Introduce a flag to change the new space growth factor

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 1295 matching lines @@
 }
 
 
 void NewSpace::Flip() { SemiSpace::Swap(&from_space_, &to_space_); }
 
 
 void NewSpace::Grow() {
   // Double the semispace size but only up to maximum capacity.
   DCHECK(TotalCapacity() < MaximumCapacity());
   int new_capacity =
-      Min(MaximumCapacity(), 2 * static_cast<int>(TotalCapacity()));
+      Min(MaximumCapacity(),
+          FLAG_semi_space_growth_factor * static_cast<int>(TotalCapacity()));
   if (to_space_.GrowTo(new_capacity)) {
     // Only grow from space if we managed to grow to-space.
     if (!from_space_.GrowTo(new_capacity)) {
       // If we managed to grow to-space but couldn't grow from-space,
       // attempt to shrink to-space.
       if (!to_space_.ShrinkTo(from_space_.TotalCapacity())) {
         // We are in an inconsistent state because we could not
         // commit/uncommit memory from new space.
         CHECK(false);
       }
@@ skipping 1877 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 }
 }  // namespace v8::internal