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| 1 // Copyright (c) 2011 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 |
| 12 // the contents of all counters. | 12 // the contents of all counters. |
| 13 // | 13 // |
| 14 // To achieve this, StatsTable creates a shared memory segment to store | 14 // To achieve this, StatsTable creates a shared memory segment to store |
| 15 // the data for the counters. Upon creation, it has a specific size | 15 // the data for the counters. Upon creation, it has a specific size |
| 16 // which governs the maximum number of counters and concurrent | 16 // which governs the maximum number of counters and concurrent |
| 17 // threads/processes which can use it. | 17 // threads/processes which can use it. |
| 18 // | 18 // |
| 19 | 19 |
| 20 #ifndef BASE_METRICS_STATS_TABLE_H_ | 20 #ifndef BASE_METRICS_STATS_TABLE_H_ |
| 21 #define BASE_METRICS_STATS_TABLE_H_ | 21 #define BASE_METRICS_STATS_TABLE_H_ |
| 22 #pragma once | 22 #pragma once |
| 23 | 23 |
| 24 #include <string> | 24 #include <string> |
| 25 | 25 |
| 26 #include "base/base_api.h" | 26 #include "base/base_export.h" |
| 27 #include "base/basictypes.h" | 27 #include "base/basictypes.h" |
| 28 #include "base/hash_tables.h" | 28 #include "base/hash_tables.h" |
| 29 #include "base/synchronization/lock.h" | 29 #include "base/synchronization/lock.h" |
| 30 #include "base/threading/thread_local_storage.h" | 30 #include "base/threading/thread_local_storage.h" |
| 31 | 31 |
| 32 namespace base { | 32 namespace base { |
| 33 | 33 |
| 34 class BASE_API StatsTable { | 34 class BASE_EXPORT StatsTable { |
| 35 public: | 35 public: |
| 36 // Create a new StatsTable. | 36 // Create a new StatsTable. |
| 37 // If a StatsTable already exists with the specified name, this StatsTable | 37 // If a StatsTable already exists with the specified name, this StatsTable |
| 38 // will use the same shared memory segment as the original. Otherwise, | 38 // will use the same shared memory segment as the original. Otherwise, |
| 39 // a new StatsTable is created and all counters are zeroed. | 39 // a new StatsTable is created and all counters are zeroed. |
| 40 // | 40 // |
| 41 // name is the name of the StatsTable to use. | 41 // name is the name of the StatsTable to use. |
| 42 // | 42 // |
| 43 // max_threads is the maximum number of threads the table will support. | 43 // max_threads is the maximum number of threads the table will support. |
| 44 // If the StatsTable already exists, this number is ignored. | 44 // If the StatsTable already exists, this number is ignored. |
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| 187 ThreadLocalStorage::Slot tls_index_; | 187 ThreadLocalStorage::Slot tls_index_; |
| 188 | 188 |
| 189 static StatsTable* global_table_; | 189 static StatsTable* global_table_; |
| 190 | 190 |
| 191 DISALLOW_COPY_AND_ASSIGN(StatsTable); | 191 DISALLOW_COPY_AND_ASSIGN(StatsTable); |
| 192 }; | 192 }; |
| 193 | 193 |
| 194 } // namespace base | 194 } // namespace base |
| 195 | 195 |
| 196 #endif // BASE_METRICS_STATS_TABLE_H_ | 196 #endif // BASE_METRICS_STATS_TABLE_H_ |
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