[Experimental, DO NOT LAND] bucket num 16

base/trace_event/heap_profiler_allocation_register.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/trace_event/heap_profiler_allocation_register.h"
 
 #include <algorithm>
 
 #include "base/trace_event/trace_event_memory_overhead.h"
 
@@ skipping 37 matching lines @@
   }
 
   total_value += backtrace.frame_count;
 
   // These magic constants give best results in terms of average collisions
   // per backtrace. They were found by replaying real backtraces from Linux
   // and Android against different hash functions.
   return (total_value * 131101) >> 14;
 }
 
-size_t AllocationRegister::AddressHasher::operator () (
-    const void* address) const {
-  // The multiplicative hashing scheme from [Knuth 1998]. The value of |a| has
-  // been chosen carefully based on measurements with real-word data (addresses
-  // recorded from a Chrome trace run). It is the first prime after 2^17. For
-  // |shift|, 15 yield good results for both 2^18 and 2^19 bucket sizes.
-  // Microbenchmarks show that this simple scheme outperforms fancy hashes like
-  // Murmur3 by 20 to 40 percent.
-  const uintptr_t key = reinterpret_cast<uintptr_t>(address);
-  const uintptr_t a = 131101;
-  const uintptr_t shift = 15;
-  const uintptr_t h = (key * a) >> shift;
-  return h;
-}
-
 AllocationRegister::AllocationRegister()
     : AllocationRegister(kAllocationCapacity, kBacktraceCapacity) {}
 
 AllocationRegister::AllocationRegister(size_t allocation_capacity,
                                        size_t backtrace_capacity)
     : allocations_(allocation_capacity),
       backtraces_(backtrace_capacity) {}
 
 AllocationRegister::~AllocationRegister() {
 }
@@ skipping 88 matching lines @@
       address_and_info.first,
       address_and_info.second.size,
       AllocationContext(
           backtrace_and_count.first,
           address_and_info.second.type_name)
   };
 }
 
 }  // namespace trace_event
 }  // namespace base