A very small marking bitmap (2 bits) is sufficient for large object page since just one object in i…

src/spaces.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 510 matching lines @@
       size_executable_ += reservation.size();
     }
 
 #ifdef DEBUG
     ZapBlock(base, CodePageGuardStartOffset());
     ZapBlock(base + CodePageAreaStartOffset(), body_size);
 #endif
     area_start = base + CodePageAreaStartOffset();
     area_end = area_start + body_size;
   } else {
-    chunk_size = MemoryChunk::kObjectStartOffset + body_size;
+    int object_start_offset = MemoryChunk::kObjectStartOffset;
+    if (owner != NULL && owner->identity() == LO_SPACE) {
+      object_start_offset = MemoryChunk::kLargeObjectStartOffset;
+    }
+
+    chunk_size = object_start_offset + body_size;
     base = AllocateAlignedMemory(chunk_size,
                                  MemoryChunk::kAlignment,
                                  executable,
                                  &reservation);
 
     if (base == NULL) return NULL;
 
 #ifdef DEBUG
     ZapBlock(base, chunk_size);
 #endif
 
-    area_start = base + Page::kObjectStartOffset;
+    area_start = base + object_start_offset;
     area_end = base + chunk_size;
   }
 
   isolate_->counters()->memory_allocated()->
       Increment(static_cast<int>(chunk_size));
 
   LOG(isolate_, NewEvent("MemoryChunk", base, chunk_size));
   if (owner != NULL) {
     ObjectSpace space = static_cast<ObjectSpace>(1 << owner->identity());
     PerformAllocationCallback(space, kAllocationActionAllocate, chunk_size);
@@ skipping 2298 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 
 } }  // namespace v8::internal