitor(MarkCompactCollector* collector)
       : collector_(collector) {}
 
   void VisitThread(Isolate* isolate, ThreadLocalTop* top) {
     collector_->PrepareThreadForCodeFlushing(isolate, top);
@@ skipping 956 matching lines @@
 }
 
 void MarkCompactCollector::RegisterExternallyReferencedObject(Object** object) {
   DCHECK(in_use());
   HeapObject* heap_object = HeapObject::cast(*object);
   DCHECK(heap_->Contains(heap_object));
   MarkBit mark_bit = Marking::MarkBitFrom(heap_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;
   if (FLAG_print_cumulative_gc_stat) {
     start_time = heap_->MonotonicallyIncreasingTimeInMs();
   }
   // The recursive GC marker detects when it is nearing stack overflow,
   // and switches to a different marking system.  JS interrupts interfere
   // with the C stack limit check.
   PostponeInterruptsScope postpone(isolate());
 
   {
     TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_FINISH_INCREMENTAL);
     IncrementalMarking* incremental_marking = heap_->incremental_marking();
     if (was_marked_incrementally_) {
       incremental_marking->Finalize();
     } 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);
       }
     }
   }
 
 #ifdef DEBUG
   DCHECK(state_ == PREPARE_GC);
   state_ = MARK_LIVE_OBJECTS;
 #endif
@@ skipping 62 matching lines @@
       }
     }
   }
 
   if (FLAG_print_cumulative_gc_stat) {
     heap_->tracer()->AddMarkingTime(heap_->MonotonicallyIncreasingTimeInMs() -
                                     start_time);
   }
   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();
   }
 }
 
 
 void MarkCompactCollector::ClearNonLiveReferences() {
   TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_CLEAR);
 
   {
@@ skipping 1685 matching lines @@
       // The target is always in old space, we don't have to record the slot in
       // the old-to-new remembered set.
       DCHECK(!heap()->InNewSpace(target));
       RecordRelocSlot(host, &rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8