Trace how long it takes to compute the weak closure during mark-compact

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/v8.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
@@ skipping 2204 matching lines @@
         }
       }
     }
   }
 
   RootMarkingVisitor root_visitor(heap());
   MarkRoots(&root_visitor);
 
   ProcessTopOptimizedFrame(&root_visitor);
 
-  // The objects reachable from the roots are marked, yet unreachable
-  // objects are unmarked.  Mark objects reachable due to host
-  // application specific logic or through Harmony weak maps.
-  ProcessEphemeralMarking(&root_visitor, false);
+  {
+    GCTracer::Scope gc_scope(heap()->tracer(), GCTracer::Scope::MC_WEAKCLOSURE);
 
-  // The objects reachable from the roots, weak maps or object groups
-  // are marked. Objects pointed to only by weak global handles cannot be
-  // immediately reclaimed. Instead, we have to mark them as pending and mark
-  // objects reachable from them.
-  //
-  // First we identify nonlive weak handles and mark them as pending
-  // destruction.
-  heap()->isolate()->global_handles()->IdentifyWeakHandles(
-      &IsUnmarkedHeapObject);
-  // Then we mark the objects.
-  heap()->isolate()->global_handles()->IterateWeakRoots(&root_visitor);
+    // The objects reachable from the roots are marked, yet unreachable
+    // objects are unmarked.  Mark objects reachable due to host
+    // application specific logic or through Harmony weak maps.
+    ProcessEphemeralMarking(&root_visitor, false);
 
-  // Repeat Harmony weak maps marking to mark unmarked objects reachable from
-  // the weak roots we just marked as pending destruction.
-  //
-  // We only process harmony collections, as all object groups have been fully
-  // processed and no weakly reachable node can discover new objects groups.
-  ProcessEphemeralMarking(&root_visitor, true);
+    // The objects reachable from the roots, weak maps or object groups
+    // are marked. Objects pointed to only by weak global handles cannot be
+    // immediately reclaimed. Instead, we have to mark them as pending and mark
+    // objects reachable from them.
+    //
+    // First we identify nonlive weak handles and mark them as pending
+    // destruction.
+    heap()->isolate()->global_handles()->IdentifyWeakHandles(
+        &IsUnmarkedHeapObject);
+    // Then we mark the objects.
+    heap()->isolate()->global_handles()->IterateWeakRoots(&root_visitor);
+
+    // Repeat Harmony weak maps marking to mark unmarked objects reachable from
+    // the weak roots we just marked as pending destruction.
+    //
+    // We only process harmony collections, as all object groups have been fully
+    // processed and no weakly reachable node can discover new objects groups.
+    ProcessEphemeralMarking(&root_visitor, true);
+  }
 
   AfterMarking();
 
   if (FLAG_print_cumulative_gc_stat) {
     heap_->tracer()->AddMarkingTime(base::OS::TimeCurrentMillis() - start_time);
   }
 }
 
 
 void MarkCompactCollector::AfterMarking() {
@@ skipping 2177 matching lines @@
   SlotsBuffer* buffer = *buffer_address;
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 }
 }  // namespace v8::internal