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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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58 #include <stdint.h> | 58 #include <stdint.h> |
59 | 59 |
60 #include <map> | 60 #include <map> |
61 #include <memory> | 61 #include <memory> |
62 #include <set> | 62 #include <set> |
63 #include <string> | 63 #include <string> |
64 #include <vector> | 64 #include <vector> |
65 | 65 |
66 #include "base/base_export.h" | 66 #include "base/base_export.h" |
67 #include "base/command_line.h" | 67 #include "base/command_line.h" |
| 68 #include "base/files/file.h" |
68 #include "base/gtest_prod_util.h" | 69 #include "base/gtest_prod_util.h" |
69 #include "base/macros.h" | 70 #include "base/macros.h" |
70 #include "base/memory/ref_counted.h" | 71 #include "base/memory/ref_counted.h" |
71 #include "base/memory/shared_memory.h" | 72 #include "base/memory/shared_memory.h" |
72 #include "base/metrics/persistent_memory_allocator.h" | 73 #include "base/metrics/persistent_memory_allocator.h" |
73 #include "base/observer_list_threadsafe.h" | 74 #include "base/observer_list_threadsafe.h" |
74 #include "base/process/launch.h" | 75 #include "base/process/launch.h" |
75 #include "base/strings/string_piece.h" | 76 #include "base/strings/string_piece.h" |
76 #include "base/synchronization/lock.h" | 77 #include "base/synchronization/lock.h" |
77 #include "base/time/time.h" | 78 #include "base/time/time.h" |
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500 // If using shared memory to pass around the list of field trials, then | 501 // If using shared memory to pass around the list of field trials, then |
501 // expects |field_trial_handle_switch| command line argument to | 502 // expects |field_trial_handle_switch| command line argument to |
502 // contain the shared memory handle. | 503 // contain the shared memory handle. |
503 // If not, then create the trials as before (using the kForceFieldTrials | 504 // If not, then create the trials as before (using the kForceFieldTrials |
504 // switch). Needs the |field_trial_handle_switch| argument to be passed in | 505 // switch). Needs the |field_trial_handle_switch| argument to be passed in |
505 // since base/ can't depend on content/. | 506 // since base/ can't depend on content/. |
506 static void CreateTrialsFromCommandLine( | 507 static void CreateTrialsFromCommandLine( |
507 const base::CommandLine& cmd_line, | 508 const base::CommandLine& cmd_line, |
508 const char* field_trial_handle_switch); | 509 const char* field_trial_handle_switch); |
509 | 510 |
| 511 #if defined(OS_POSIX) && !defined(OS_NACL) && !defined(OS_MACOSX) && \ |
| 512 !defined(OS_ANDROID) |
| 513 // On POSIX systems that use the zygote, we look up the correct fd that backs |
| 514 // the shared memory segment containing the field trials by looking it up via |
| 515 // an fd key in GlobalDescriptors. Returns true on success, false on failure. |
| 516 static bool CreateTrialsFromDescriptor(int fd_key); |
| 517 #endif |
| 518 |
510 #if defined(OS_WIN) | 519 #if defined(OS_WIN) |
511 // On Windows, we need to explicitly pass down any handles to be inherited. | 520 // On Windows, we need to explicitly pass down any handles to be inherited. |
512 // This function adds the shared memory handle to field trial state to the | 521 // This function adds the shared memory handle to field trial state to the |
513 // list of handles to be inherited. | 522 // list of handles to be inherited. |
514 static void AppendFieldTrialHandleIfNeeded( | 523 static void AppendFieldTrialHandleIfNeeded( |
515 base::HandlesToInheritVector* handles); | 524 base::HandlesToInheritVector* handles); |
| 525 #elif defined(OS_POSIX) |
| 526 // On POSIX, we also need to explicitly pass down this file descriptor that |
| 527 // should be shared with the child process. Returns kInvalidPlatformFile if no |
| 528 // handle exists or was not initialized properly. |
| 529 static PlatformFile GetFieldTrialHandle(); |
516 #endif | 530 #endif |
517 | 531 |
518 // Adds a switch to the command line containing the field trial state as a | 532 // Adds a switch to the command line containing the field trial state as a |
519 // string (if not using shared memory to share field trial state), or the | 533 // string (if not using shared memory to share field trial state), or the |
520 // shared memory handle + length. | 534 // shared memory handle + length. |
521 // Needs the |field_trial_handle_switch| argument to be passed in since base/ | 535 // Needs the |field_trial_handle_switch| argument to be passed in since base/ |
522 // can't depend on content/. | 536 // can't depend on content/. |
523 static void CopyFieldTrialStateToFlags(const char* field_trial_handle_switch, | 537 static void CopyFieldTrialStateToFlags(const char* field_trial_handle_switch, |
524 base::CommandLine* cmd_line); | 538 base::CommandLine* cmd_line); |
525 | 539 |
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551 static size_t GetFieldTrialCount(); | 565 static size_t GetFieldTrialCount(); |
552 | 566 |
553 private: | 567 private: |
