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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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