Improve efficiency of persistent sparse histograms.

base/metrics/sparse_histogram.cc

 // Copyright (c) 2012 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/metrics/sparse_histogram.h"
 
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "base/metrics/metrics_hashes.h"
@@ skipping 56 matching lines @@
   } else {
     ReportHistogramActivity(*histogram, HISTOGRAM_LOOKUP);
   }
 
   DCHECK_EQ(SPARSE_HISTOGRAM, histogram->GetHistogramType());
   return histogram;
 }
 
 // static
 std::unique_ptr<HistogramBase> SparseHistogram::PersistentCreate(
-    PersistentMemoryAllocator* allocator,
+    PersistentHistogramAllocator* allocator,
     const std::string& name,
     HistogramSamples::Metadata* meta,
     HistogramSamples::Metadata* logged_meta) {
   return WrapUnique(
       new SparseHistogram(allocator, name, meta, logged_meta));
 }
 
 SparseHistogram::~SparseHistogram() {}
 
 uint64_t SparseHistogram::name_hash() const {
@@ skipping 70 matching lines @@
 
 bool SparseHistogram::SerializeInfoImpl(Pickle* pickle) const {
   return pickle->WriteString(histogram_name()) && pickle->WriteInt(flags());
 }
 
 SparseHistogram::SparseHistogram(const std::string& name)
     : HistogramBase(name),
       samples_(new SampleMap(HashMetricName(name))),
       logged_samples_(new SampleMap(samples_->id())) {}
 
-SparseHistogram::SparseHistogram(PersistentMemoryAllocator* allocator,
+SparseHistogram::SparseHistogram(PersistentHistogramAllocator* allocator,
                                  const std::string& name,
                                  HistogramSamples::Metadata* meta,
                                  HistogramSamples::Metadata* logged_meta)
     : HistogramBase(name),
       // While other histogram types maintain a static vector of values with
       // sufficient space for both "active" and "logged" samples, with each
       // SampleVector being given the appropriate half, sparse histograms
       // have no such initial allocation. Each sample has its own record
       // attached to a single PersistentSampleMap by a common 64-bit identifier.
       // Since a sparse histogram has two sample maps (active and logged),
@@ skipping 87 matching lines @@
                                        std::string* output) const {
   StringAppendF(output,
                 "Histogram: %s recorded %d samples",
                 histogram_name().c_str(),
                 total_count);
   if (flags() & ~kHexRangePrintingFlag)
     StringAppendF(output, " (flags = 0x%x)", flags() & ~kHexRangePrintingFlag);
 }
 
 }  // namespace base