110 lines
4.6 KiB
C
110 lines
4.6 KiB
C
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// Copyright 2016 The Chromium Authors. All rights reserved.
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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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// PersistentSampleMap implements HistogramSamples interface. It is used
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// by the SparseHistogram class to store samples in persistent memory which
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// allows it to be shared between processes or live across restarts.
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#ifndef BASE_METRICS_PERSISTENT_SAMPLE_MAP_H_
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#define BASE_METRICS_PERSISTENT_SAMPLE_MAP_H_
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#include <stdint.h>
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#include <map>
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#include <memory>
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#include "base/compiler_specific.h"
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#include "base/macros.h"
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#include "base/metrics/histogram_base.h"
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#include "base/metrics/histogram_samples.h"
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#include "base/metrics/persistent_memory_allocator.h"
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namespace base {
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class PersistentHistogramAllocator;
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class PersistentSampleMapRecords;
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// The logic here is similar to that of SampleMap but with different data
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// structures. Changes here likely need to be duplicated there.
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class BASE_EXPORT PersistentSampleMap : public HistogramSamples {
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public:
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// Constructs a persistent sample map using a PersistentHistogramAllocator
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// as the data source for persistent records.
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PersistentSampleMap(uint64_t id,
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PersistentHistogramAllocator* allocator,
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Metadata* meta);
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~PersistentSampleMap() override;
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// HistogramSamples:
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void Accumulate(HistogramBase::Sample value,
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HistogramBase::Count count) override;
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HistogramBase::Count GetCount(HistogramBase::Sample value) const override;
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HistogramBase::Count TotalCount() const override;
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std::unique_ptr<SampleCountIterator> Iterator() const override;
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// Uses a persistent-memory |iterator| to locate and return information about
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// the next record holding information for a PersistentSampleMap. The record
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// could be for any Map so return the |sample_map_id| as well.
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static PersistentMemoryAllocator::Reference GetNextPersistentRecord(
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PersistentMemoryAllocator::Iterator& iterator,
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uint64_t* sample_map_id);
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// Creates a new record in an |allocator| storing count information for a
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// specific sample |value| of a histogram with the given |sample_map_id|.
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static PersistentMemoryAllocator::Reference CreatePersistentRecord(
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PersistentMemoryAllocator* allocator,
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uint64_t sample_map_id,
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HistogramBase::Sample value);
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protected:
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// Performs arithemetic. |op| is ADD or SUBTRACT.
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bool AddSubtractImpl(SampleCountIterator* iter, Operator op) override;
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// Gets a pointer to a "count" corresponding to a given |value|. Returns NULL
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// if sample does not exist.
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HistogramBase::Count* GetSampleCountStorage(HistogramBase::Sample value);
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// Gets a pointer to a "count" corresponding to a given |value|, creating
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// the sample (initialized to zero) if it does not already exists.
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HistogramBase::Count* GetOrCreateSampleCountStorage(
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HistogramBase::Sample value);
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private:
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// Gets the object that manages persistent records. This returns the
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// |records_| member after first initializing it if necessary.
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PersistentSampleMapRecords* GetRecords();
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// Imports samples from persistent memory by iterating over all sample
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// records found therein, adding them to the sample_counts_ map. If a
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// count for the sample |until_value| is found, stop the import and return
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// a pointer to that counter. If that value is not found, null will be
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// returned after all currently available samples have been loaded. Pass
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// true for |import_everything| to force the importing of all available
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// samples even if a match is found.
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HistogramBase::Count* ImportSamples(HistogramBase::Sample until_value,
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bool import_everything);
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// All created/loaded sample values and their associated counts. The storage
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// for the actual Count numbers is owned by the |records_| object and its
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// underlying allocator.
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std::map<HistogramBase::Sample, HistogramBase::Count*> sample_counts_;
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// The allocator that manages histograms inside persistent memory. This is
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// owned externally and is expected to live beyond the life of this object.
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PersistentHistogramAllocator* allocator_;
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// The object that manages sample records inside persistent memory. This is
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// owned by the |allocator_| object (above) and so, like it, is expected to
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// live beyond the life of this object. This value is lazily-initialized on
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// first use via the GetRecords() accessor method.
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PersistentSampleMapRecords* records_ = nullptr;
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DISALLOW_COPY_AND_ASSIGN(PersistentSampleMap);
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};
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} // namespace base
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#endif // BASE_METRICS_PERSISTENT_SAMPLE_MAP_H_
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