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1 // Copyright (c) 2010 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 // | 4 // |
5 // A StatsTable is a table of statistics. It can be used across multiple | 5 // A StatsTable is a table of statistics. It can be used across multiple |
6 // processes and threads, maintaining cheap statistics counters without | 6 // processes and threads, maintaining cheap statistics counters without |
7 // locking. | 7 // locking. |
8 // | 8 // |
9 // The goal is to make it very cheap and easy for developers to add | 9 // The goal is to make it very cheap and easy for developers to add |
10 // counters to code, without having to build one-off utilities or mechanisms | 10 // counters to code, without having to build one-off utilities or mechanisms |
11 // to track the counters, and also to allow a single "view" to display | 11 // to track the counters, and also to allow a single "view" to display |
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125 static const int kMaxCounterNameLength = 32; | 125 static const int kMaxCounterNameLength = 32; |
126 | 126 |
127 // Convenience function to lookup a counter location for a | 127 // Convenience function to lookup a counter location for a |
128 // counter by name for the calling thread. Will register | 128 // counter by name for the calling thread. Will register |
129 // the thread if it is not already registered. | 129 // the thread if it is not already registered. |
130 static int* FindLocation(const char *name); | 130 static int* FindLocation(const char *name); |
131 | 131 |
132 private: | 132 private: |
133 class Private; | 133 class Private; |
134 struct TLSData; | 134 struct TLSData; |
| 135 typedef hash_map<std::string, int> CountersMap; |
135 | 136 |
136 // Returns the space occupied by a thread in the table. Generally used | 137 // Returns the space occupied by a thread in the table. Generally used |
137 // if a thread terminates but the process continues. This function | 138 // if a thread terminates but the process continues. This function |
138 // does not zero out the thread's counters. | 139 // does not zero out the thread's counters. |
139 // Cannot be used inside a posix tls destructor. | 140 // Cannot be used inside a posix tls destructor. |
140 void UnregisterThread(); | 141 void UnregisterThread(); |
141 | 142 |
142 // This variant expects the tls data to be passed in, so it is safe to | 143 // This variant expects the tls data to be passed in, so it is safe to |
143 // call from inside a posix tls destructor (see doc for pthread_key_create). | 144 // call from inside a posix tls destructor (see doc for pthread_key_create). |
144 void UnregisterThread(TLSData* tls_data); | 145 void UnregisterThread(TLSData* tls_data); |
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164 // to kMaxCounterNameLength-1 characters. | 165 // to kMaxCounterNameLength-1 characters. |
165 // | 166 // |
166 // On success, returns the counter_id for the newly added counter. | 167 // On success, returns the counter_id for the newly added counter. |
167 // On failure, returns 0. | 168 // On failure, returns 0. |
168 int AddCounter(const std::string& name); | 169 int AddCounter(const std::string& name); |
169 | 170 |
170 // Get the TLS data for the calling thread. Returns NULL if none is | 171 // Get the TLS data for the calling thread. Returns NULL if none is |
171 // initialized. | 172 // initialized. |
172 TLSData* GetTLSData() const; | 173 TLSData* GetTLSData() const; |
173 | 174 |
174 typedef hash_map<std::string, int> CountersMap; | |
175 | |
176 Private* impl_; | 175 Private* impl_; |
177 | 176 |
178 // The counters_lock_ protects the counters_ hash table. | 177 // The counters_lock_ protects the counters_ hash table. |
179 Lock counters_lock_; | 178 Lock counters_lock_; |
180 | 179 |
181 // The counters_ hash map is an in-memory hash of the counters. | 180 // The counters_ hash map is an in-memory hash of the counters. |
182 // It is used for quick lookup of counters, but is cannot be used | 181 // It is used for quick lookup of counters, but is cannot be used |
183 // as a substitute for what is in the shared memory. Even though | 182 // as a substitute for what is in the shared memory. Even though |
184 // we don't have a counter in our hash table, another process may | 183 // we don't have a counter in our hash table, another process may |
185 // have created it. | 184 // have created it. |
186 CountersMap counters_; | 185 CountersMap counters_; |
187 ThreadLocalStorage::Slot tls_index_; | 186 ThreadLocalStorage::Slot tls_index_; |
188 | 187 |
189 static StatsTable* global_table_; | 188 static StatsTable* global_table_; |
190 | 189 |
191 DISALLOW_COPY_AND_ASSIGN(StatsTable); | 190 DISALLOW_COPY_AND_ASSIGN(StatsTable); |
192 }; | 191 }; |
193 | 192 |
194 } // namespace base | 193 } // namespace base |
195 | 194 |
196 #endif // BASE_METRICS_STATS_TABLE_H_ | 195 #endif // BASE_METRICS_STATS_TABLE_H_ |
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