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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 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 // FieldTrial is a class for handling details of statistical experiments | 5 // FieldTrial is a class for handling details of statistical experiments |
6 // performed by actual users in the field (i.e., in a shipped or beta product). | 6 // performed by actual users in the field (i.e., in a shipped or beta product). |
7 // All code is called exclusively on the UI thread currently. | 7 // All code is called exclusively on the UI thread currently. |
8 // | 8 // |
9 // The simplest example is an experiment to see whether one of two options | 9 // The simplest example is an experiment to see whether one of two options |
10 // produces "better" results across our user population. In that scenario, UMA | 10 // produces "better" results across our user population. In that scenario, UMA |
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262 // Returns the trial name and selected group name for this field trial via | 262 // Returns the trial name and selected group name for this field trial via |
263 // the output parameter |field_trial_state|, but only if the trial has not | 263 // the output parameter |field_trial_state|, but only if the trial has not |
264 // been disabled. In that case, true is returned and |field_trial_state| is | 264 // been disabled. In that case, true is returned and |field_trial_state| is |
265 // filled in; otherwise, the result is false and |field_trial_state| is left | 265 // filled in; otherwise, the result is false and |field_trial_state| is left |
266 // untouched. | 266 // untouched. |
267 bool GetState(State* field_trial_state); | 267 bool GetState(State* field_trial_state); |
268 | 268 |
269 // Adds the field trial to the allocator whose memory is to be shared with | 269 // Adds the field trial to the allocator whose memory is to be shared with |
270 // child processes. Assumes the calling code has a lock around the call to | 270 // child processes. Assumes the calling code has a lock around the call to |
271 // this function, since the check for the allocator is not thread-safe. | 271 // this function, since the check for the allocator is not thread-safe. |
272 void AddToAllocatorWhileLocked( | 272 void AddToAllocatorWhileLocked(SharedPersistentMemoryAllocator* allocator); |
273 base::SharedPersistentMemoryAllocator* allocator); | |
274 | 273 |
275 // Returns the group_name. A winner need not have been chosen. | 274 // Returns the group_name. A winner need not have been chosen. |
276 std::string group_name_internal() const { return group_name_; } | 275 std::string group_name_internal() const { return group_name_; } |
277 | 276 |
278 // The name of the field trial, as can be found via the FieldTrialList. | 277 // The name of the field trial, as can be found via the FieldTrialList. |
279 const std::string trial_name_; | 278 const std::string trial_name_; |
280 | 279 |
281 // The maximum sum of all probabilities supplied, which corresponds to 100%. | 280 // The maximum sum of all probabilities supplied, which corresponds to 100%. |
282 // This is the scaling factor used to adjust supplied probabilities. | 281 // This is the scaling factor used to adjust supplied probabilities. |
283 const Probability divisor_; | 282 const Probability divisor_; |
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316 bool group_reported_; | 315 bool group_reported_; |
317 | 316 |
318 // Whether this trial is registered with the global FieldTrialList and thus | 317 // Whether this trial is registered with the global FieldTrialList and thus |
319 // should notify it when its group is queried. | 318 // should notify it when its group is queried. |
320 bool trial_registered_; | 319 bool trial_registered_; |
321 | 320 |
322 // When benchmarking is enabled, field trials all revert to the 'default' | 321 // When benchmarking is enabled, field trials all revert to the 'default' |
323 // group. | 322 // group. |
324 static bool enable_benchmarking_; | 323 static bool enable_benchmarking_; |
325 | 324 |
325 // Reference to related field trial struct and data in shared memory. | |
326 SharedPersistentMemoryAllocator::Reference ref_; | |
Alexei Svitkine (slow)
2016/10/25 19:18:53
Nit: Move this above the static var above - so all
lawrencewu
2016/10/25 20:27:33
Done.
