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Side by Side Diff: base/metrics/stats_table.h

Issue 22911027: Pass StatsTable shared memory via global descriptors on Posix rather than using named shared memory. (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: Add empty line Created 7 years, 2 months ago
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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
129 // the thread if it is not already registered. 135 // the thread if it is not already registered.
130 static int* FindLocation(const char *name); 136 static int* FindLocation(const char *name);
131 137
132 private: 138 private:
133 class Private; 139 class Internal;
134 struct TLSData; 140 struct TLSData;
135 typedef hash_map<std::string, int> CountersMap; 141 typedef hash_map<std::string, int> CountersMap;
136 142
137 // Returns the space occupied by a thread in the table. Generally used 143 // Returns the space occupied by a thread in the table. Generally used
138 // if a thread terminates but the process continues. This function 144 // if a thread terminates but the process continues. This function
139 // does not zero out the thread's counters. 145 // does not zero out the thread's counters.
140 // Cannot be used inside a posix tls destructor. 146 // Cannot be used inside a posix tls destructor.
141 void UnregisterThread(); 147 void UnregisterThread();
142 148
143 // This variant expects the tls data to be passed in, so it is safe to 149 // This variant expects the tls data to be passed in, so it is safe to
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165 // to kMaxCounterNameLength-1 characters. 171 // to kMaxCounterNameLength-1 characters.
166 // 172 //
167 // On success, returns the counter_id for the newly added counter. 173 // On success, returns the counter_id for the newly added counter.
168 // On failure, returns 0. 174 // On failure, returns 0.
169 int AddCounter(const std::string& name); 175 int AddCounter(const std::string& name);
170 176
171 // Get the TLS data for the calling thread. Returns NULL if none is 177 // Get the TLS data for the calling thread. Returns NULL if none is
172 // initialized. 178 // initialized.
173 TLSData* GetTLSData() const; 179 TLSData* GetTLSData() const;
174 180
175 Private* impl_; 181 Internal* internal_;
176 182
177 // The counters_lock_ protects the counters_ hash table. 183 // The counters_lock_ protects the counters_ hash table.
178 base::Lock counters_lock_; 184 base::Lock counters_lock_;
179 185
180 // The counters_ hash map is an in-memory hash of the counters. 186 // The counters_ hash map is an in-memory hash of the counters.
181 // It is used for quick lookup of counters, but is cannot be used 187 // It is used for quick lookup of counters, but is cannot be used
182 // as a substitute for what is in the shared memory. Even though 188 // as a substitute for what is in the shared memory. Even though
183 // we don't have a counter in our hash table, another process may 189 // we don't have a counter in our hash table, another process may
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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