100 lines
4.2 KiB
C++
100 lines
4.2 KiB
C++
// Copyright 2012 The Chromium Authors
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_METRICS_HISTOGRAM_SNAPSHOT_MANAGER_H_
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#define BASE_METRICS_HISTOGRAM_SNAPSHOT_MANAGER_H_
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#include <stdint.h>
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#include <atomic>
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#include <map>
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#include <memory>
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#include <vector>
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#include "base/base_export.h"
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#include "base/gtest_prod_util.h"
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#include "base/memory/raw_ptr.h"
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#include "base/metrics/histogram_base.h"
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namespace base {
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class HistogramSamples;
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class HistogramFlattener;
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// HistogramSnapshotManager handles the logistics of gathering up available
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// histograms for recording either to disk or for transmission (such as from
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// renderer to browser, or from browser to UMA upload). Since histograms can sit
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// in memory for an extended period of time, and are vulnerable to memory
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// corruption, this class also validates as much redundancy as it can before
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// calling for the marginal change (a.k.a., delta) in a histogram to be
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// recorded.
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class BASE_EXPORT HistogramSnapshotManager final {
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public:
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explicit HistogramSnapshotManager(HistogramFlattener* histogram_flattener);
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HistogramSnapshotManager(const HistogramSnapshotManager&) = delete;
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HistogramSnapshotManager& operator=(const HistogramSnapshotManager&) = delete;
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~HistogramSnapshotManager();
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// Snapshots all histograms and asks |histogram_flattener_| to record the
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// delta. |flags_to_set| is used to set flags for each histogram.
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// |required_flags| is used to select which histograms to record. Only
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// histograms with all of the required flags are selected. If all histograms
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// should be recorded, use |Histogram::kNoFlags| as the required flag.
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void PrepareDeltas(const std::vector<HistogramBase*>& histograms,
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HistogramBase::Flags flags_to_set,
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HistogramBase::Flags required_flags);
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// Same as PrepareDeltas() above, but the samples obtained from the histograms
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// are not immediately marked as logged. Instead, they are stored internally
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// in |histograms_and_snapshots_|, and a call to MarkUnloggedSamplesAsLogged()
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// should be made subsequently in order to mark them as logged.
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void SnapshotUnloggedSamples(const std::vector<HistogramBase*>& histograms,
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HistogramBase::Flags required_flags);
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// Marks the unlogged samples obtained from SnapshotUnloggedSamples() as
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// logged. For each call to this function, there should be a corresponding
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// call to SnapshotUnloggedSamples() before it.
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void MarkUnloggedSamplesAsLogged();
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// When the collection is not so simple as can be done using a single
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// iterator, the steps can be performed separately. Call PerpareDelta()
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// as many times as necessary. PrepareFinalDelta() works like PrepareDelta()
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// except that it does not update the previous logged values and can thus
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// be used with read-only files.
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void PrepareDelta(HistogramBase* histogram);
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void PrepareFinalDelta(const HistogramBase* histogram);
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private:
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FRIEND_TEST_ALL_PREFIXES(HistogramSnapshotManagerTest, CheckMerge);
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using HistogramSnapshotPair =
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std::pair<HistogramBase*, std::unique_ptr<HistogramSamples>>;
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// Capture and hold samples from a histogram. This does all the heavy
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// lifting for PrepareDelta() and PrepareFinalDelta().
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void PrepareSamples(const HistogramBase* histogram,
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const HistogramSamples& samples);
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// A list of histograms and snapshots of unlogged samples. Filled when calling
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// SnapshotUnloggedSamples(). They are marked as logged when calling
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// MarkUnloggedSamplesAsLogged().
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std::vector<HistogramSnapshotPair> histograms_and_snapshots_;
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// Keeps track of whether SnapshotUnloggedSamples() has been called. This
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// resets back to false after calling MarkUnloggedSamplesAsLogged(), so that
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// the same HistogramSnapshotManager instance can be used to take multiple
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// snapshots if needed.
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bool unlogged_samples_snapshot_taken_ = false;
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// |histogram_flattener_| handles the logistics of recording the histogram
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// deltas.
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const raw_ptr<HistogramFlattener> histogram_flattener_; // Weak.
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};
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} // namespace base
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#endif // BASE_METRICS_HISTOGRAM_SNAPSHOT_MANAGER_H_
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