histogram_snapshot_manager.cc revision 2a99a7e74a7f215066514fe81d2bfa6639d9eddd 
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
13using std::map;
14using std::string;
15
16namespace base {
17
18HistogramSnapshotManager::HistogramSnapshotManager(
19    HistogramFlattener* histogram_flattener)
20    : histogram_flattener_(histogram_flattener) {
21  DCHECK(histogram_flattener_);
22}
23
24HistogramSnapshotManager::~HistogramSnapshotManager() {
25  STLDeleteValues(&logged_samples_);
26}
27
28void 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
43void 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
101void 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
118