| |
327 | |
326 DISALLOW_COPY_AND_ASSIGN(FieldTrial); | 328 DISALLOW_COPY_AND_ASSIGN(FieldTrial); |
327 }; | 329 }; |
328 | 330 |
329 //------------------------------------------------------------------------------ | 331 //------------------------------------------------------------------------------ |
330 // Class with a list of all active field trials. A trial is active if it has | 332 // Class with a list of all active field trials. A trial is active if it has |
331 // been registered, which includes evaluating its state based on its probaility. | 333 // been registered, which includes evaluating its state based on its probaility. |
332 // Only one instance of this class exists. | 334 // Only one instance of this class exists. |
333 class BASE_EXPORT FieldTrialList { | 335 class BASE_EXPORT FieldTrialList { |
334 public: | 336 public: |
335 // Year that is guaranteed to not be expired when instantiating a field trial | 337 // Year that is guaranteed to not be expired when instantiating a field trial |
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519 | 521 |
520 // Remove an observer. | 522 // Remove an observer. |
521 static void RemoveObserver(Observer* observer); | 523 static void RemoveObserver(Observer* observer); |
522 | 524 |
523 // Notify all observers that a group has been finalized for |field_trial|. | 525 // Notify all observers that a group has been finalized for |field_trial|. |
524 static void NotifyFieldTrialGroupSelection(FieldTrial* field_trial); | 526 static void NotifyFieldTrialGroupSelection(FieldTrial* field_trial); |
525 | 527 |
526 // Return the number of active field trials. | 528 // Return the number of active field trials. |
527 static size_t GetFieldTrialCount(); | 529 static size_t GetFieldTrialCount(); |
528 | 530 |
531 // Return the field trial allocator (for adding to it). | |
532 static SharedPersistentMemoryAllocator* GetFieldTrialAllocator(); | |
533 | |
529 private: | 534 private: |
530 // Allow tests to access our innards for testing purposes. | 535 // Allow tests to access our innards for testing purposes. |
531 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, InstantiateAllocator); | 536 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, InstantiateAllocator); |
532 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, AddTrialsToAllocator); | 537 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, AddTrialsToAllocator); |
533 | 538 |
534 // Expects a mapped piece of shared memory |shm| that was created from the | 539 // Expects a mapped piece of shared memory |shm| that was created from the |
535 // browser process's field_trial_allocator and shared via the command line. | 540 // browser process's field_trial_allocator and shared via the command line. |
536 // This function recreates the allocator, iterates through all the field | 541 // This function recreates the allocator, iterates through all the field |
537 // trials in it, and creates them via CreateFieldTrial(). | 542 // trials in it, and creates them via CreateFieldTrial(). |
538 static void CreateTrialsFromSharedMemory( | 543 static void CreateTrialsFromSharedMemory( |
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576 // Entropy provider to be used for one-time randomized field trials. If NULL, | 581 // Entropy provider to be used for one-time randomized field trials. If NULL, |
577 // one-time randomization is not supported. | 582 // one-time randomization is not supported. |
578 std::unique_ptr<const FieldTrial::EntropyProvider> entropy_provider_; | 583 std::unique_ptr<const FieldTrial::EntropyProvider> entropy_provider_; |
579 | 584 |
580 // List of observers to be notified when a group is selected for a FieldTrial. | 585 // List of observers to be notified when a group is selected for a FieldTrial. |
581 scoped_refptr<ObserverListThreadSafe<Observer> > observer_list_; | 586 scoped_refptr<ObserverListThreadSafe<Observer> > observer_list_; |
582 | 587 |
583 // Allocator used to instantiate field trial in child processes. In the | 588 // Allocator used to instantiate field trial in child processes. In the |
584 // future, we may want to move this to a more generic place if we want to | 589 // future, we may want to move this to a more generic place if we want to |
585 // start passing more data other than field trials. | 590 // start passing more data other than field trials. |
586 std::unique_ptr<base::SharedPersistentMemoryAllocator> | 591 std::unique_ptr<SharedPersistentMemoryAllocator> field_trial_allocator_ = |
587 field_trial_allocator_ = nullptr; | 592 nullptr; |
588 | 593 |
589 #if defined(OS_WIN) | 594 #if defined(OS_WIN) |
590 // Readonly copy of the handle to the allocator. Needs to be a member variable | 595 // Readonly copy of the handle to the allocator. Needs to be a member variable |
591 // because it's needed from both CopyFieldTrialStateToFlags() and | 596 // because it's needed from both CopyFieldTrialStateToFlags() and |
592 // AppendFieldTrialHandleIfNeeded(). | 597 // AppendFieldTrialHandleIfNeeded(). |
593 HANDLE readonly_allocator_handle_ = nullptr; | 598 HANDLE readonly_allocator_handle_ = nullptr; |
594 #endif | 599 #endif |
595 | 600 |
596 DISALLOW_COPY_AND_ASSIGN(FieldTrialList); | 601 DISALLOW_COPY_AND_ASSIGN(FieldTrialList); |
597 }; | 602 }; |
598 | 603 |
599 } // namespace base | 604 } // namespace base |
600 | 605 |
601 #endif // BASE_METRICS_FIELD_TRIAL_H_ | 606 #endif // BASE_METRICS_FIELD_TRIAL_H_ |
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