Decrease the kHashbits to 12 effectively restoring the pre-r89459 size

third_party/tcmalloc/chromium/src/packed-cache-inl.h

 // Copyright (c) 2007, Google Inc.
 // 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
@@ skipping 121 matching lines @@
 // the cache is T.  See also the big comment at the top of the file.
 template <int kKeybits, typename T>
 class PackedCache {
  public:
   typedef uintptr_t K;
   typedef size_t V;
 #ifdef TCMALLOC_SMALL_BUT_SLOW
   // Decrease the size map cache if running in the small memory mode.
   static const int kHashbits = 12;
 #else
-  static const int kHashbits = 16;
+  // We don't want the hash map to occupy 512K memory at Chromium, so
+  // kHashbits is decreased from 16 to 12.

[jar (doing other things), 2011/06/20 16:45:02]

Question: Rather than forking this file, why don't we just work to set the
TCMALLOC_SMALL_SLOW flag (in Chromium), and get this without a file change?

+  static const int kHashbits = 12;
 #endif
   static const int kValuebits = 7;
   static const bool kUseWholeKeys = kKeybits + kValuebits <= 8 * sizeof(T);
 
   explicit PackedCache(V initial_value) {
     COMPILE_ASSERT(kKeybits <= sizeof(K) * 8, key_size);
     COMPILE_ASSERT(kValuebits <= sizeof(V) * 8, value_size);
     COMPILE_ASSERT(kHashbits <= kKeybits, hash_function);
     COMPILE_ASSERT(kKeybits - kHashbits + kValuebits <= kTbits,
                    entry_size_must_be_big_enough);
@@ skipping 76 matching lines @@
   static const V kValueMask = N_ONES_(V, kValuebits);
 
   // array_ is the cache.  Its elements are volatile because any
   // thread can write any array element at any time.
   volatile T array_[1 << kHashbits];
 };
 
 #undef N_ONES_
 
 #endif  // TCMALLOC_PACKED_CACHE_INL_H_