Make new space allocation throughput estimation more accurate.

src/heap/spaces.cc

 // Copyright 2011 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/bits.h"
 #include "src/base/platform/platform.h"
 #include "src/full-codegen.h"
 #include "src/heap/mark-compact.h"
@@ skipping 1552 matching lines @@
   initial_total_capacity_ = RoundDown(initial_capacity, Page::kPageSize);
   total_capacity_ = initial_capacity;
   target_capacity_ = RoundDown(target_capacity, Page::kPageSize);
   maximum_total_capacity_ = RoundDown(maximum_capacity, Page::kPageSize);
   maximum_committed_ = 0;
   committed_ = false;
   start_ = start;
   address_mask_ = ~(maximum_capacity - 1);
   object_mask_ = address_mask_ | kHeapObjectTagMask;
   object_expected_ = reinterpret_cast<uintptr_t>(start) | kHeapObjectTag;
-  age_mark_ = start_;
+  age_mark_ = start_ + NewSpacePage::kObjectStartOffset;
 }
 
 
 void SemiSpace::TearDown() {
   start_ = NULL;
   total_capacity_ = 0;
 }
 
 
 bool SemiSpace::Commit() {
@@ skipping 1543 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 }
 }  // namespace v8::internal