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
HistogramSnapshotManager(HistogramFlattener * histogram_flattener)15 HistogramSnapshotManager::HistogramSnapshotManager(
16 HistogramFlattener* histogram_flattener)
17 : histogram_flattener_(histogram_flattener) {
18 DCHECK(histogram_flattener_);
19 }
20
~HistogramSnapshotManager()21 HistogramSnapshotManager::~HistogramSnapshotManager() {
22 STLDeleteValues(&logged_samples_);
23 }
24
PrepareDeltas(HistogramBase::Flags flag_to_set,HistogramBase::Flags required_flags)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
PrepareDelta(const HistogramBase & histogram)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
45 // Crash if we detect that our histograms have been overwritten. This may be
46 // a fair distance from the memory smasher, but we hope to correlate these
47 // crashes with other events, such as plugins, or usage patterns, etc.
48 int corruption = histogram.FindCorruption(*snapshot);
49 if (HistogramBase::BUCKET_ORDER_ERROR & corruption) {
50 // The checksum should have caught this, so crash separately if it didn't.
51 CHECK_NE(0, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
52 CHECK(false); // Crash for the bucket order corruption.
53 }
54 // Checksum corruption might not have caused order corruption.
55 CHECK_EQ(0, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
56
57 // Note, at this point corruption can only be COUNT_HIGH_ERROR or
58 // COUNT_LOW_ERROR and they never arise together, so we don't need to extract
59 // bits from corruption.
60 const uint64_t histogram_hash = histogram.name_hash();
61 if (corruption) {
62 DLOG(ERROR) << "Histogram: " << histogram.histogram_name()
63 << " has data corruption: " << corruption;
64 histogram_flattener_->InconsistencyDetected(
65 static_cast<HistogramBase::Inconsistency>(corruption));
66 // Don't record corrupt data to metrics services.
67 int old_corruption = inconsistencies_[histogram_hash];
68 if (old_corruption == (corruption | old_corruption))
69 return; // We've already seen this corruption for this histogram.
70 inconsistencies_[histogram_hash] |= corruption;
71 histogram_flattener_->UniqueInconsistencyDetected(
72 static_cast<HistogramBase::Inconsistency>(corruption));
73 return;
74 }
75
76 HistogramSamples* to_log;
77 auto it = logged_samples_.find(histogram_hash);
78 if (it == logged_samples_.end()) {
79 to_log = snapshot.release();
80
81 // This histogram has not been logged before, add a new entry.
82 logged_samples_[histogram_hash] = to_log;
83 } else {
84 HistogramSamples* already_logged = it->second;
85 InspectLoggedSamplesInconsistency(*snapshot, already_logged);
86 snapshot->Subtract(*already_logged);
87 already_logged->Add(*snapshot);
88 to_log = snapshot.get();
89 }
90
91 if (to_log->TotalCount() > 0)
92 histogram_flattener_->RecordDelta(histogram, *to_log);
93 }
94
InspectLoggedSamplesInconsistency(const HistogramSamples & new_snapshot,HistogramSamples * logged_samples)95 void HistogramSnapshotManager::InspectLoggedSamplesInconsistency(
96 const HistogramSamples& new_snapshot,
97 HistogramSamples* logged_samples) {
98 HistogramBase::Count discrepancy =
99 logged_samples->TotalCount() - logged_samples->redundant_count();
100 if (!discrepancy)
101 return;
102
103 histogram_flattener_->InconsistencyDetectedInLoggedCount(discrepancy);
104 if (discrepancy > Histogram::kCommonRaceBasedCountMismatch) {
105 // Fix logged_samples.
106 logged_samples->Subtract(*logged_samples);
107 logged_samples->Add(new_snapshot);
108 }
109 }
110
111 } // namespace base
112