[NOT FOR LANDING] Patch for experiments: V8

src/heap/incremental-marking.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/incremental-marking.h"
 
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
 #include "src/conversions.h"
 #include "src/heap/gc-idle-time-handler.h"
@@ skipping 718 matching lines @@
       heap_->mark_compact_collector()->marking_deque()->top();
 
   // After finishing incremental marking, we try to discover all unmarked
   // objects to reduce the marking load in the final pause.
   // 1) We scan and mark the roots again to find all changes to the root set.
   // 2) We mark the object groups.
   // 3) Age and retain maps embedded in optimized code.
   // 4) Remove weak cell with live values from the list of weak cells, they
   // do not need processing during GC.
   MarkRoots();
-  if (!heap_->local_embedder_heap_tracer()->InUse()) {
+  if (!heap_->local_embedder_heap_tracer()->InUse() &&
+      FLAG_object_grouping_in_incremental_finalization) {
     MarkObjectGroups();
   }
-  if (incremental_marking_finalization_rounds_ == 0) {

[ulan, 2017/03/30 16:24:30]

This changes reduce noise in incremental finalization step.

-    // Map retaining is needed for perfromance, not correctness,
-    // so we can do it only once at the beginning of the finalization.
-    RetainMaps();
-  }
-  ProcessWeakCells();
 
   int marking_progress =
       abs(old_marking_deque_top -
           heap_->mark_compact_collector()->marking_deque()->top());
 
   marking_progress += static_cast<int>(
       heap_->local_embedder_heap_tracer()->NumberOfCachedWrappersToTrace());
 
   double end = heap_->MonotonicallyIncreasingTimeInMs();
   double delta = end - start;
@@ skipping 454 matching lines @@
   idle_marking_delay_counter_++;
 }
 
 
 void IncrementalMarking::ClearIdleMarkingDelayCounter() {
   idle_marking_delay_counter_ = 0;
 }
 
 }  // namespace internal
 }  // namespace v8