1 // Copyright 2016 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 // PersistentSampleMap implements HistogramSamples interface. It is used 6 // by the SparseHistogram class to store samples in persistent memory which 7 // allows it to be shared between processes or live across restarts. 8 9 #ifndef BASE_METRICS_PERSISTENT_SAMPLE_MAP_H_ 10 #define BASE_METRICS_PERSISTENT_SAMPLE_MAP_H_ 11 12 #include <stdint.h> 13 14 #include <map> 15 #include <memory> 16 17 #include "base/compiler_specific.h" 18 #include "base/macros.h" 19 #include "base/metrics/histogram_base.h" 20 #include "base/metrics/histogram_samples.h" 21 #include "base/metrics/persistent_memory_allocator.h" 22 23 namespace base { 24 25 class PersistentHistogramAllocator; 26 class PersistentSampleMapRecords; 27 class PersistentSparseHistogramDataManager; 28 29 // The logic here is similar to that of SampleMap but with different data 30 // structures. Changes here likely need to be duplicated there. 31 class BASE_EXPORT PersistentSampleMap : public HistogramSamples { 32 public: 33 // Constructs a persistent sample map using a PersistentHistogramAllocator 34 // as the data source for persistent records. 35 PersistentSampleMap(uint64_t id, 36 PersistentHistogramAllocator* allocator, 37 Metadata* meta); 38 39 ~PersistentSampleMap() override; 40 41 // HistogramSamples: 42 void Accumulate(HistogramBase::Sample value, 43 HistogramBase::Count count) override; 44 HistogramBase::Count GetCount(HistogramBase::Sample value) const override; 45 HistogramBase::Count TotalCount() const override; 46 std::unique_ptr<SampleCountIterator> Iterator() const override; 47 48 // Uses a persistent-memory |iterator| to locate and return information about 49 // the next record holding information for a PersistentSampleMap. The record 50 // could be for any Map so return the |sample_map_id| as well. 51 static PersistentMemoryAllocator::Reference GetNextPersistentRecord( 52 PersistentMemoryAllocator::Iterator& iterator, 53 uint64_t* sample_map_id); 54 55 // Creates a new record in an |allocator| storing count information for a 56 // specific sample |value| of a histogram with the given |sample_map_id|. 57 static PersistentMemoryAllocator::Reference CreatePersistentRecord( 58 PersistentMemoryAllocator* allocator, 59 uint64_t sample_map_id, 60 HistogramBase::Sample value); 61 62 protected: 63 // Performs arithemetic. |op| is ADD or SUBTRACT. 64 bool AddSubtractImpl(SampleCountIterator* iter, Operator op) override; 65 66 // Gets a pointer to a "count" corresponding to a given |value|. Returns NULL 67 // if sample does not exist. 68 HistogramBase::Count* GetSampleCountStorage(HistogramBase::Sample value); 69 70 // Gets a pointer to a "count" corresponding to a given |value|, creating 71 // the sample (initialized to zero) if it does not already exists. 72 HistogramBase::Count* GetOrCreateSampleCountStorage( 73 HistogramBase::Sample value); 74 75 private: 76 // Gets the object that manages persistent records. This returns the 77 // |records_| member after first initializing it if necessary. 78 PersistentSampleMapRecords* GetRecords(); 79 80 // Imports samples from persistent memory by iterating over all sample 81 // records found therein, adding them to the sample_counts_ map. If a 82 // count for the sample |until_value| is found, stop the import and return 83 // a pointer to that counter. If that value is not found, null will be 84 // returned after all currently available samples have been loaded. Pass 85 // true for |import_everything| to force the importing of all available 86 // samples even if a match is found. 87 HistogramBase::Count* ImportSamples(HistogramBase::Sample until_value, 88 bool import_everything); 89 90 // All created/loaded sample values and their associated counts. The storage 91 // for the actual Count numbers is owned by the |records_| object and its 92 // underlying allocator. 93 std::map<HistogramBase::Sample, HistogramBase::Count*> sample_counts_; 94 95 // The allocator that manages histograms inside persistent memory. This is 96 // owned externally and is expected to live beyond the life of this object. 97 PersistentHistogramAllocator* allocator_; 98 99 // The object that manages sample records inside persistent memory. This is 100 // owned by the |allocator_| object (above) and so, like it, is expected to 101 // live beyond the life of this object. This value is lazily-initialized on 102 // first use via the GetRecords() accessor method. 103 PersistentSampleMapRecords* records_ = nullptr; 104 105 DISALLOW_COPY_AND_ASSIGN(PersistentSampleMap); 106 }; 107 108 } // namespace base 109 110 #endif // BASE_METRICS_PERSISTENT_SAMPLE_MAP_H_ 111