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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/metrics/histogram_snapshot_manager.h"
#include "base/memory/scoped_ptr.h"
#include "base/metrics/histogram_flattener.h"
#include "base/metrics/histogram_samples.h"
#include "base/metrics/statistics_recorder.h"
#include "base/stl_util.h"
using std::map;
using std::string;
namespace base {
HistogramSnapshotManager::HistogramSnapshotManager(
HistogramFlattener* histogram_flattener)
: histogram_flattener_(histogram_flattener) {
DCHECK(histogram_flattener_);
}
HistogramSnapshotManager::~HistogramSnapshotManager() {
STLDeleteValues(&logged_samples_);
}
void HistogramSnapshotManager::PrepareDeltas(
HistogramBase::Flags flag_to_set,
HistogramBase::Flags required_flags) {
StatisticsRecorder::Histograms histograms;
StatisticsRecorder::GetHistograms(&histograms);
for (StatisticsRecorder::Histograms::const_iterator it = histograms.begin();
histograms.end() != it;
++it) {
(*it)->SetFlags(flag_to_set);
if (((*it)->flags() & required_flags) == required_flags)
PrepareDelta(**it);
}
}
void HistogramSnapshotManager::PrepareDelta(const HistogramBase& histogram) {
DCHECK(histogram_flattener_);
// Get up-to-date snapshot of sample stats.
scoped_ptr<HistogramSamples> snapshot(histogram.SnapshotSamples());
const std::string& histogram_name = histogram.histogram_name();
int corruption = histogram.FindCorruption(*snapshot);
// Crash if we detect that our histograms have been overwritten. This may be
// a fair distance from the memory smasher, but we hope to correlate these
// crashes with other events, such as plugins, or usage patterns, etc.
if (HistogramBase::BUCKET_ORDER_ERROR & corruption) {
// The checksum should have caught this, so crash separately if it didn't.
CHECK_NE(0, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
CHECK(false); // Crash for the bucket order corruption.
}
// Checksum corruption might not have caused order corruption.
CHECK_EQ(0, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
// Note, at this point corruption can only be COUNT_HIGH_ERROR or
// COUNT_LOW_ERROR and they never arise together, so we don't need to extract
// bits from corruption.
if (corruption) {
DLOG(ERROR) << "Histogram: " << histogram_name
<< " has data corruption: " << corruption;
histogram_flattener_->InconsistencyDetected(
static_cast<HistogramBase::Inconsistency>(corruption));
// Don't record corrupt data to metrics services.
int old_corruption = inconsistencies_[histogram_name];
if (old_corruption == (corruption | old_corruption))
return; // We've already seen this corruption for this histogram.
inconsistencies_[histogram_name] |= corruption;
histogram_flattener_->UniqueInconsistencyDetected(
static_cast<HistogramBase::Inconsistency>(corruption));
return;
}
HistogramSamples* to_log;
map<string, HistogramSamples*>::iterator it =
logged_samples_.find(histogram_name);
if (it == logged_samples_.end()) {
to_log = snapshot.release();
// This histogram has not been logged before, add a new entry.
logged_samples_[histogram_name] = to_log;
} else {
HistogramSamples* already_logged = it->second;
InspectLoggedSamplesInconsistency(*snapshot, already_logged);
snapshot->Subtract(*already_logged);
already_logged->Add(*snapshot);
to_log = snapshot.get();
}
if (to_log->TotalCount() > 0)
histogram_flattener_->RecordDelta(histogram, *to_log);
}
void HistogramSnapshotManager::InspectLoggedSamplesInconsistency(
const HistogramSamples& new_snapshot,
HistogramSamples* logged_samples) {
HistogramBase::Count discrepancy =
logged_samples->TotalCount() - logged_samples->redundant_count();
if (!discrepancy)
return;
histogram_flattener_->InconsistencyDetectedInLoggedCount(discrepancy);
if (discrepancy > Histogram::kCommonRaceBasedCountMismatch) {
// Fix logged_samples.
logged_samples->Subtract(*logged_samples);
logged_samples->Add(new_snapshot);
}
}
} // namespace base
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