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