Reduce boot-up memory use of V8.

test/cctest/test-heap.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 
 #include <stdlib.h>
 
 #include "v8.h"
 
 #include "execution.h"
 #include "factory.h"
 #include "macro-assembler.h"
 #include "global-handles.h"
@@ skipping 1218 matching lines @@
   InitializeVM();
   HEAP->EnsureHeapIsIterable();
   intptr_t size_of_objects_1 = HEAP->SizeOfObjects();
   HeapIterator iterator;
   intptr_t size_of_objects_2 = 0;
   for (HeapObject* obj = iterator.next();
        obj != NULL;
        obj = iterator.next()) {
     size_of_objects_2 += obj->Size();
   }
-  // Delta must be within 5% of the larger result.
-  // TODO(gc): Tighten this up by distinguishing between byte
-  // arrays that are real and those that merely mark free space
-  // on the heap.
+  // Delta must be within 1% of the larger result.
   if (size_of_objects_1 > size_of_objects_2) {
     intptr_t delta = size_of_objects_1 - size_of_objects_2;
     PrintF("Heap::SizeOfObjects: %" V8_PTR_PREFIX "d, "
            "Iterator: %" V8_PTR_PREFIX "d, "
            "delta: %" V8_PTR_PREFIX "d\n",
            size_of_objects_1, size_of_objects_2, delta);
-    CHECK_GT(size_of_objects_1 / 20, delta);
+    CHECK_GT(size_of_objects_1 / 100, delta);
   } else {
     intptr_t delta = size_of_objects_2 - size_of_objects_1;
     PrintF("Heap::SizeOfObjects: %" V8_PTR_PREFIX "d, "
            "Iterator: %" V8_PTR_PREFIX "d, "
            "delta: %" V8_PTR_PREFIX "d\n",
            size_of_objects_1, size_of_objects_2, delta);
     CHECK_GT(size_of_objects_2 / 20, delta);
   }
 }
 
@@ skipping 359 matching lines @@
   // clearing correctly records slots in prototype transition array.
   i::FLAG_always_compact = true;
   Handle<Map> map(baseObject->map());
   CHECK(!space->LastPage()->Contains(map->prototype_transitions()->address()));
   CHECK(space->LastPage()->Contains(prototype->address()));
   baseObject->SetPrototype(*prototype, false)->ToObjectChecked();
   CHECK(map->GetPrototypeTransition(*prototype)->IsMap());
   HEAP->CollectAllGarbage(Heap::kNoGCFlags);
   CHECK(map->GetPrototypeTransition(*prototype)->IsMap());
 }