Add timeline event for weak handle processing.

runtime/vm/scavenger.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/scavenger.h"
 
 #include "vm/dart.h"
 #include "vm/dart_api_state.h"
 #include "vm/isolate.h"
 #include "vm/lockers.h"
 #include "vm/object.h"
 #include "vm/object_id_ring.h"
 #include "vm/safepoint.h"
 #include "vm/stack_frame.h"
 #include "vm/store_buffer.h"
 #include "vm/thread_registry.h"
+#include "vm/timeline.h"
 #include "vm/verified_memory.h"
 #include "vm/verifier.h"
 #include "vm/visitor.h"
 #include "vm/weak_table.h"
 
 namespace dart {
 
 DEFINE_FLAG(int, early_tenuring_threshold, 66,
             "When more than this percentage of promotion candidates survive, "
             "promote all survivors of next scavenge.");
@@ skipping 768 matching lines @@
   }
 
   // Prepare for a scavenge.
   SpaceUsage usage_before = GetCurrentUsage();
   intptr_t promo_candidate_words =
       (survivor_end_ - FirstObjectStart()) / kWordSize;
   SemiSpace* from = Prologue(isolate, invoke_api_callbacks);
   // The API prologue/epilogue may create/destroy zones, so we must not
   // depend on zone allocations surviving beyond the epilogue callback.
   {
-    StackZone zone(Thread::Current());
+    Thread* thread = Thread::Current();

[siva, 2016/05/25 17:39:12]

There is a Thread::Current() above in SafepointOperationScope maybe we should
hoist this above that and use thread over there too.

[rmacnak, 2016/05/25 17:53:26]

Hoisted.

+    StackZone zone(thread);
     // Setup the visitor and run the scavenge.
     ScavengerVisitor visitor(isolate, this, from);
     page_space->AcquireDataLock();
     IterateRoots(isolate, &visitor);
     int64_t start = OS::GetCurrentTimeMicros();
     ProcessToSpace(&visitor);
     int64_t middle = OS::GetCurrentTimeMicros();
-    ScavengerWeakVisitor weak_visitor(this);
-    IterateWeakRoots(isolate, &weak_visitor);
+    {
+      TIMELINE_FUNCTION_GC_DURATION(thread, "WeakHandleProcessing");
+      ScavengerWeakVisitor weak_visitor(this);
+      IterateWeakRoots(isolate, &weak_visitor);
+    }
     ProcessWeakReferences();
     page_space->ReleaseDataLock();
 
     // Scavenge finished. Run accounting.
     int64_t end = OS::GetCurrentTimeMicros();
     heap_->RecordTime(kProcessToSpace, middle - start);
     heap_->RecordTime(kIterateWeaks, end - middle);
     stats_history_.Add(
         ScavengeStats(start, end,
                       usage_before, GetCurrentUsage(),
@@ skipping 56 matching lines @@
 }
 
 
 void Scavenger::FreeExternal(intptr_t size) {
   ASSERT(size >= 0);
   external_size_ -= size;
   ASSERT(external_size_ >= 0);
 }
 
 }  // namespace dart