554 // Allow tests to access our innards for testing purposes. | 568 // Allow tests to access our innards for testing purposes. |
555 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, InstantiateAllocator); | 569 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, InstantiateAllocator); |
556 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, AddTrialsToAllocator); | 570 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, AddTrialsToAllocator); |
557 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, | 571 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, |
558 DoNotAddSimulatedFieldTrialsToAllocator); | 572 DoNotAddSimulatedFieldTrialsToAllocator); |
559 | 573 |
560 #if defined(OS_WIN) | 574 #if defined(OS_WIN) |
561 // Takes in |handle| that should have been retrieved from the command line and | 575 // Takes in |handle_switch| from the command line which represents the shared |
562 // creates a SharedMemoryHandle from it, and then calls | 576 // memory handle for field trials, parses it, and creates the field trials. |
563 // CreateTrialsFromSharedMemory(). Returns true on success, false on failure. | 577 // Returns true on success, false on failure. |
564 static bool CreateTrialsFromWindowsHandle(HANDLE handle); | 578 static bool CreateTrialsFromHandleSwitch(const std::string& handle_switch); |
565 #endif | 579 #endif |
566 | 580 |
| 581 // Takes an unmapped SharedMemoryHandle, creates a SharedMemory object from it |
| 582 // and maps it with the correct size. |
| 583 static bool CreateTrialsFromSharedMemoryHandle(SharedMemoryHandle shm_handle); |
| 584 |
567 // Expects a mapped piece of shared memory |shm| that was created from the | 585 // Expects a mapped piece of shared memory |shm| that was created from the |
568 // browser process's field_trial_allocator and shared via the command line. | 586 // browser process's field_trial_allocator and shared via the command line. |
569 // This function recreates the allocator, iterates through all the field | 587 // This function recreates the allocator, iterates through all the field |
570 // trials in it, and creates them via CreateFieldTrial(). Returns true if | 588 // trials in it, and creates them via CreateFieldTrial(). Returns true if |
571 // successful and false otherwise. | 589 // successful and false otherwise. |
572 static bool CreateTrialsFromSharedMemory( | 590 static bool CreateTrialsFromSharedMemory( |
573 std::unique_ptr<base::SharedMemory> shm); | 591 std::unique_ptr<base::SharedMemory> shm); |
574 | 592 |
575 // Instantiate the field trial allocator, add all existing field trials to it, | 593 // Instantiate the field trial allocator, add all existing field trials to it, |
576 // and duplicates its handle to a read-only handle, which gets stored in | 594 // and duplicates its handle to a read-only handle, which gets stored in |
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620 | 638 |
621 // List of observers to be notified when a group is selected for a FieldTrial. | 639 // List of observers to be notified when a group is selected for a FieldTrial. |
622 scoped_refptr<ObserverListThreadSafe<Observer> > observer_list_; | 640 scoped_refptr<ObserverListThreadSafe<Observer> > observer_list_; |
623 | 641 |
624 // Allocator in shared memory containing field trial data. Used in both | 642 // Allocator in shared memory containing field trial data. Used in both |
625 // browser and child processes, but readonly in the child. | 643 // browser and child processes, but readonly in the child. |
626 // In the future, we may want to move this to a more generic place if we want | 644 // In the future, we may want to move this to a more generic place if we want |
627 // to start passing more data other than field trials. | 645 // to start passing more data other than field trials. |
628 std::unique_ptr<FieldTrialAllocator> field_trial_allocator_ = nullptr; | 646 std::unique_ptr<FieldTrialAllocator> field_trial_allocator_ = nullptr; |
629 | 647 |
630 #if defined(OS_WIN) | |
631 // Readonly copy of the handle to the allocator. Needs to be a member variable | 648 // Readonly copy of the handle to the allocator. Needs to be a member variable |
632 // because it's needed from both CopyFieldTrialStateToFlags() and | 649 // because it's needed from both CopyFieldTrialStateToFlags() and |
633 // AppendFieldTrialHandleIfNeeded(). | 650 // AppendFieldTrialHandleIfNeeded(). |
634 HANDLE readonly_allocator_handle_ = nullptr; | 651 PlatformFile readonly_allocator_handle_ = kInvalidPlatformFile; |
635 #endif | |
636 | 652 |
637 // Tracks whether CreateTrialsFromCommandLine() has been called. | 653 // Tracks whether CreateTrialsFromCommandLine() has been called. |
638 bool create_trials_from_command_line_called_ = false; | 654 bool create_trials_from_command_line_called_ = false; |
639 | 655 |
640 DISALLOW_COPY_AND_ASSIGN(FieldTrialList); | 656 DISALLOW_COPY_AND_ASSIGN(FieldTrialList); |
641 }; | 657 }; |
642 | 658 |
643 } // namespace base | 659 } // namespace base |
644 | 660 |
645 #endif // BASE_METRICS_FIELD_TRIAL_H_ | 661 #endif // BASE_METRICS_FIELD_TRIAL_H_ |
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