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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 | 22 |
23 #include <string> | 23 #include <string> |
24 | 24 |
25 #include "base/base_export.h" | 25 #include "base/base_export.h" |
26 #include "base/basictypes.h" | 26 #include "base/basictypes.h" |
27 #include "base/containers/hash_tables.h" | 27 #include "base/containers/hash_tables.h" |
| 28 #include "base/memory/shared_memory.h" |
28 #include "base/synchronization/lock.h" | 29 #include "base/synchronization/lock.h" |
29 #include "base/threading/thread_local_storage.h" | 30 #include "base/threading/thread_local_storage.h" |
30 | 31 |
31 namespace base { | 32 namespace base { |
32 | 33 |
33 class BASE_EXPORT StatsTable { | 34 class BASE_EXPORT StatsTable { |
34 public: | 35 public: |
35 // Create a new StatsTable. | 36 // Create a new StatsTable. |
36 // If a StatsTable already exists with the specified name, this StatsTable | 37 // If a StatsTable already exists with the specified name, this StatsTable |
37 // will use the same shared memory segment as the original. Otherwise, | 38 // will use the same shared memory segment as the original. Otherwise, |
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109 // Gets the sum of the values for a particular counter for a given pid. | 110 // Gets the sum of the values for a particular counter for a given pid. |
110 // If the counter does not exist, creates the counter. | 111 // If the counter does not exist, creates the counter. |
111 int GetCounterValue(const std::string& name, int pid); | 112 int GetCounterValue(const std::string& name, int pid); |
112 | 113 |
113 // The maxinum number of counters/rows in the table. | 114 // The maxinum number of counters/rows in the table. |
114 int GetMaxCounters() const; | 115 int GetMaxCounters() const; |
115 | 116 |
116 // The maxinum number of threads/columns in the table. | 117 // The maxinum number of threads/columns in the table. |
117 int GetMaxThreads() const; | 118 int GetMaxThreads() const; |
118 | 119 |
| 120 #if defined(OS_POSIX) |
| 121 // Get the underlying shared memory handle for the table. |
| 122 base::SharedMemoryHandle GetSharedMemoryHandle() const; |
| 123 #endif |
| 124 |
119 // The maximum length (in characters) of a Thread's name including | 125 // The maximum length (in characters) of a Thread's name including |
120 // null terminator, as stored in the shared memory. | 126 // null terminator, as stored in the shared memory. |
121 static const int kMaxThreadNameLength = 32; | 127 static const int kMaxThreadNameLength = 32; |
122 | 128 |
123 // The maximum length (in characters) of a Counter's name including | 129 // The maximum length (in characters) of a Counter's name including |
124 // null terminator, as stored in the shared memory. | 130 // null terminator, as stored in the shared memory. |
125 static const int kMaxCounterNameLength = 64; | 131 static const int kMaxCounterNameLength = 64; |
126 | 132 |
127 // Convenience function to lookup a counter location for a | 133 // Convenience function to lookup a counter location for a |
128 // counter by name for the calling thread. Will register | 134 // counter by name for the calling thread. Will register |
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184 // have created it. | 190 // have created it. |
185 CountersMap counters_; | 191 CountersMap counters_; |
186 ThreadLocalStorage::Slot tls_index_; | 192 ThreadLocalStorage::Slot tls_index_; |
187 | 193 |
188 DISALLOW_COPY_AND_ASSIGN(StatsTable); | 194 DISALLOW_COPY_AND_ASSIGN(StatsTable); |
189 }; | 195 }; |
190 | 196 |
191 } // namespace base | 197 } // namespace base |
192 | 198 |
193 #endif // BASE_METRICS_STATS_TABLE_H_ | 199 #endif // BASE_METRICS_STATS_TABLE_H_ |
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