Use just one to-space page for the promotion queue.

src/heap/heap.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/accessors.h"
 #include "src/api.h"
 #include "src/base/bits.h"
 #include "src/base/once.h"
@@ skipping 1439 matching lines @@
       DCHECK(start_of_current_page_ != store_buffer_->Top());
       store_buffer_->SetTop(start_of_current_page_);
     }
   } else {
     UNREACHABLE();
   }
 }
 
 
 void PromotionQueue::Initialize() {
-  // Assumes that a NewSpacePage exactly fits a number of promotion queue
-  // entries (where each is a pair of intptr_t). This allows us to simplify
-  // the test fpr when to switch pages.
+  // The last to-space page may be used for promotion queue. On promotion
+  // conflict, we use the emergency stack.
   DCHECK((Page::kPageSize - MemoryChunk::kBodyOffset) % (2 * kPointerSize) ==
          0);
-  limit_ = reinterpret_cast<intptr_t*>(heap_->new_space()->ToSpaceStart());
   front_ = rear_ =
       reinterpret_cast<intptr_t*>(heap_->new_space()->ToSpaceEnd());
+  limit_ = reinterpret_cast<intptr_t*>(
+      Page::FromAllocationTop(reinterpret_cast<Address>(rear_))->area_start());
   emergency_stack_ = NULL;
 }
 
 
 void PromotionQueue::RelocateQueueHead() {
   DCHECK(emergency_stack_ == NULL);
 
   Page* p = Page::FromAllocationTop(reinterpret_cast<Address>(rear_));
   intptr_t* head_start = rear_;
   intptr_t* head_end = Min(front_, reinterpret_cast<intptr_t*>(p->area_end()));
@@ skipping 5054 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   CODE_AGE_LIST_COMPLETE(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   MemCopy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 }
 }  // namespace v8::internal