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| 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 #ifndef BASE_METRICS_HISTOGRAM_PERSISTENCE_H_ |
| 6 #define BASE_METRICS_HISTOGRAM_PERSISTENCE_H_ |
| 7 |
| 8 #include "base/atomicops.h" |
| 9 #include "base/base_export.h" |
| 10 #include "base/feature_list.h" |
| 11 #include "base/memory/scoped_ptr.h" |
| 12 #include "base/memory/shared_memory.h" |
| 13 #include "base/metrics/histogram_base.h" |
| 14 #include "base/metrics/persistent_memory_allocator.h" |
| 15 #include "base/strings/string_piece.h" |
| 16 |
| 17 namespace base { |
| 18 |
| 19 // Feature definition for enabling histogram persistence. |
| 20 BASE_EXPORT extern const Feature kPersistentHistogramsFeature; |
| 21 |
| 22 // This class manages histograms created within a PersistentMemoryAllocator. |
| 23 class BASE_EXPORT PersistentHistogramAllocator { |
| 24 public: |
| 25 // This iterator is used for fetching persistent histograms from an allocator. |
| 26 class Iterator { |
| 27 public: |
| 28 bool is_clear() { return memory_iter.is_clear(); } |
| 29 |
| 30 private: |
| 31 friend class PersistentHistogramAllocator; |
| 32 |
| 33 // The iterator used for stepping through persistent memory iterables. |
| 34 PersistentMemoryAllocator::Iterator memory_iter; |
| 35 }; |
| 36 |
| 37 using Reference = PersistentMemoryAllocator::Reference; |
| 38 |
| 39 // A PersistentHistogramAllocator is constructed from a PersistentMemory- |
| 40 // Allocator object of which it takes ownership. |
| 41 PersistentHistogramAllocator(scoped_ptr<PersistentMemoryAllocator> memory); |
| 42 ~PersistentHistogramAllocator(); |
| 43 |
| 44 // Direct access to underlying memory allocator. If the segment is shared |
| 45 // across threads or processes, reading data through these values does |
| 46 // not guarantee consistency. Use with care. Do not write. |
| 47 PersistentMemoryAllocator* memory_allocator() { |
| 48 return memory_allocator_.get(); |
| 49 } |
| 50 |
| 51 // Implement the "metadata" API of a PersistentMemoryAllocator, forwarding |
| 52 // those requests to the real one. |
| 53 uint64_t Id() const { return memory_allocator_->Id(); } |
| 54 const char* Name() const { return memory_allocator_->Name(); } |
| 55 const void* data() const { return memory_allocator_->data(); } |
| 56 size_t length() const { return memory_allocator_->length(); } |
| 57 size_t used() const { return memory_allocator_->used(); } |
| 58 |
| 59 // Recreate a Histogram from data held in persistent memory. Though this |
| 60 // object will be local to the current process, the sample data will be |
| 61 // shared with all other threads referencing it. This method takes a |ref| |
| 62 // to where the top-level histogram data may be found in this allocator. |
| 63 // This method will return null if any problem is detected with the data. |
| 64 scoped_ptr<HistogramBase> GetHistogram(Reference ref); |
| 65 |
| 66 // Get the next histogram in persistent data based on iterator. |
| 67 scoped_ptr<HistogramBase> GetNextHistogram(Iterator* iter) { |
| 68 return GetNextHistogramWithIgnore(iter, 0); |
| 69 } |
| 70 |
| 71 // Create an iterator for going through all histograms in an allocator. |
| 72 void CreateIterator(Iterator* iter); |
| 73 |
| 74 // Allocate a new persistent histogram. The returned histogram will not |
| 75 // be able to be located by other allocators until it is "finalized". |
| 76 scoped_ptr<HistogramBase> AllocateHistogram( |
| 77 HistogramType histogram_type, |
| 78 const std::string& name, |
| 79 int minimum, |
| 80 int maximum, |
| 81 const BucketRanges* bucket_ranges, |
| 82 int32_t flags, |
| 83 Reference* ref_ptr); |
| 84 |
| 85 // Finalize the creation of the histogram, making it available to other |
| 86 // processes if |registered| (as in: added to the StatisticsRecorder) is |
| 87 // True, forgetting it otherwise. |
| 88 void FinalizeHistogram(Reference ref, bool registered); |
| 89 |
| 90 // Create internal histograms for tracking memory use and allocation sizes |
| 91 // for allocator of |name| (which can simply be the result of Name()). This |
| 92 // is done seperately from construction for situations such as when the |
| 93 // histograms will be backed by memory provided by this very allocator. |
| 94 // |
| 95 // IMPORTANT: Callers must update tools/metrics/histograms/histograms.xml |
| 96 // with the following histograms: |
| 97 // UMA.PersistentAllocator.name.Allocs |
| 98 // UMA.PersistentAllocator.name.UsedPct |
| 99 void CreateTrackingHistograms(StringPiece name); |
| 100 void UpdateTrackingHistograms(); |
| 101 |
| 102 // Manage a PersistentHistogramAllocator for globally storing histograms in |
| 103 // a space that can be persisted or shared between processes. There is only |
