Get rid of fastMallocGoodSize() and replace it with something generic.

Source/wtf/QuantizedAllocation.h

+/*
+ * Copyright (C) 2013 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
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef WTF_QuantizedAllocation_h
+#define WTF_QuantizedAllocation_h
+
+// DESCRIPTION
+// QuantizedAllocation::quantizedSize() rounds up the specific size such that:
+// 1) Granularity of allocation sizes is >1, and grows as a fraction of the
+// allocation size. This property can be used to limit bucket fragmentation
+// when sitting on top of a high-granularity allocator such as PartitionAlloc.
+// 2) The sizes are likely (but not guaranteed) to correspond to exact "bucket
+// sizes" of any underlying allocator that implements standard bucketing.
+// This currently includes tcmalloc, Windows LFH and PartitionAlloc.
+
+#include "wtf/WTFExport.h"
+#include <limits.h>
+
+namespace WTF {
+
+class WTF_EXPORT QuantizedAllocation {
+public:
+    // Allocations above 32k are rounded to 4k (which is typically the system
+    // page size).
+    static const size_t kMaxAllocation = 32768;
+    static const size_t kMaxRounding = 4096;
+
+    // This is the minimum granularity of allocation, currently 16 bytes.
+    static const size_t kMinRounding = 16;
+
+    // After 256 bytes, the granularity doubles, and proceeds to double again
+    // as the allocation size further doubles.
+    static const size_t kMinRoundingLimit = 256;
+    static const size_t kTableSize = kMaxAllocation / kMinRoundingLimit;
+
+    // Using "unsigned" is not a limitation because Chromium's max malloc() is
+    // 2GB even on 64-bit.
+    static const size_t kMaxUnquantizedAllocation = UINT_MAX - kMaxRounding;
+
+    static void init();
+
+    static size_t quantizedSize(size_t size)
+    {
+        size_t roundToLessOne;
+        if (UNLIKELY(size >= kMaxAllocation))
+            roundToLessOne = kMaxRounding - 1;
+        else
+            roundToLessOne = table[size / kMinRoundingLimit];
+        return (size + roundToLessOne) & ~roundToLessOne;
+    }
+
+private:
+    static unsigned short table[kTableSize];
+};
+
+} // namespace WTF
+
+#endif // WTF_QuantizedAllocation_h