Push memory reduction changes to 1.2 branch.

src/spaces.h

 // Copyright 2006-2008 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 414 matching lines @@
   static inline void UnprotectChunkFromPage(Page* page);
 #endif
 
 #ifdef DEBUG
   // Reports statistic info of the space.
   static void ReportStatistics();
 #endif
 
   // Due to encoding limitation, we can only have 8K chunks.
   static const int kMaxNofChunks = 1 << Page::kPageSizeBits;
-  // If a chunk has at least 32 pages, the maximum heap size is about
-  // 8 * 1024 * 32 * 8K = 2G bytes.
-  static const int kPagesPerChunk = 64;
+  // If a chunk has at least 16 pages, the maximum heap size is about
+  // 8k * 8K * 16 = 1G bytes.
+#ifdef V8_TARGET_ARCH_X64
+  static const int kPagesPerChunk = 32;
+#else
+  static const int kPagesPerChunk = 16;
+#endif
   static const int kChunkSize = kPagesPerChunk * Page::kPageSize;
 
  private:
   // Maximum space size in bytes.
   static int capacity_;
 
   // Allocated space size in bytes.
   static int size_;
 
   // The initial chunk of virtual memory.
@@ skipping 1344 matching lines @@
 
  private:
   LargeObjectChunk* current_;
   HeapObjectCallback size_func_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SPACES_H_