| 104 // ever one allocator for all such histograms created by a single process. |
| 105 // This takes ownership of the object and should be called as soon as |
| 106 // possible during startup to capture as many histograms as possible and |
| 107 // while operating single-threaded so there are no race-conditions. |
| 108 static void SetGlobalAllocator( |
| 109 scoped_ptr<PersistentHistogramAllocator> allocator); |
| 110 static PersistentHistogramAllocator* GetGlobalAllocator(); |
| 111 |
| 112 // This access to the persistent allocator is only for testing; it extracts |
| 113 // the current allocator completely. This allows easy creation of histograms |
| 114 // within persistent memory segments which can then be extracted and used |
| 115 // in other ways. |
| 116 static scoped_ptr<PersistentHistogramAllocator> |
| 117 ReleaseGlobalAllocatorForTesting(); |
| 118 |
| 119 // These helper methods perform SetGlobalAllocator() calls with allocators |
| 120 // of the specified type and parameters. |
| 121 static void CreateGlobalAllocatorOnPersistentMemory( |
| 122 void* base, |
| 123 size_t size, |
| 124 size_t page_size, |
| 125 uint64_t id, |
| 126 StringPiece name); |
| 127 static void CreateGlobalAllocatorOnLocalMemory( |
| 128 size_t size, |
| 129 uint64_t id, |
| 130 StringPiece name); |
| 131 static void CreateGlobalAllocatorOnSharedMemory( |
| 132 size_t size, |
| 133 const SharedMemoryHandle& handle); |
| 134 |
| 135 // Import new histograms from the global PersistentHistogramAllocator. It's |
| 136 // possible for other processes to create histograms in the active memory |
| 137 // segment; this adds those to the internal list of known histograms to |
| 138 // avoid creating duplicates that would have to be merged during reporting. |
| 139 // Every call to this method resumes from the last entry it saw; it costs |
| 140 // nothing if nothing new has been added. |
| 141 static void ImportGlobalHistograms(); |
| 142 |
| 143 // Histogram containing creation results. Visible for testing. |
| 144 static HistogramBase* GetCreateHistogramResultHistogram(); |
| 145 |
| 146 private: |
| 147 // Enumerate possible creation results for reporting. |
| 148 enum CreateHistogramResultType { |
| 149 // Everything was fine. |
| 150 CREATE_HISTOGRAM_SUCCESS = 0, |
| 151 |
| 152 // Pointer to metadata was not valid. |
| 153 CREATE_HISTOGRAM_INVALID_METADATA_POINTER, |
| 154 |
| 155 // Histogram metadata was not valid. |
| 156 CREATE_HISTOGRAM_INVALID_METADATA, |
| 157 |
| 158 // Ranges information was not valid. |
| 159 CREATE_HISTOGRAM_INVALID_RANGES_ARRAY, |
| 160 |
| 161 // Counts information was not valid. |
| 162 CREATE_HISTOGRAM_INVALID_COUNTS_ARRAY, |
| 163 |
| 164 // Could not allocate histogram memory due to corruption. |
| 165 CREATE_HISTOGRAM_ALLOCATOR_CORRUPT, |
| 166 |
| 167 // Could not allocate histogram memory due to lack of space. |
| 168 CREATE_HISTOGRAM_ALLOCATOR_FULL, |
| 169 |
| 170 // Could not allocate histogram memory due to unknown error. |
| 171 CREATE_HISTOGRAM_ALLOCATOR_ERROR, |
| 172 |
| 173 // Histogram was of unknown type. |
| 174 CREATE_HISTOGRAM_UNKNOWN_TYPE, |
| 175 |
| 176 // Instance has detected a corrupt allocator (recorded only once). |
| 177 CREATE_HISTOGRAM_ALLOCATOR_NEWLY_CORRUPT, |
| 178 |
| 179 // Always keep this at the end. |
| 180 CREATE_HISTOGRAM_MAX |
| 181 }; |
| 182 |
| 183 // The structure used to hold histogram data in persistent memory. It is |
| 184 // defined and used entirely within the .cc file. |
| 185 struct PersistentHistogramData; |
| 186 |
| 187 // Get the next histogram in persistent data based on iterator while |
| 188 // ignoring a particular reference if it is found. |
| 189 scoped_ptr<HistogramBase> GetNextHistogramWithIgnore( |
| 190 Iterator* iter, |
| 191 Reference ignore); |
| 192 |
| 193 // Create a histogram based on saved (persistent) information about it. |
| 194 scoped_ptr<HistogramBase> CreateHistogram( |
| 195 PersistentHistogramData* histogram_data_ptr); |
| 196 |
| 197 // Record the result of a histogram creation. |
| 198 static void RecordCreateHistogramResult(CreateHistogramResultType result); |
| 199 |
| 200 // The memory allocator that provides the actual histogram storage. |
| 201 scoped_ptr<PersistentMemoryAllocator> memory_allocator_; |
| 202 |
| 203 // A reference to the last-created histogram in the allocator, used to avoid |
| 204 // trying to import what was just created. |
| 205 subtle::AtomicWord last_created_ = 0; |
| 206 |
| 207 DISALLOW_COPY_AND_ASSIGN(PersistentHistogramAllocator); |
| 208 }; |
| 209 |
| 210 } // namespace base |
| 211 |
| 212 #endif // BASE_METRICS_HISTOGRAM_PERSISTENCE_H_ |
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