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