base/metrics/histogram_snapshot_manager.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/metrics/histogram_snapshot_manager.h"
   6
   7 #include "base/memory/scoped_ptr.h"
   8 #include "base/metrics/histogram_flattener.h"
   9 #include "base/metrics/histogram_samples.h"
  10 #include "base/metrics/statistics_recorder.h"
  11 #include "base/stl_util.h"
  12
  13 using std::map;
  14 using std::string;
  15
  16 namespace base {
  17
  18 HistogramSnapshotManager::HistogramSnapshotManager(
  19     HistogramFlattener* histogram_flattener)
  20     : histogram_flattener_(histogram_flattener) {
  21   DCHECK(histogram_flattener_);
  22 }
  23
  24 HistogramSnapshotManager::~HistogramSnapshotManager() {
  25   STLDeleteValues(&logged_samples_);
  26 }
  27
  28 void HistogramSnapshotManager::PrepareDeltas(
  29     HistogramBase::Flags flag_to_set,
  30     HistogramBase::Flags required_flags) {
  31   StatisticsRecorder::Histograms histograms;
  32   StatisticsRecorder::GetHistograms(&histograms);
  33   for (StatisticsRecorder::Histograms::const_iterator it = histograms.begin();
  34        histograms.end() != it;
  35        ++it) {
  36     (*it)->SetFlags(flag_to_set);
  37     if (((*it)->flags() & required_flags) == required_flags)
  38       PrepareDelta(**it);
  39   }
  40 }
  41
  42 void HistogramSnapshotManager::PrepareDelta(const HistogramBase& histogram) {
  43   DCHECK(histogram_flattener_);
  44
  45   // Get up-to-date snapshot of sample stats.
  46   scoped_ptr<HistogramSamples> snapshot(histogram.SnapshotSamples());
  47   const std::string& histogram_name = histogram.histogram_name();
  48
  49   int corruption = histogram.FindCorruption(*snapshot);
  50
  51   // Crash if we detect that our histograms have been overwritten.  This may be
  52   // a fair distance from the memory smasher, but we hope to correlate these
  53   // crashes with other events, such as plugins, or usage patterns, etc.
  54   if (HistogramBase::BUCKET_ORDER_ERROR & corruption) {
  55     // The checksum should have caught this, so crash separately if it didn't.
  56     CHECK_NE(0, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
  57     CHECK(false);  // Crash for the bucket order corruption.
  58   }
  59   // Checksum corruption might not have caused order corruption.
  60   CHECK_EQ(0, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
  61
  62   // Note, at this point corruption can only be COUNT_HIGH_ERROR or
  63   // COUNT_LOW_ERROR and they never arise together, so we don't need to extract
  64   // bits from corruption.
  65   if (corruption) {
  66     DLOG(ERROR) << "Histogram: " << histogram_name
  67                 << " has data corruption: " << corruption;
  68     histogram_flattener_->InconsistencyDetected(
  69         static_cast<HistogramBase::Inconsistency>(corruption));
  70     // Don't record corrupt data to metrics services.
  71     int old_corruption = inconsistencies_[histogram_name];
  72     if (old_corruption == (corruption | old_corruption))
  73       return;  // We've already seen this corruption for this histogram.
  74     inconsistencies_[histogram_name] |= corruption;
  75     histogram_flattener_->UniqueInconsistencyDetected(
  76         static_cast<HistogramBase::Inconsistency>(corruption));
  77     return;
  78   }
  79
  80   HistogramSamples* to_log;
  81   map<string, HistogramSamples*>::iterator it =
  82       logged_samples_.find(histogram_name);
  83   if (it == logged_samples_.end()) {
  84     to_log = snapshot.release();
  85
  86     // This histogram has not been logged before, add a new entry.
  87     logged_samples_[histogram_name] = to_log;
  88   } else {
  89     HistogramSamples* already_logged = it->second;
  90     InspectLoggedSamplesInconsistency(*snapshot, already_logged);
  91     snapshot->Subtract(*already_logged);
  92     already_logged->Add(*snapshot);
  93     to_log = snapshot.get();
  94   }
  95
  96   if (to_log->TotalCount() > 0)
  97     histogram_flattener_->RecordDelta(histogram, *to_log);
  98 }
  99
 100 void HistogramSnapshotManager::InspectLoggedSamplesInconsistency(
 101       const HistogramSamples& new_snapshot,
 102       HistogramSamples* logged_samples) {
 103   HistogramBase::Count discrepancy =
 104       logged_samples->TotalCount() - logged_samples->redundant_count();
 105   if (!discrepancy)
 106     return;
 107
 108   histogram_flattener_->InconsistencyDetectedInLoggedCount(discrepancy);
 109   if (discrepancy > Histogram::kCommonRaceBasedCountMismatch) {
 110     // Fix logged_samples.
 111     logged_samples->Subtract(*logged_samples);
 112     logged_samples->Add(new_snapshot);
 113   }
 114 }
 115
 116 }  // namespace base